System and method for high-end electronic start switch assembly for split-start single-phase induction motor of household dryer

Abstract

The invention discloses an electronic switch assembly and a control method of a split-phase starting single-phase induction motor for a household clothes dryer. The assembly comprises an MCU, the MCU is loaded with a real-time algorithm software control program, and the starting speed state of the motor can be detected by analyzing and processing the change of steady-state positive sequence amplitude current in the starting process. Based on real-time positive sequence amplitude current analysis processing, the MCU calculates and detects an overspeed condition in real time, disconnects an auxiliary winding and connects a heater element so as to accurately control the transition of the motor to single-phase operation until a rated rotating speed is reached. Based on real-time positive sequence amplitude voltage and current analysis and processing, the overload condition of rated rotor speed reduction can be detected, and the auxiliary winding can be switched on again to maintain the operation performance of the motor. The assembly includes a housing having a heat sink for efficient thermal management and overheating protection of electronic devices. And an effective, reliable and low-cost solution is provided for the operation of the efficient clothes dryer by ensuring the accurate control on the starting and operating conditions of the motor and the overload protection.

Description

Technical Field

[0001] This application relates to the field of electronic starting switches, and more particularly to a system and method for a high-end electronic starting switch assembly for a split-phase starting single-phase induction motor used in a household clothes dryer. Background Art

[0002] This disclosure relates to the operation control of a split-phase starting single-phase induction motor for a household clothes dryer or other applications. It relates to an electronic starting switch assembly and a control method for effectively starting and controlling a split-phase induction motor. This electronic starting switch assembly can be used to operate a household clothes dryer, including turning on a heater such as an electric heater when the motor speed reaches above a specific motor speed, and turning off the heater whenever the speed drops below a specific speed. This electronic starting switch assembly and control method are an ideal solution to replace the traditional mechanical centrifugal switch used in split-phase induction motor applications.

[0003] For decades, split-phase induction motors have dominated the drive applications of household clothes dryers. In a laundry room, a mechanical centrifugal starting switch plays a crucial role in operating a household clothes dryer paired with a washing machine. The mechanical centrifugal starting switch can effectively start a split-phase induction motor after the motor speed reaches a certain speed. When the motor reaches above a specific rotor speed, it can effectively turn on the heater of the dryer, and turn off the heater whenever the speed is below this speed, which provides a reliable safety guarantee for the laundry load heated in the dryer and protects the laundry load in the dryer from being damaged due to overheating. Usually, whenever the motor speed is below a certain speed, the rotation speed of the dryer drum slows down, resulting in a reduction in the airflow through the laundry load inside the drum. If the heater is not turned off in time, it may cause potential overheating problems for the laundry.

[0004] A split-phase motor is a single-phase induction motor having a main or running winding and an auxiliary or starting winding; the two windings are distributed such that their neutral lines are offset from each other by 90 electrical degrees. The auxiliary winding has a higher ratio of stator resistance to inductance than the main winding to achieve the so-called split-phase effect. As is well known, at the stationary zero-speed condition, if only the main winding is powered, no torque is generated. Therefore, to start the rotor, both windings are energized to produce torque. Then, after the rotor reaches a speed typically around 75% to 80% of the synchronous speed, the main winding alone can produce almost as much torque as the two-phase winding, so the auxiliary winding has to be disconnected. In addition, at higher speeds between 80% and 90% of the synchronous speed of the motor, the split-phase motor with both windings powered produces less torque. Therefore, from the perspective of torque generation, the auxiliary winding is cut off at the "overspeed" point when the motor speed reaches approximately 75% to 80% of the synchronous speed. Another reason for disconnecting the auxiliary winding is to prevent the motor from consuming too much power in watts, and if the auxiliary winding remains in the circuit for too long, it may burn out or damage the starting winding or other components.

[0005] In addition, in many applications to improve the starting torque capability, capacitor-start motors are often used, and in this case, the functional accuracy and effectiveness of the centrifugal starting switch are even more critical. This is because above the "overspeed" point speed of the starting switch, the capacitor voltage increases rapidly, and if the motor reaches this speed and operates for a relatively long time, the capacitor is extremely likely to be damaged and cause other faults to occur.

[0006] For split-phase induction motors and capacitor-start induction motors, the task of the starting switch is usually to disconnect the auxiliary winding at the "overspeed" point speed. For decades, traditional mechanical centrifugal starting switches have provided a fairly effective solution for split-phase induction motors and capacitor-start motors used in household appliances and fractional-horsepower motor applications due to their relatively low cost. However, the problems with centrifugal starting switches are also obvious. Since the mechanical starting switch includes relay components to connect and disconnect inductive loads, this generates sparks. This is especially problematic for situations where there may be exposure to natural gas or liquefied gas leaks, such as the operation of a dryer heater in a basement workshop. In addition, the spark effect on the switch contacts may cause the mechanical starting switch to fail, reducing the service life of the motor. Additionally, from a production perspective, the mechanical switch components can increase the difficulty of manufacturing process control (such as the precision control of weight components and multiple adjustment steps), which slows down production and thus results in higher costs.

[0007] Although less common, there are some split-phase induction motors that use electronic starting switches instead of centrifugal starting switches. However, electronic starting switches face challenges in terms of reliability and cost-effectiveness. For example, the prior art of electronic starting switches used in combination with water pumps only provides limited solutions for fractional-horsepower split-phase induction motors, where the load is more predictable and fixed. Due to this predictability, previous electronic starting switches used timing control to start the switch at the "overspeed" point speed. However, in many applications such as household clothes dryers, the load (e.g., the clothing load) is highly variable, and thus an electronic switch that only controls time cannot meet the technical requirements because generally, the larger the load, the longer the starting time required. Substantially, for applications with variable loads, timing-based control is not reliable. There is a need for a more reliable, low-cost, and effective electronic starting switch assembly from an application perspective, which includes advanced control methods to achieve efficient and accurate operation of household clothes dryers and other applications. Summary of the Invention

[0008] The electronic starting switch assembly disclosed herein includes a microprocessor unit (MCU), a memory, a sensing circuit system, and a power electronics switch assembly. This MCU is configured to execute a control method implementing the present invention. This control method can detect the state of the motor starting speed by analyzing and processing the change in the steady-state positive-sequence amplitude current during the starting process. The MCU calculates the "overspeed" condition and stores the overspeed condition in the memory, and this overspeed condition is used to control the power electronics switch assembly to control the disconnection of the auxiliary winding and the connection of the heater element when the overspeed condition is met.

[0009] During operation, the MCU detects the state and performance of the motor, calculates the positive-sequence amplitude voltage and current, and detects potential overload operating conditions that may cause the rotor speed to drop below a predetermined threshold value. If an overload condition is detected, the system can reconnect the auxiliary winding to restore normal motor performance.

[0010] The present disclosure also includes a power electronics switch assembly housing that supports a printed circuit board (PCB) and includes a heat sink, and the shape of the heat sink is designed to match the airflow of the motor to improve heat dissipation. The housing is also designed to protect the electronic components from environmental damage, ensuring the life and reliability of the assembly.

[0011] Before explaining the embodiments of the present invention in detail, it should be understood that the present invention is not limited to the operating details or structural details, nor to the arrangement of components set forth in the following description or shown in the drawings. The present invention can be implemented in various other embodiments and can be practiced or carried out in alternative ways not explicitly disclosed herein. In addition, it should be understood that the wording and terms used herein are for the purpose of description and should not be regarded as restrictive. The use of "comprising" and "including" and their variants is intended to cover the items listed hereinafter and their equivalents, as well as additional items and their equivalents. In addition, enumeration may be used in the description of various embodiments. Unless otherwise explicitly stated, the use of enumeration should not be construed as limiting the present invention to any particular order or number of components. The use of enumeration should also not be construed as excluding any additional steps or components that may be combined with or incorporated into the enumerated steps or components. Any reference to claim elements such as "at least one of X, Y, and Z" means including any one of X, Y, or Z individually, as well as any combination of X, Y, and Z, such as X, Y, Z; X, Y; X, Z; and Y, Z. Description of the Drawings

[0012] Figure 1 An example diagram of a split-phase induction motor for a household clothes dryer application is shown, which shows an electronic starting switch assembly that includes an electronic starting switch for a split-phase motor of a household clothes dryer and a corresponding clothes dryer heater switch.

[0013] Figure 2A An exploded view of a split-phase motor of a household clothes dryer according to an embodiment of the present disclosure is shown.

[0014] Figure 2B A front view of the motor pulley side showing the electronic starting switch assembly is shown.

[0015] Figure 3A A front view of the electronic starting switch assembly showing the terminal numbers is shown.

[0016] Figure 3B A side view of the electronic starting switch assembly is shown, and the air flow direction through the fan blade is shown.

[0017] Figure 4 A block diagram of control functions and logic functions according to an embodiment of the present disclosure is shown.

[0018] Figure 5A An example sensing circuit for sensing the voltage of the main winding is shown.

[0019] Figure 5B An example sensing circuit for sensing the voltage of the auxiliary winding is shown.

[0020] Figure 5C Shows an exemplary sensing circuit for sensing the phase current of the main winding.

[0021] Figure 5D Shows an exemplary sensing circuit for sensing the phase current of the auxiliary winding.

[0022] Figure 6A Shows an exemplary drive and power electronic switch circuit for starting a split-phase motor.

[0023] Figure 6B Shows an exemplary drive and power electronic switch circuit for turning on / off the dryer heater and buzzer.

[0024] Figure 7A Shows an exemplary complete geometric model for finite element analysis of a split-phase induction motor for a household clothes dryer.

[0025] Figure 7B Shows a whole-pole geometric model of a split-phase induction motor in a finite element analysis (FEA).

[0026] Figure 8 Shows an exemplary circuit diagram of a split-phase induction motor control system for application with finite element analysis (FEA) processing.

[0027] Figure 9A Presents exemplary finite element analysis (FEA) simulation results showing the main, auxiliary, and total input current waveforms of a split-phase induction motor of a household clothes dryer in a locked-rotor state.

[0028] Figure 9B Shows exemplary FEA simulation results showing the output torque characteristics over time of a split-phase induction motor of a household clothes dryer in a locked state.

[0029] Figure 10 Shows the relationship between theoretical torque characteristics and speed, showing the positive-sequence torque, negative-sequence torque, and resultant torque of a single-phase winding motor.

[0030] Figure 11 Shows an exemplary analysis reference coordinate system axis system, showing the synchronous speed d-q axis coordinate system and the static two-phase a-b axis coordinate system, where phase A is aligned with the main winding and phase B is in the opposite direction of the auxiliary winding.

[0031] Figure 12A Shows exemplary FEA simulation results showing the main winding phase current and auxiliary winding phase current at speeds from 0 to 1800 RPM during the first second of startup time.

[0032] Figure 12BShows exemplary FEA simulation results showing the reference phase A and phase B currents at speeds from 0 to 1800 RPM during the first second of start-up time.

[0033] Figure 13A Shows exemplary FEA simulation results showing the transformed synchronous speed coordinate d-q axis current waveforms at speeds from 0 to 1800 RPM during the first second of start-up time.

[0034] Figure 13B Shows exemplary FEA simulation results showing the filtered d-q axis currents, positive sequence DC current components, and positive sequence magnitude currents at speeds from 0 to 1800 RPM during the first second of start-up time.

[0035] Figure 14A Shows exemplary FEA simulation results showing the transformed negative sequence synchronous speed coordinate d-q axis current waveforms at speeds from 0 to 1800 RPM during the first second of start-up time.

[0036] Figure 14B Shows exemplary FEA simulation results showing the filtered negative sequence d-q axis currents, negative sequence (or second harmonic) DC current components, and negative sequence (or second harmonic) magnitude currents at speeds within the range from 0 to 1800 RPM during the first second of start-up time.

[0037] Figure 15 Shows exemplary FEA simulation results showing the main winding phase magnitude current curve and the auxiliary winding phase magnitude current curve at speeds within the range from 0 to 1800 RPM during the first second of start-up time.

[0038] Figure 16A Shows exemplary FEA simulation results showing the main phase magnitude current curve as the envelope of the main winding current waveform at speeds within the range from 0 to 1800 RPM during the first second of start-up time.

[0039] Figure 16B Shows exemplary FEA simulation results showing the auxiliary winding phase magnitude current curve as the envelope of the auxiliary winding current waveform at speeds within the range from 0 to 1800 RPM during the first second of start-up time.

[0040] Figure 17 Shows test and simulation results showing the relationship between the rotor start-up speed rise curve and time of a split-phase induction motor under different loads.

[0041] Figure 18A Shows test and simulation results showing the relationship between the starting positive sequence magnitude current curve and time of a split-phase induction motor under different loads.

[0042] Figure 18B Shows the test and simulation results, showing the relationship between the starting main winding amplitude current curve and time of a split-phase induction motor under different loads.

[0043] Figure 19A Shows the test and simulation results, showing the relationship between the starting main winding current waveform and time of a split-phase induction motor under no-load.

[0044] Figure 19B Shows the test and simulation results, showing the relationship between the starting auxiliary winding current waveform and time of a split-phase induction motor under no-load.

[0045] Figure 20A Shows the test and simulation results, showing the relationship between the starting positive-sequence amplitude current waveform and time of a split-phase induction motor under different voltages at full load.

[0046] Figure 20B Shows the test and simulation results, showing the relationship between the starting positive-sequence amplitude current waveform and speed of a split-phase induction motor under different voltages at full load.

[0047] Figure 21A Shows the test and simulation results, showing the relationship between the starting positive-sequence amplitude current and voltage curves and the per-unit speed of a split-phase induction motor at full load.

[0048] Figure 21B Shows the test and simulation results, showing the relationship between the starting positive-sequence impedance curve and the per-unit speed of a split-phase induction motor at full load.

[0049] Figure 22 Shows the control algorithm logic flowchart of an electronic switch module for a household dryer.

[0050] Figure 23A Shows the test and simulation results, showing the relationship between the starting and normal operating speed curves and time of a split-phase induction motor under load conditions.

[0051] Figure 23B Shows the test and simulation results, showing the relationship between the main current and auxiliary current and time of a split-phase induction motor under load conditions.

[0052] Figure 24A Shows the test and simulation results, showing the relationship between the starting positive-sequence amplitude current curve and time of a split-phase induction motor under load conditions.

[0053] Figure 24B Shows the test and simulation results, showing the relationship between the starting positive-sequence amplitude impedance curve and time of a split-phase induction motor under load conditions.

[0054] Figure 24C Shows test and simulation results, showing the relationship between the positive sequence magnitude voltage curve of a split-phase induction motor and time under load conditions. Detailed implementation

[0055] I. Split-phase induction motor of a clothes dryer;

[0056] Figure 1 Shows an example diagram of a split-phase induction motor 10 of a household clothes dryer having an electronic starting switch assembly 15 according to the present disclosure. In this example, the split-phase induction motor 10 includes a rotor 11 (e.g., a squirrel-cage rotor), a main winding or running winding 12, and an auxiliary winding or starting winding 13. The auxiliary winding 13 has a higher ratio of stator resistance to inductance compared to that of the main winding 12 to achieve a phase-splitting effect. When both windings are connected to a voltage L1, such as 120 VAC 14, an elliptical rotating magnetic field is generated in the air gap to start the motor. When the rotor speed reaches about 75% to 80% of the synchronous speed, the microprocessor in the electronic starting switch assembly 15 disconnects the auxiliary winding 13 from the voltage L1. At this time, the torque is generated only by the magnetic field of the main winding 12, thereby driving the rotor speed to the rated speed.

[0057] In the current implementation, the electronic starting switch assembly 15 includes two power electronic switches 16, 17. The auxiliary winding power electronic switch 16 is configured to selectively connect the auxiliary winding 13 to its voltage source L1 or disconnect the auxiliary winding 13 from its voltage source L1, thereby effectively allowing the auxiliary winding 13 to be selectively connected to or disconnected from the split-phase induction motor in the stator circuit 5. The clothes dryer heater power electronic switch 17 is configured to selectively connect the clothes dryer heater to its voltage source L2 or disconnect the clothes dryer heater from its voltage source L2, thereby effectively turning on or off the clothes dryer heater.

[0058] For the electronic starting switch assembly 15 to sense that the rotor 11 has reached the "overspeed" speed, the auxiliary winding power electronic switch 16 disconnects the auxiliary winding 13 from the split-phase motor stator circuit 5. Additionally, for household clothes dryer operation, when the motor 10 reaches or exceeds the "overspeed" speed threshold, the electronic starting switch assembly 15 turns on another power electronic switch 17 to connect the clothes dryer heater 18 to the L2 voltage source 19 of the clothes dryer heater circuit 6 to turn on the clothes dryer heater 18. If the speed of the rotor 11 drops below the "overspeed" speed, the clothes dryer heater power electronic switch 17 disconnects the clothes dryer heater 18 from the L2 voltage source 19 (usually 240 VAC).

[0059] The electronic starting switch assembly 15, which includes both the auxiliary winding power electronic switch 16 and the dryer heater power electronic switch 17, can be controlled by a microcontroller. The microcontroller can be included in the electronic starting switch assembly 15 and can control the operation of one or both of the power electronic switches 16, 17 based on appropriate criteria (e.g., comparison between a "runaway" speed point stored in a memory and the detected feedback). The heater on / off time can be controlled and adjusted based on the requirements of the dryer operation, which provides control characteristics that cannot be achieved by a conventional centrifugal switch. Figure 1 Points A on the main winding 12 and point B on the auxiliary winding 13 illustrate suitable measurement points for signal sensing targets.

[0060] Example details regarding the technical aspects of the electronic starting switch assembly 15 used with a split-phase induction motor to control a household clothes dryer according to the present disclosure are described below.

[0061] When powered, the electronic starting switch assembly 15 connects both the main winding 12 and the auxiliary winding 13 to the power supply 14L1 (usually a voltage of 120VAC), and this generates sufficient torque to cause the motor to rotate.

[0062] The microprocessor of the electronic starting switch module 15 can detect the rotor speed by sensing the current and / or voltage across the windings 12, 16. When the speed of the rotor 11 reaches a specific threshold value stored in the memory (e.g., 75% to 80% of the synchronous speed), the microprocessor of the electronic starting switch assembly 15 can communicate with the power electronic switch 16 to disconnect the auxiliary winding 13 from the L1 voltage source 14 120VAC. Additionally, when the speed of the rotor 11 reaches this threshold value (or a different threshold value stored in the memory), the microprocessor of the electronic starting switch assembly 15 can communicate with the power electronic switch 17 to connect the dryer heater 18 to the L2 high voltage power supply 19 240VAC.

[0063] The amount of load contained inside the drum of a household clothes dryer is highly variable, ranging from a relatively light load (e.g., less than one pound) to a relatively heavy load (e.g., over 32 pounds). The starting time from zero to the runaway speed point depends largely on the load size. This means that the starting method with a preset fixed time for turning on and off the auxiliary winding is usually ineffective. Instead, the present disclosure utilizes the real-time detection result of the rotor speed achieved by the electronic starting switch assembly to determine the disconnection of the auxiliary winding 13. This is different from the timing-based method, which takes into account the influence of variable loads. Additionally, the dryer heater 18 can also be turned on using the same rotor speed runaway point and the power supply.

[0064] After the rotor speed reaches or exceeds the overspeed point speed, since the dryer load tumbles inside the drum, any unexpected load change (such as a wet cotton sheet that has absorbed a certain amount of water) may generate an additional torque load, instantly pulling the rotor speed back below the overspeed point speed. In this case, the microprocessor of the electronic starting switch assembly 15 can sense the drop in rotor speed and command the auxiliary winding power electronic switch 16 to reconnect the auxiliary winding back into the circuit to increase the torque again, so that the speed of the rotor 11 increases again and exceeds the overspeed point. In this way, the microcontroller in the electronic starting switch assembly 15 not only detects that the rotor speed exceeds the overspeed point, but can also be configured to sense and detect when the rotor speed drops below the overspeed point, even after the auxiliary winding has been disconnected from the 120VAC circuit by the power electronic switch 16. The power electronic switch 17 that controls the dryer heater 18 takes corresponding actions. For example, the microcontroller can also control the dryer heater electronic switch 17 to disconnect the dryer heater from the voltage source when the rotor speed drops below the overspeed point, thereby turning off the dryer heater. In addition, the electronic starting switch assembly 15 of the present disclosure provides various potential functions for controlling a household dryer or a household clothes dryer, which are not possible with a conventional mechanical starting switch. For example, since the electronic starting switch assembly 15 can not only be set to effectively control the disconnection or connection of each power electronic switch in response to real-time detection of the rotor speed according to the size of the load, at the same time, the electronic power switch components 16 and 17 can selectively connect and disconnect the auxiliary winding and the dryer heater based on pre-programmed instructions, such as lag or extension. These pre-programmed instructions are all implemented based on the rotor speed detection information.

[0065] Therefore, any starting method configured to operate based on only a one-time timing delay (that is, the starting method only disconnects the auxiliary winding once) is not feasible for household clothes dryer applications.

[0066] II. Electronic switch assembly and assembly;

[0067] Figures 2A to 2B A plurality of perspective views showing an embodiment of a split-phase induction motor assembly 400 for a household clothes dryer according to the present disclosure are shown, and the split-phase induction motor assembly includes an electronic starting switch assembly. Figure 2A A disassembled pulley-side exploded view of the motor assembly 400 is depicted, and Figure 2B A front assembled perspective view of the motor assembly 400 showing the electronic starting switch assembly 402 is depicted.

[0068] The depicted embodiment of the electric motor 400 has a pulley side end cover assembly 401 that includes a pulley side end cover frame structure, fastening screws, and a hub ring 413. The electronic starting switch assembly 402 includes an electronic starting switch assembly PCB printed circuit board 403 and a housing 404 for mounting the PCB. The electronic starting switch assembly PCB 403 has terminals that are connected to different power sources (e.g., 120VAC and 240VAC) and a dryer heater to operate a household dryer. The cast aluminum housing 404 can include a space for protecting the PCB inside and a heat sink for dissipating heat generated when the electronic switch components operate. The stator winding includes a main winding 405 and an auxiliary winding 406, both of which are embedded in main and auxiliary winding distribution slots that are 90 electrical degrees apart. The shaft and bearing system 407 has one shaft and two bearing assemblies to provide a rotating assembly. The stator core 408 can be made of silicon steel material to provide a main magnetic field path and accommodate the winding structure. The motor rotor 409 includes a squirrel cage structure with an aluminum cast rotor winding that has slot conductor bars and end rings 410. The end rings 410 of the rotor can have fan blades that generate an air flow that passes over the heat sink of the electronic switch assembly 402. The fan impeller 411 can generate an air flow in the environment around the electric motor to improve the overall heat dissipation condition around the motor. The rear end cover 412 can have a structure similar to the pulley side end cover. Figure 2B A pulley side view of the assembled one is shown. The pulley side end cover includes a hub ring 413 and four frame arms. Two top frame arms 414 have two end arm structures for mounting an electronic switch module.

[0069] Figure 3A A perspective view of an exemplary embodiment of the electronic starting switch assembly 402 is shown. The assembly includes one or more microprocessors 444 (also referred to as a control system, controller, or microcontroller unit MCU), an electronic printed circuit board PCB 403, and a housing 404 that can be made of cast aluminum. The MCU together with other related electronic components (e.g., sensors and memories) can be included within the MCU or separately mounted on the PCB to perform sensing, driving, and other functions, enabling control algorithms to be implemented to operate the electronic starting switch assembly 402.

[0070] The PCB 403 has on-board connection terminals that can be the same as those used in a typical centrifugal starting switch of a household clothes dryer for application compatibility. That is, by providing the same number and arrangement of terminals as a conventional centrifugal starting switch, the centrifugal starting switch assembly can be easily replaced by the electronic starting switch assembly of the present disclosure. The terminals on the centrifugal switch parts are typically numbered 2-6-4-3-5-1. Specifically, terminal one 426 and terminal two 421 are connection terminals for the dryer heater, terminal four 423 and terminal five 425 are terminals for the main winding connection, and terminal three 424 and terminal four 423 are terminals for the auxiliary winding connection (based on the starting speed state). Terminal six 422 is a terminal for connecting the buzzer circuit system 427. The buzzer circuit system can be configured to generate an audible sound when the dryer operation is completed.

[0071] Figures 3A to 3B The illustrated electronic starting switch assembly 402 includes a housing 404. In this example, the housing 404 provides a location space for mounting a printed circuit board (PCB) 431, which houses the electronic devices of the electronic starting switch assembly and also includes an integral heat sink 430 for mounting the PCB and dissipating the heat generated by the electronic components. Generally, a typical household clothes dryer heater can consume about 5 kW of power at a current of about 20 amperes. To provide proper heat dissipation, the heat sink 430 can have a special shape to fit into the space around the limited pulley side end cover of the motor, so that the motor with the electronic switch assembly installed can be installed in the household clothes dryer unit without any interference. Specifically, the space envelope can be Figure 2B the span between the two end frame arms 414 of the pulley side end cover, and as Figure 2B shown, the angular area space from the motor stator end winding to the hub ring 413.

[0072] In addition, Figures 3A to 3B views of the electronic starting switch assembly 402 are shown, including a front view and a side view. The heat sink 430 includes a front body 434 and side faces 432. The shape of the heat sink is suitable for the limited space and is exactly mounted on the two-arm frame of the end cover. The middle heat sink fins have a higher height, and the heat sink fins on both sides have a lower height to adapt to the space shape and the mounting position. The heat sink can be fixed with screws on the brackets on both sides, achieving easy installation and integration with the end cover structure. The shape of the heat sink is conducive to effective heat dissipation in the limited space. The number of heat sink fins, the gap width, and other heat sink parameters can be varied to provide the required heat dissipation performance.

[0073] The electronic starting switch assembly 402 can implement various additional functions. For example, the radiator 430 can be integrated with or combined with the housing 404 for supporting the PCB 403. The area above the PCB spanning the length and width of the wall of the housing 404 can be referred to as a pool housing, which can be filled with glue, resin, or other suitable materials to protect the components of the electronic starting switch assembly from damage caused by moisture, vibration, or other environmental impacts. The potting process can also improve reliability, safety, and heat dissipation performance. The overall dimensions of the housing 404 can be adjusted according to the distance from the stator end winding 405 and the pulley ring 413 (e.g., as Figures 2A to 2B shown). Additionally, considering the air flow direction around the motor, the fins of the radiator can be parallel to the motor axial direction to utilize the directional air flow 433 generated by the fan blades on the rotor end ring to pass through each fin to improve heat dissipation and maintain the PCB temperature appropriately. Furthermore, as Figure 3B shown, additional side wings 432 can be added to increase the effective surface area of the air flow. This is an example of a radiator housing combination suitable for the installation space of a typical split-phase motor in a household clothes dryer, and this example combination provides sufficient air flow area and helps to maintain the temperature of the electronic switch assembly appropriately.

[0074] The electronic starting switch assembly can have combinations of different electronic components, including but not limited to one or more power supplies, one or more power electronic switch circuits, sensing and drive circuitry, and a controller. Referring to Figure 4 , a representative block diagram of an embodiment of the electronic starting switch assembly of the present disclosure is depicted. This figure depicts two power supplies (low voltage supply L1 and high voltage supply L2), two power electronic switch circuits (low voltage power electronic switch circuit 441 and high voltage power electronic switch circuit 443), sensing and drive circuitry 442, and a microprocessor unit (MCU) 444.

[0075] The low voltage power electronic switch circuit 441 can selectively connect or disconnect the connection between the L1 low voltage power supply and the auxiliary winding of the split-phase motor. Additionally, the low voltage power electronic switch circuit 441 can selectively connect or disconnect the connection between the L1 low voltage power supply and the buzzer 427. The high voltage power electronic switch circuit 443 can selectively connect or disconnect the L2 high voltage power supply to the clothes dryer heater 18. Substantially, depending on the drive electronic switch circuits 441, 443, they can connect or disconnect the power supply voltage to certain circuit components, such as the auxiliary winding, buzzer, and dryer heater.

[0076] The microprocessor 444 collaborates with the sensing and driving circuitry 442 to effectively control the power electronic switch circuits 441, 443. The microprocessor 444 can receive the sensed motor state characteristics from the sensing and driving circuitry 442, and the microprocessor 444 issues drive commands to the sensing and driving circuitry 442 according to the control logic of the programmed control algorithm. For clarity and ease of understanding, in the figure, the sensing and driving circuitry 422 is placed together. However, it should be understood that the sensing and driving circuitry can be separate components or independent circuits that separately implement the sensing and driving functions.

[0077] The sensing circuitry 442 or the microprocessor 444 can effectively detect the rotor speed based on one or more variables among the main winding voltage and current and the auxiliary winding voltage and current. The microprocessor 444 can be programmed to respond to the rotor speed when the rotor reaches or exceeds the "overspeed" point. For example, the controller 444 can be programmed to disconnect the auxiliary winding 406 from the L1 low voltage source, so that the motor generates more torque. The controller 444 can also be programmed to connect the L2 high voltage source to the dryer heater 18, effectively powering on the dryer heater. The controller 444 can also control the power electronic switch circuits 441, 443 based on other factors. For example, the microprocessor 444 and the sensing and driving circuitry 442 can collaborate to connect the L1 low voltage source to the buzzer 427 in response to the expiration of a timer, so that the buzzer generates a sound (e.g., beep) to indicate that the dryer operation is complete, which is a popular function of a household clothes dryer. Although the power electronic switch circuits 441, 443 are Figure 4 shown as a single element in the figure, it should be understood that each of them can include multiple discrete power electronic switch circuit components. For example, the low voltage power electronic switch circuit 441 can include two discrete power electronic switch circuits that can independently and separately connect the L1 low power voltage to the buzzer 427 and the motor main / auxiliary windings 405, 406. Substantially, the power supply and switch component circuitry is controlled by the MCU 444 through the corresponding driving circuitry.

[0078] The sensing and driving circuitry 442 and the microcontroller (MCU) 444 share a DC voltage source VCC( Figure 4of 442). The sensing and drive circuit system 442 can include a sensing circuit system capable of detecting various main winding and auxiliary winding characteristics 470. In this example, the sensing circuit system 442 can detect the main winding phase voltage, the main winding phase current, the auxiliary winding phase voltage, and the auxiliary winding phase current. That is, the hardware configuration of the drive and sensing circuit system 442 can be used to implement the implementation of the rotor starting speed characteristic detection method. In another alternative embodiment, the sensing circuit system 442 can include a circuit system for sensing additional, different, or simplified circuits.

[0079] The microprocessor 444 can include a memory that can contain various operating parameters related to the split-phase motor characteristic starting method. For example, the memory can include one or more motor parameters, control coefficients, such as Figures 11 to 1 the values depicted in FIG. 4. The microprocessor 444 can include a plurality of I / O ports to receive analog signals and process them inside the controller to execute algorithms and programs, and output commands to the drive circuit system 442 to operate electronic switch components, such as turning on or off the auxiliary winding, the dryer heater, the buzzer, or a combination thereof.

[0080] The microprocessor 444 can be configured with a starting control method. That is, the software, programming, and / or logic on the microprocessor can be configured with a motor characteristic starting control method, including the following functions:

[0081] 1) When powered on, the microprocessor 444 sends commands to the low-voltage switch components 16, 441 of the switch assembly 402 to connect both the main windings 12, T4-423, T5-425 and the auxiliary windings 13, T3-424 to the L1 power supply 14 (120VAC) to rotate the motor rotor.

[0082] 2) When the speed of the rotor 11 reaches the "overspeed" point speed, the microprocessor commands the drive circuit system 442 to operate the switch components 16, 441 of the electronic starting switch assembly 15, 402 to disconnect the auxiliary winding 13 from the L1 power supply (120VAC). At the same time, the microprocessor commands the drive circuit system 442 to operate the switch component 17, 443 to connect the dryer heater 18 to the L2 power supply (240VAC) to turn on the dryer heater to the power supply.

[0083] 3) After the speed exceeds the "overspeed" starting point, the controller 444 can process the real-time feedback signal 470 by the sensing circuit system 442 to detect the speed and determine whether any unexpected torque load instantaneously pulls the rotor speed below the "overspeed" point. For the case of returning to "overspeed", the switching circuits 16, 441 can reconnect the auxiliary windings 13, 424 to the split-phase motor stator circuit 5 to increase the torque again to restart the rotor 11, 409, and then this will speed up again beyond the "overspeed" speed. Thus, the electronic starting switch assemblies 15, 402 of the present disclosure can not only detect exceeding the "overspeed" speed point during the initial start-up, but also detect the rotor speed and respond if the rotor speed drops below this overspeed (e.g., at any time after the initial start-up period ends). The electronic switch components 17, 443 for controlling the dryer heater 18 can be configured to take corresponding actions based on the change of the "overspeed" speed, such as turning on and off the dryer heater according to whether the rotor speed is above or below the "overspeed" speed point.

[0084] 4) When the household dryer finishes the drying work, the controller 444 can command the low-voltage switching circuit 441 to operate the buzzer 427 to generate an audio indication (e.g., beeping sound) to prompt the user near the dryer that the dryer operation has been completed. The low-voltage electronic power switching circuit 441 can include a dedicated normally closed or normally open switch that can be activated to selectively connect the buzzer 427.

[0085] Figures 5A to 5D A schematic diagram of an exemplary sensing circuit system 442 of the electronic starting switch assembly 402 according to the present disclosure is depicted. This includes but is not limited to the main winding voltage sensing circuit Figure 5A 、the auxiliary winding voltage sensing circuit Figure 5B 、the main winding current sensing circuit Figure 5C and the auxiliary winding current sensing circuit Figure 5D . From a topological perspective, the voltage sensing circuits of both the main winding and the auxiliary winding have the same configuration and can sense the real-time voltage at a specific sampling rate.

[0086] Referring to Figure 5A , the main winding voltage 470 can be sensed between point A and ground to measure the voltage drop across the entire split-phase motor circuit. As Figure 5AAs shown, it can be achieved by a suitable combination of circuit components that sense parameters, such as the combination of resistors (R11A, R11B, R11C) and capacitor C11 connected in the circuit shown in the figure. By selecting suitable values for the resistors and the capacitor, the voltage sensing bandwidth can be set to a range from 0 volts to the rated voltage of 120 VAC or higher, such as 140 VAC. Here, 140 VAC is the overvoltage value defined for a household clothes dryer. The analog signal generated by the sensing circuit system can be sent to one of the I / O ports of the MCU 444 for performing control algorithms.

[0087] Referring to Figure 5B , the auxiliary winding voltage 470 can be sensed between point B and ground to measure the voltage drop across the two ends of the auxiliary winding 13. It should be noted that even when the motor is running and the auxiliary winding is disconnected from the rotor circuit due to the electronic starting switch assembly 15 turning on switches 16, 441, this voltage measurement includes the back electromotive force generated by the rotating field. As Figure 5B depicted, this can be achieved by a suitable combination of circuit components that sense parameters, such as the combination of resistors (R12A, R12B, R12C) and capacitor C12 connected as shown in the figure. By selecting suitable values for the resistors and the capacitor, the voltage sensing bandwidth can be set to the desired range, such as from 0 volts to 140 volts. The analog signal generated by the sensing circuit system can be sent to one of the I / O ports of the MCU 444 for performing control algorithms.

[0088] The main winding current feedback signal 470 can be sensed by the Figure 5C sensing circuit shown. The main winding current passes through a combination of resistors and capacitors (for example, resistors R13A, R13B, R13C and capacitor C13), and this combination of resistors and capacitors has appropriately selected parameters to transmit a suitable current sensing range (such as from 0.1 ampere to 25 amperes) by converting the current sensing range into an analog DC voltage range of 0 VDC to 3.3 VDC or 5.0 VDC. The analog voltage signal representing the sensed current through the main winding can be electrically transmitted to one of the I / O ports of the MCU 444 for performing the split-phase induction motor control algorithm.

[0089] The auxiliary winding current feedback signal 470 can be sensed by Figure 5DThe sensing circuit shown senses. The auxiliary winding current passes through a combination of resistors and capacitors (e.g., resistors R14A, R14B, R13C and capacitor C14), which has appropriately selected parameters to convey a suitable current sensing range (e.g., from 0.1 ampere to 5 amperes) by converting the current sensing range to an analog DC voltage range of 0 VDC to 3.3 VDC or 5.0 VDC. The analog voltage signal representing the sensed current through the auxiliary winding can be electrically transmitted to one of the I / O ports of the MCU 444 for performing a split-phase induction motor control algorithm.

[0090] Figures 6A to 6B A diagram depicting an exemplary embodiment of the drive circuit system 442 and the electronic switch components 441, 443, which selectively connect the auxiliary winding to the split-phase induction motor stator circuit 5 and supply power to the dryer heater 18, respectively.

[0091] Figure 6A A hardware circuit implementation method showing a part of the electronic starting switch assembly, including the circuitry related to Figure 4 the low-voltage power electronic switch circuit 441 and the drive circuit system 442. The circuitry of the embodiment depicted in the present disclosure includes a triac 51, an optocoupler 52, and a set of resistors R11, R11A1, R11B1. For an on / off command signal from the MCU 444 (e.g., a signal generated based on a split-phase induction motor starting control algorithm executed on a microprocessor), the optocoupler 52 generates an electrical control signal Q1 that controls the triac 51, effectively connecting the L1 low-voltage source to the auxiliary winding 13 or disconnecting the auxiliary winding 13 from the L1 low-voltage source according to the state of the control signal Q1. If needed, resistors and other circuit components can be included to provide biasing, current limiting, and other circuit functions.

[0092] Figure 6BA hardware circuit implementation method showing a part of an electronic starting switch assembly 402 is presented, which includes circuitry related to a low-voltage power electronic switch circuit 441, a high-voltage power electronic switch circuit 443, and a drive circuit system 442. In particular, the circuit diagram shows the drive and electronic switches for controlling both the dryer heater 18 and the buzzer 427. The circuit system is configured to be connected in series with a similar circuit architecture, including: two triacs Q2 56, Q3 60, each triac acting as an electronic switch for controlling the current flow from the L2 and L1 voltage sources respectively; two optocouplers 57, 61; and resistors R11, R11A2, R11B2, R11A3, R11B3. In response to an on / off command signal from the MCU 444 (such as a signal generated based on a split-phase induction motor starting control algorithm executed on the controller), the optocouplers 57, 61 each generate corresponding electrical control signals Q2, Q3 for controlling their respective triacs 56, 60, effectively connecting the L1 low-voltage source to the buzzer 427 or disconnecting the L1 low-voltage source from the buzzer 427 and connecting the L2 high-voltage source to the heater 18 or disconnecting the L2 high-voltage source from the heater 18 according to the states of the control signals Q2, Q3. If needed, resistors and other circuit components can be included to provide biasing, current limiting, and other circuit functions. Substantially, the MCU 444 provides control commands based on a software algorithm to turn on / off the dryer heater, thereby causing the optocouplers 57, 61 to turn on / off the triacs Q2 and Q3 simultaneously to connect the heater to the power source L2 and connect the buzzer to the power source L1 respectively. The buzzer circuit system can be configured in various different ways to provide the desired functions, such as activating the buzzer in response to the completion of the dryer operation or when the dryer is operating at other predetermined stages.

[0093] III. Split-phase motor FEA model and analysis;

[0094] The present disclosure provides a novel starting speed detection method. By using the novel starting speed detection method, an electronic starting switch can be utilized to start a split-phase induction motor. For example, the electronic starting switch assembly can replace the mechanical centrifugal switch in a household dryer. The electronic starting switch assembly can operate based on the following electrical variables: including but not limited to the voltage and current of the main winding and the auxiliary winding, or other electrical variables of the split-phase induction motor. These electrical variables can be sensed by a sensing circuit system for performing starting algorithms for analysis and processing. Various characteristics that can be used to operate and control the split-phase induction motor of a household dryer are discussed herein. For example, several split-phase induction motor starting algorithms used in combination with the electronic starting switch assembly according to the present disclosure will be discussed herein.

[0095] According to the analysis theory of single-phase induction motors, ideally, if two symmetrical windings are displaced by 90 electrical degrees from each other, a circular rotating field will be generated when the motor is powered by two symmetrical voltages. The two symmetrical voltages have the same amplitude and a phase angle of 90 electrical degrees between them. However, in a split-phase induction motor, the main winding and the auxiliary winding are displaced by 90 electrical degrees from each other and have significantly different impedances, thus producing a phase-splitting effect. When powered by a voltage, the currents in the main winding and the auxiliary winding are different in terms of amplitude and phase angle, which results in the generation of an elliptical rotating field instead of a circular rotating field.

[0096] In addition, it should be noted that the starting characteristics of the motor are usually affected by transient processes. These processes may be influenced by changes in motor parameters, which may be caused by the saturation of the silicon steel material in the motor core. Since the classical motor analysis methods based on fixed parameters and equivalent circuits may not be able to fully consider these constraints and characteristics, it may be more appropriate to apply high-end advanced methods for detecting the starting speed of the motor.

[0097] A. FEA analysis model and control circuit;

[0098] The finite element analysis (FEA) method is used to study the starting characteristics of complex magnetic field and circuit systems. Figure 7A Shows a complete geometric model of a split-phase motor, including a stator core structure 81, a main winding 82, an auxiliary winding 83, and a rotor structure 84. The main winding and the auxiliary winding are not symmetrical because the auxiliary winding is only energized during the initial starting time (e.g., the first few seconds of motor starting). To generate a sinusoidally distributed magnetic field in the air gap, the stator slots are designed to have smaller slots 85, 86 and larger slots 87, 88 to improve the torque generating ability and the utilization rate of the stator winding material and the silicon steel core (as shown in the Figure 7B unipolar model).

[0099] Figure 8 Shows an example control circuit diagram 100 that can be coupled with the FEA model for magnetic field calculation. Substantially, Figure 8 the control circuit can be coupled and integrated with the FEA model to simulate and analyze the magnetic field inside the split-phase induction motor. The power supply voltage V L1 101 supplies power to the motor stator winding. In this FEA analysis model, there are two voltage measurement points and two current measurement points. Among the two voltage measurement points, V M 102 and V A 103 represent the measured main-phase voltage and auxiliary-phase voltage, respectively. Among the two current measurement points, I M 104 and I A 105 represent the main-phase current and auxiliary-phase current, respectively. The inductances L Ml 106 and L Al107 represents the leakage inductance at the ends of the main winding and the auxiliary winding. Resistors R M and R A represent the resistance of the main winding and the resistance of the auxiliary winding. Inductors L M and L A represent the inductance of the main winding and the inductance of the auxiliary winding respectively. The auxiliary winding switch S_Aux 112 allows the auxiliary winding to be selectively connected or disconnected from other circuit parts.

[0100] B. FEA analysis simulation and test results;

[0101] Real-time simulation of the locked-rotor operating state to study the characteristics of the split-phase induction motor of a household clothes dryer. Figure 9A The current waveforms of the total input current 121, the main winding current 122, and the auxiliary winding current 123 versus time in the locked-rotor state are shown. The amplitudes of the main winding current and the auxiliary winding current are different and have a small phase angle difference, so the motor generates an elliptical field around the air gap. As Figure 9B shown, the elliptical field can generate a torque with additional torque fluctuations, Figure 9B depicting the relationship between the torque characteristics and time 124 in the locked-rotor operating state. The torque curve 124 shows that due to the split-phase effect, there is sufficient average torque to start the motor. However, the elliptical field also generates a significant torque amplitude superimposed on the average torque.

[0102] The FEA model of this system couples the non-linear field calculation with the control circuit, providing a powerful means and method for studying the dynamic characteristics of the split-phase motor of a household clothes dryer. To simulate the dynamic characteristics, a series of non-linear field calculations can be performed to explore the transient characteristics during the real-time starting process. The simulation results are verified through tests on the split-phase motor system of a household clothes dryer. The FEA model and the real-time system simulation method can effectively utilize these electrical variables (e.g., the voltages and currents of the main winding and the auxiliary winding associated with the rotor speed) for the detection of the starting speed.

[0103] IV. Positive-sequence current and negative-sequence current in the synchronous d-q coordinate system;

[0104] Theoretically, when an AC voltage is applied to one phase winding of a single-phase motor, it only generates a pulsating field in the air gap. This pulsating field can be divided into two rotating fields in the frequency domain: the positive-sequence field and the negative-sequence field. Both the positive-sequence field and the negative-sequence field generate their corresponding torques.

[0105] Figure 10Describes the relationship between the torque and speed characteristics of both positive-sequence torque and negative-sequence torque. The positive-sequence torque characteristic curve 131 is similar to that of a typical three-phase induction motor in the forward rotation direction. In contrast, the negative-sequence torque characteristic curve 132 has the same general shape as the positive-sequence torque characteristic curve but in the opposite direction. The combination of positive torque and negative torque produces a single-phase winding torque curve 133, showing zero output torque at zero speed.

[0106] When the motor is assisted by an external force or torque in either direction (e.g., the positive direction or the negative direction), the single-phase winding motor generates sufficient torque to rotate the rotor to the load operating point 134. This helps to explain why split-phase induction motors utilize special starting control methods. Thus, when the single-phase winding motor rotates, for example, at the operating point 134, both positive-sequence torque and negative-sequence torque exist simultaneously. Therefore, both positive-sequence (forward) current and negative-sequence (reverse) current exist simultaneously in the frequency domain.

[0107] Therefore, whether both the main winding and the auxiliary winding are energized or only the main winding is connected while the auxiliary winding is disconnected, the split-phase motor can be analyzed as a standard two-phase winding motor. By dealing with it in this way, advanced multiphase motor control coordinate system transformation methods can be applied to study the characteristics and explore new speed detection methods during the starting process.

[0108] Combined Figure 11 describes the relationship between the main winding and the auxiliary winding in the motor stator reference coordinate system. Since the main winding and the auxiliary winding are displaced 90 electrical degrees from each other, the main winding 141 is defined as being aligned with the A-phase coordinate system 142 represented by V a and i a . The auxiliary winding 143 is defined as being aligned with the axis leading the main winding axis by 90 electrical degrees. In addition, the B-phase coordinate system 144 is defined as being represented by V b and i b and lagging the A-phase coordinate system by 90 electrical degrees. Therefore, the B-phase coordinate system is aligned in the opposite direction of the auxiliary winding, which means that the B-phase axis lags the auxiliary winding by 180 electrical degrees (as Figure 11 shown).

[0109] When the PARK transformation is applied to introduce the synchronous speed reference coordinate system d-q axes 145, 146, the positive-sequence current and the negative-sequence current are transformed from the time domain to the frequency domain (as Figure 10As shown. The fundamental positive sequence or forward current is converted into DC component variables on the d-q axes 145, 146 of the coordinate system. That is, when the positive sequence current (AC current) is viewed in the synchronous reference coordinate system (d-q axes), the positive sequence current appears as a DC value rather than an oscillating value. At the same time, the negative sequence reverse current appears as a second harmonic current that can be decoupled from the fundamental current (DC component) and filtered out using appropriate filtering techniques. The real-time continuous positive sequence DC current can be used to detect the starting speed of the split-phase induction motor of a household dryer. In short, the change of the real-time continuous positive sequence or forward DC current during the starting process can be used to accurately detect the starting speed of the split-phase induction motor of a household clothes dryer.

[0110] A. Positive sequence current calculation;

[0111] Based on the application of the Park transformation to the two-phase system, the currents of phase A 142 and phase B 144 are transformed into the d-q axis currents of the synchronous speed coordinate system as follows:

[0112]

[0113] Where,

[0114] i d : The d-axis current on the d-q axes of the synchronous speed coordinate system,

[0115] iq: The q-axis current on the d-q axes of the synchronous speed coordinate system,

[0116] i a : The current of the phase A winding,

[0117] i b : The current of the phase B winding.

[0118] Since the phase B winding 144 lags the phase A winding 142 by 90 electrical degrees, and the auxiliary winding 143 leads the main winding 141 by 90 electrical degrees, the relationship between the two winding currents and the two-phase currents can be defined as,

[0119] i a (t) = i M (t) (2)

[0120] i b (t) = -k AM ·i A (t) (3)

[0121] Where,

[0122]

[0123] i M : The phase current of the main winding,

[0124] i A : Auxiliary winding current,

[0125] k AM : Effective winding turns ratio between the auxiliary winding and the main winding,

[0126] W A : Total number of turns in series of the auxiliary winding,

[0127] W M : Total number of turns in series of the main winding,

[0128] k dp1A : Fundamental winding coefficient of the auxiliary winding,

[0129] k dp1M : Fundamental winding coefficient of the main winding.

[0130] Variables on the d-q axes of the reference synchronous speed coordinate system. The positive-sequence current component is represented by the DC current component, while the negative-sequence current component can be expressed as a second-harmonic component that can be filtered out. Therefore, the DC current component is the positive-sequence current in the d-q axes of the synchronous speed coordinate system,

[0131]

[0132] where the function int(f, t) is an integral function that can be expressed as follows,

[0133]

[0134] i d0 : Positive-sequence current on the d-axis in the d-q axes of the coordinate system,

[0135] i q0 : Positive-sequence current on the q-axis in the d-q axes of the coordinate system,

[0136] T 2 : Time period of the second harmonic.

[0137] On the d-q axes of the synchronous speed coordinate system, the positive-sequence DC current component is the current that can be approximately calculated as follows,

[0138]

[0139] Finally, at time t, the positive-sequence amplitude current is calculated as follows,

[0140]

[0141] where,

[0142] I m0 : Positive-sequence amplitude current in the d-q axes of the coordinate system.

[0143] An example calculation of the positive-sequence current of a split-phase motor in a household clothes dryer can be simulated under the following conditions: the rotor speed ranges from 0 to the synchronous speed of 1800 RPM, and the auxiliary winding is always connected to the power supply. Figure 12A Shows the simulation results, showing Figure 12B Compared with the phase A current 163 and phase B current 164 in the a-b axis coordinate system shown, the main-phase current 161 and the auxiliary-winding phase current 162 at speeds from 0 to 1800 RPM during a starting time of 1 second. The relationship between the phase B current 164 defined in Equation 3 and the auxiliary-winding phase current 162 is reflected in Figures 12A to 12B The current waveforms shown.

[0144] In addition, Figure 13A Shows example simulation results, the reference two-phase currents based on the synchronous-speed d-q axis coordinate system at speeds from 0 to 1800 RPM during a starting time of 1 second. In this coordinate system, both the transformed positive-sequence d-axis current 171 and q-axis current 172 use the DC component of the positive-sequence current, while the negative-sequence current appears as a second-harmonic component. Figure 13B Shows exemplary simulation results, the filtered d-q axis current waveforms to obtain a pair of DC components (i d0 , i q0 ) 173, 174, which represent the pure positive-sequence current characteristics.

[0145] The positive-sequence magnitude current I m0 Waveform 175 is directly related to Figure 10 The positive-sequence torque characteristics in the speed range of the operating point 134 shown and can be used to detect the starting speed, which will be described in more detail in the next section.

[0146] B. Calculation of negative-sequence current and main-phase magnitude current;

[0147] As mentioned before, the main-phase magnitude current consists of a positive-sequence current component and a negative-sequence current component (as Figure 10 Shown). To accurately calculate the main-phase magnitude current, the negative-sequence current should also be calculated. Applying the same method to the positive-sequence current, the negative-sequence current corresponds to the second-order component in the d-q axis coordinate system. By generating a negative d-q axis coordinate system rotating at the negative synchronous speed, the negative-sequence current can be represented as a DC component, while the positive-sequence current corresponds to the second-order component in the negative d-q coordinate system. Therefore, the negative d-q axis current can be obtained in the same way as the current obtained in the positive d-q axis coordinate system by using -θ instead of θ, and the negative d-q axis current is expressed as:

[0148]

[0149] Where,

[0150] id- : The d-axis current in the negative d-q coordinate system,

[0151] i q- : The q-axis current in the negative d-q coordinate system.

[0152] Based on the negative d-q coordinate system, after filtering the second harmonic components, the DC component of the negative d-q current or the second harmonic component of the positive d-q current can be calculated as follows:

[0153]

[0154] where,

[0155] i d2 : The d-axis second harmonic current in the d-q coordinate system,

[0156] i q2 : The q-axis second harmonic current in the d-q coordinate system,

[0157] T 2 : The period time of the second harmonic signal.

[0158] Then, the variables in the time domain can be transformed into the frequency domain. The transient currents in the two-phase a-b coordinate system can be expressed as,

[0159]

[0160] Or,

[0161]

[0162] Therefore, the magnitude currents in the two-phase a-b coordinate system in the frequency domain can be calculated as follows,

[0163]

[0164] where,

[0165] I am : The magnitude current of phase A in the a-b coordinate system,

[0166] I bm : The magnitude current of phase B in the a-b coordinate system.

[0167] Finally, the magnitude currents of the main winding phase and the auxiliary winding phase can be obtained as follows,

[0168]

[0169] where,

[0170] I M : The magnitude current of the main winding phase,

[0171] I A : Auxiliary winding phase amplitude current.

[0172] Compared with the simulation results showing the positive d-q axis coordinate system, here the current is simulated based on the negative d-q axis coordinate system to calculate the current i Figure 13A and i d- curves. q- Exemplary simulation results are shown, the i Figure 14A based on the negative synchronous speed d-q axis coordinate system at speeds from 0 to 1800 RPM during a starting time of 1 second d- 181 and i q- 182 current curves. Figure 14B Exemplary simulation results are shown, the DC current components i d2 183, i q2 184 and the amplitude i m2 185 of the negative d-q axis current after filtering out the positive sequence current, where the positive sequence current is a second harmonic current. As Figure 13B shown, as the speed increases towards the synchronous speed, the amplitude of the positive current DC component 175 decreases significantly. Conversely, as Figure 14B shown, the amplitude of the reverse current DC component 185 increases significantly.

[0173] Main winding phase amplitude current I M and auxiliary winding phase amplitude current I A can be calculated using Equation 14. Figure 15 Exemplary simulation results 190 are shown, the main winding amplitude current 191 and the auxiliary winding amplitude current 192 Figure 16A compared with the AC current waveforms 201, 202 in Figure 16B . The amplitude curves represent the envelope curves of the AC current waveforms.

[0174] V. Positive sequence amplitude current for speed detection;

[0175] The characteristics of a split-phase induction motor with a centrifugal switch used in a household clothes dryer with various wet cloth loads are analyzed. Figure 17Example test and simulation results are shown, depicting curves of speed versus time during the starting process under different load conditions. Each curve shows a different wet clothes load condition: no load 221, 1 / 4 load 222, 1 / 2 load 223, 3 / 4 load 224, and full load 225. As depicted by the curves, the length of the starting time from zero speed to the rated speed (about 1800 RPM in this case) depends on the load size. Generally, as the load increases from no load 221 to full load 225, the actual starting time increases significantly (e.g., from about 0.75 seconds to over 1.5 seconds). These differences highlight that the related method of a starting method based solely on timing is not applicable to the split-phase motor starting control of a household clothes dryer.

[0176] By studying the current characteristics in the synchronous speed d-q axis coordinate system under different load conditions, the split-phase motor starting speed detection method was further explored. Figure 18A Test and simulation results are shown, showing the positive-sequence magnitude current curves during the starting process under different load conditions from no load 241 to full load 245. When the mechanical centrifugal switch disconnects the auxiliary winding at 75% to 80% of the synchronous speed (referred to as the "overspeed" speed point), the positive-sequence magnitude current starting characteristic curve has the same or similar current values 246 before the instant of the sudden change in the current peak, and these current values are significantly different from the starting moment current value 247 and are significantly reduced. Although the starting time varies due to different load conditions, this situation occurs consistently. Therefore, the positive-sequence magnitude current I m0 can be an effective variable for detecting the rotor speed.

[0177] On the other hand, Figure 18B Test and simulation results are shown, showing the main winding magnitude current curves during the starting process under different load conditions from no load 248 to full load 252. When the mechanical centrifugal switch disconnects the auxiliary winding at the overspeed point speed, the main winding magnitude current starting characteristic curve has the same or similar current values 253 before the instant of the sudden change in the current peak. However, there is no significant difference compared with the starting moment current value 254, where the starting time is different due to the load condition. Therefore, the information provided by the main winding magnitude current for detecting the rotor starting speed is very limited.

[0178] In addition, Figures 19A to 19B Test and simulation results are shown, which show the main winding current waveform 261 and the auxiliary winding current waveform 262 during the starting process under no load conditions, highlighting the overspeed speed point moment 263. As Figure 19A shown, the change in the main winding current waveform from the starting moment to the overspeed speed point is somewhat small, which is in Figure 18BIt can also be observed in the main winding amplitude current 248. This is because as the speed increases, the positive-sequence amplitude current decreases while the negative-sequence amplitude current increases, resulting in a very small overall change in the main winding phase amplitude during starting. However, Figure 19A the main winding amplitude current 261 in Figure 18A the corresponding positive-sequence amplitude current curve 241 in

[0179] VI. Overspeed Point Detection during Starting

[0180] As described above and referring to Figure 17 and Figures 18A to 18B , an implementation of the overspeed point speed detection method during starting includes sensing and the corresponding positive-sequence amplitude current curve during starting.

[0181] By calculating Figure 18A the ratio of the positive-sequence amplitude current 246 when the auxiliary winding is disconnected in im to the starting current 247 when first powering different loads, the load relative coefficient C im (Crossover) can be defined as shown in Equation 15 to quantify these ratios. Additionally, these load relative coefficients can remain relatively consistent under different load conditions, which defines the coefficient C

[0182] with high consistency.

[0183]

[0184] Wherein,

[0185] C im (Crossover): the positive-sequence amplitude current coefficient at the overspeed point,

[0186] I m0 (Starting): the positive-sequence amplitude current just reaching stability at the starting moment,

[0187] I m0 (Crossover): the stable positive-sequence amplitude current at the overspeed point.

[0188] To develop a rod-like overspeed point velocity detection algorithm, the operating conditions of a household clothes dryer can be studied. That is, by collecting more information about the operating conditions of a household clothes dryer, the effectiveness and robustness of a specific overspeed point velocity detection algorithm can be formed, evaluated, updated, and verified.

[0189] Operating conditions that may affect the overspeed point velocity detection algorithm include voltage variations in the power supply. For example, for a household clothes dryer application, the power supply voltage can typically vary from 100 VAC to 140 VAC. Figures 20A to 20B Test and simulation results are shown, showing the characteristics of the positive sequence magnitude current curve under different voltage supplies from 100 VAC to 140 VAC.

[0190] Figure 20A Depicts the relationship between the positive sequence magnitude current curve and time under different voltage supplies of 100 VAC 281, 120 VAC 282, 132 VAC 283, and 140 VAC 284. These curves show that both the time difference of the switch and the current value have significant changes, highlighting the impact of voltage variations on the entire system. That is, Figure 20A Shows the operating condition of the auxiliary winding switch at a specific time (e.g., disconnecting the auxiliary winding from the stator circuit 1 second after startup), and potential problems such as insufficient torque to start the motor.

[0191] Figure 20B Shows the relationship between the positive sequence magnitude current curve and speed at different power supply voltages, showing the consistency of the current ratio relative to the starting current 285 at the overspeed point speed 286, which is approximately 70% of the synchronous speed. By defining the overspeed point as The auxiliary winding can be disconnected from the stator circuit before the rotor reaches approximately 70% of the synchronous speed. Figures 20A to 20B Collectively show that for a starting process that depends on the timing of the auxiliary winding switch, power supply voltage variations can have a significant impact on motor startup. In contrast, since the results obtained by the overspeed speed point detection algorithm of the positive sequence magnitude current curve are in complete agreement with the actual overspeed speed point, the starting detection algorithm is not affected by power supply voltage variations.

[0192] That is, the decreasing trajectory curve of the positive sequence magnitude current is related to the actual starting speed acceleration and can be used to detect the overspeed point speed. By detecting the real-time positive magnitude current I m0 (Open) and checking for a decrease in the positive magnitude current, the overspeed can be detected to complete the starting process of the motor, which can be expressed as,

[0193] I m0 (Open)·<·C im (Crossover)·Im0 (Starting) (16)

[0194] Among them,

[0195] I m0 (Open): The real-time positive-sequence amplitude current during the starting process after the auxiliary winding is energized.

[0196] When the positive-sequence amplitude current I m0 (Open) decreases to a value equal to or lower than the percentage of the starting current defined by the overspeed point C im (Crossover) (i.e., the rotor speed reaches the overspeed point speed), the system disconnects the auxiliary winding. Based on the synchronous speed d-q coordinate system, the positive-sequence amplitude current trajectory curve is an electrical variable of a continuous DC component, which is effective and robust for use in the starting algorithm executed by the microprocessor of the electronic switch assembly.

[0197] For different split-phase induction motors, the overspeed point or ratio C im (Crossover) can vary. For example, split-phase induction motors with different power ranges, components, and applications can have different overspeed points. The overspeed point coefficient specific to various split-phase induction motors can be determined through simulation, empirical verification, or a combination thereof.

[0198] In some embodiments, information about a series of different household clothes dryers and how to handle different loads can be collected. For most (if not all) household clothes dryers using split-phase induction motors, an accurate, general, and stable overspeed point speed detection algorithm is usually available. In addition, a control system for setting the overspeed point speed detection algorithm can be provided for each household clothes dryer. The algorithm can be adjusted based on the data collected during actual application use. In some embodiments, each type of clothes dryer unit can be adjusted based on the test data collected during research and development or during the manufacturing process to obtain a detection algorithm for the reference overspeed point speed implemented in the motor control system of a satisfactory household clothes dryer, rather than providing an overspeed point speed detection algorithm for a general dryer unit.

[0199] VII. Detection of the "Closed" Point of the Operating Speed;

[0200] Household clothes dryers typically have a large drum driven by an electric motor (usually a split-phase induction motor). The dryer drum holds a load of wet textile articles that have absorbed a certain amount of moisture. Typically, an unexpected wet lumpy load can cause the speed of the drum to drop below the overspeed point speed. To increase the speed to the normal operating speed, torque needs to be increased, so the starting algorithm process or part of it can be restarted to restore the proper speed of the clothes dryer operation. Specifically, the split-phase motor switch control algorithm can be applied. The auxiliary winding is disconnected at 70% of the synchronous speed as the "overspeed" point, and the auxiliary winding is connected at a rotor speed below 65% of the synchronous speed as the "closed" speed point. The overspeed or switch-off speed overspeed point and the switch-closed speed point can be the same, or they can be selected to be slightly offset from the rotor speed near the overspeed point to extend the running time and reduce the number of switches. In fact, during operation, whenever the motor speed drops to this "closed" speed point, the motor starting switch is turned on to accelerate the motor rotor above the overspeed point to restore single-phase operation at the rated speed.

[0201] A. Positive-sequence amplitude voltage, current, and impedance in single-phase operation

[0202] After starting, the split-phase motor of the clothes dryer will operate in a single-phase operation mode to drive the dryer drum. In this mode, only the main winding is energized and a single-phase operating current is generated, while the auxiliary winding is disconnected from the power supply. Although there is no auxiliary winding current, both the main winding and the auxiliary winding generate their respective induced voltages. By detecting the motor characteristics of single-phase operation, the operating speed can be detected instead of the detection method during starting. This method can reconnect the auxiliary winding at the defined closed speed point, thus achieving efficient and stable motor performance.

[0203] Understanding the situation of single-phase operation of the main winding throughout the starting and running processes can facilitate the improvement of the motor speed control algorithm. When the clothes dryer motor is powered on, the main winding is initially connected to a 120VAC power supply. Before connecting the auxiliary winding to start the rotor, the motor can be energized in single-phase operation. Then, the auxiliary winding can be connected to the power supply. Once the auxiliary winding is connected, the motor operates in a two-phase mode until it reaches the overspeed point, at which point the switch associated with the auxiliary winding is turned off, disconnecting the auxiliary winding. When disconnected from the power supply, the motor returns to single-phase operation to accelerate the rotor to the rated speed and then continues to drive the motor to keep the drum rotating until an overload situation is detected or the dryer duty cycle is completed. The characteristics of the main winding in single-phase operation are the basis for developing various motor operating speed detection methods.

[0204] Reference Figure 11In the coordinate system defined therein, the PARK transformation is applied to the two-phase system, and the phase-A voltage 142 and phase-B voltage 144 in the a-b axis coordinate system are transformed into the d-q axis voltages in the synchronous speed coordinate system through the following formula:

[0205]

[0206] where,

[0207] V d : the d-axis voltage in the d-q axis of the coordinate system,

[0208] V q : the q-axis voltage in the d-q axis of the coordinate system,

[0209] V a : the phase-A winding voltage in the a-b axis of the static coordinate system,

[0210] V b : the phase-B winding voltage in the a-b axis of the static coordinate system.

[0211] The two-phase voltages of phase-A and phase-B can be expressed in the a-b axis of the coordinate system as:

[0212]

[0213] where,

[0214] V M : the main winding phase voltage, as shown by 102 in Figure 8 ,

[0215] V A : the auxiliary winding phase voltage, as shown by 103 in Figure 8 .

[0216] Based on the previous formulas (Equations 5 to 8) used to calculate the positive-sequence magnitude current and applying the same derivation, the positive-sequence voltage formula can be calculated as follows:

[0217]

[0218] where,

[0219] V d0 : the positive-sequence d-axis voltage in the d-q axis of the synchronous speed coordinate system,

[0220] V q0 : the positive-sequence q-axis voltage in the d-q axis of the synchronous speed coordinate system,

[0221] V m0 : the positive-sequence magnitude voltage in the d-q axis of the synchronous speed coordinate system.

[0222] Regarding the positive-sequence amplitude current in single-phase operation, the positive-sequence amplitude current in two-phase operation has been previously described. Single-phase operation is a special case of two-phase operation as represented by Formulas 1 to 4, where the auxiliary-winding phase current is zero, i b = 0, and can be expressed as:

[0223]

[0224] By applying the auxiliary-winding current i b = 0, the positive-sequence amplitude current can be calculated using Formulas 5 to 8. Therefore, whether during single-phase or two-phase operation, the positive-sequence amplitude current can be calculated and detected throughout the starting process from the moment of energizing the main winding.

[0225] Due to the variability of the power supply voltage, the concept of positive-sequence impedance is introduced to describe the motor characteristics while considering the influence of voltage variability. Based on the positive-sequence amplitude voltage and current (e.g., when the auxiliary winding is disconnected), the positive-sequence amplitude impedance is defined as:

[0226] Z m0 (t) = V m0 (t) / I m0 (t) (22)

[0227] where,

[0228] Z mo : The positive-sequence amplitude impedance in single-phase operation.

[0229] Figures 21A to 21B Examples of test and simulation results are shown for the relationship between the magnitudes of the positive-sequence voltage 303, positive-sequence currents 301, 302, and positive-sequence impedance 304 and the per-unit value speed from low speed to rated operating speed. As the speed increases from low speed to high speed, the positive-sequence amplitude voltage, positive-sequence amplitude current, and positive-sequence amplitude impedance all change significantly, and vice versa. Therefore, during normal single-phase operation, the positive-sequence amplitude voltage, current, and impedance are real-time motor characteristic variables that affect the operating speed detection method during normal single-phase operation.

[0230] B. Operating speed "closure" point detection method;

[0231] To detect the operating closure speed point, two variables can be utilized. The first variable utilizes the characteristic of the positive-sequence amplitude current versus speed as previously described in conjunction with Figure 21A . The positive-sequence amplitude current coefficient of C im (Crossover) in Formula 15 can be used to detect the overspeed point. This overspeed point detection method can also be applied to determine the operating closure speed point. The closed positive-sequence amplitude current coefficient during single-phase operation can be expressed as C im(Closing), which is defined as the current ratio of the positive-sequence magnitude current at the closing point to the positive-sequence magnitude current before starting. As Figure 21A shown in 301 of

[0232]

[0233] wherein,

[0234] C im (Closing): Positive-sequence magnitude current coefficient at the "closing" point for single-phase operation,

[0235] I m0 (Closing): Positive-sequence magnitude current at the "closing" point in single-phase operation, see Figure 21A 302 of

[0236] I m0 (Pre-start): Positive-sequence magnitude current at the "before starting" point in single-phase operation, see Figure 21A 301 of

[0237] The second variable relates to the positive-sequence magnitude impedance with respect to the speed characteristic 304, as Figure 21B shown. As the speed increases, this characteristic shows a regular increase, which provides an additional control check condition for detecting the stable operating closing speed point.

[0238] Therefore, at the normal operating speed with a load, due to the speed reduction under heavy load conditions, the following method for detecting the operating closing speed point can be used to decide to reconnect the auxiliary winding to accelerate the motor speed back to its rated speed. This method can be summarized as follows:

[0239] (1) Based on the closing positive-sequence magnitude current coefficient C im (Closing), detect the positive-sequence magnitude current and check whether the running positive-sequence magnitude current is greater than the positive-sequence magnitude current at the closing point, that is, multiply the closing positive-sequence magnitude current coefficient by the current before starting,

[0240] I m0 (Running) · > · C im (Closing) · I m0 (Pre-start) (24)

[0241] wherein,

[0242] I m0 (Running): Real-time running positive-sequence magnitude current at the single-phase operating speed.

[0243] (2) When condition (1) occurs, based on the positive-sequence magnitude impedance Z at the closing point m0 (Closing), detect the positive-sequence magnitude impedance, and whether the real-time positive-sequence magnitude impedance Z m0 (Running) of a single phase is equal to or less than Z m0 (Closing), 304. For example, as Figure 21B shown, where the positive-sequence impedance at the closing speed point is 11.6 ohms.

[0244] Z mo (Running) · ≤ · Z mo (Closing) (25)

[0245] Wherein,

[0246] Z m0 (Running): The real-time operating positive-sequence magnitude impedance at the single-phase operating speed,

[0247] Z m0 (Closing): The predetermined positive-sequence magnitude impedance at the closing speed in the single-phase operating mode.

[0248] If both of these conditions occur, it can be confirmed that the motor speed has reached a predetermined percentage of the synchronous speed (for example, 65% of the synchronous speed, which is the closing speed point in this example), and the auxiliary winding can be connected to accelerate the rotor back to the rated operating speed.

[0249] Figure 21A The positive-sequence magnitude current curves 301, 302 in Figure 21B and the positive-sequence magnitude impedance curve 304 in both show the characteristics of the split-phase motor during the starting and operating state periods, and can be pre-calculated through simulation or tests. The introduction and application of the positive-sequence magnitude impedance concept can effectively reduce the influence of changes in operating conditions such as power supply voltage changes on the detection of the closing speed point. The detection method with the above two criteria is effective and excellent for the application of split-phase motors in household clothes dryers.

[0250] Based on the power range and application, for various split-phase motors, the ratio C im (Closing) and Z m0 (Closing) may be different. To effectively determine these ratios, they can be determined based on empirical and test methods for individual split-phase motors or categories of split-phase motors.

[0251] This dual-parameter operating speed closing point detection algorithm provides a robust and reliable guarantee for rotor speed detection below the overspeed point. However, the present disclosure is not limited thereto, and this detection method is also suitable for other embodiments and variations. In one embodiment, the order of detection is changed. For example, the positive sequence impedance is effectively detected until it reaches the closing impedance, and the positive sequence magnitude current is detected until it reaches its closing point value (closing coefficient multiplied by the stable pre-start current before the auxiliary winding is connected) as a secondary condition to confirm that the operating speed closing point has been detected. As another example, in some embodiments, detecting only the forward impedance is sufficient to trigger a confident detection of the operating speed closing point. On the other hand, in some embodiments, simply comparing the positive sequence magnitude current with a threshold value (e.g., calculated based on the closing coefficient and the stable pre-start positive sequence magnitude current) is sufficient to complete the detection of the operating closing speed.

[0252] VIII. Electronic Starting Switch Control Method and Implementation;

[0253] According to the method of applying the positive sequence magnitude current and impedance concepts and definitions to detect the rotor speed in the present disclosure, the implementation of variable calculation and control algorithms may include, but is not limited to, the calculation of positive sequence magnitude voltage, current, and positive sequence magnitude impedance during the starting process and normal operation, the detection of the rotational speed in the overload situation, and the restoration of the rated speed.

[0254] Figure 22 The functional control logic flow block diagram shows an embodiment and describes how the electronic starting switch assembly executes the control method of the present disclosure to operate a household clothes dryer.

[0255] After starting at 311, the motor is powered by 120VAC at 312. The electronic starting control assembly uses a microprocessor unit (MCU) to start processing and load all parameters, including the current and voltage ratios based on C im (Crossover), C im (Closing), and Z 0m (Closing), as well as the sampling time. These ratios can be obtained in advance through simulation and test, and recorded in the MCU memory 444.

[0256] In 313, before the auxiliary winding is energized, the positive sequence magnitude current I m0 (Pre-start) is calculated for single-phase operation and stored in the memory for use in overload protection detection during normal operation. Once the auxiliary winding is connected to the power supply to start increasing the motor speed in 314, the positive sequence magnitude current I m0(Starting) As a reference to determine the overspeed point speed. In some embodiments, a moving sampling window is maintained in 316 to calculate the real-time positive-sequence magnitude current I m0 (Open) Decrease the value until the condition defined by Equation 16 is achieved in 317. At this time, in 318, the auxiliary winding is disconnected, and the heater is connected to the high-voltage power L2, 240VAC. Then, in 319, the motor enters the single-phase operation mode and drives the rotor to the rated steady speed. Meanwhile, the moving sampling window calculates the real-time positive-sequence magnitude voltage V m0 (Running), current I m0 (Running), and positive-sequence impedance Z m0 (Running) to detect the rotor speed in the single-phase operation mode in real time.

[0257] The motor remains in single-phase operation until the end of the operating cycle or an overload condition is detected. If the first closing condition represented by Equation 24 occurs in 323, the second condition represented by Equation 25 is checked in 324 to determine whether the speed is below the closing speed point. If both conditions are triggered, the speed is determined to be below the closing speed point, and the microprocessor responds accordingly. Specifically, in the current embodiment, the heater is disconnected from the power supply in 322, while the auxiliary winding is reconnected in 314 to start raising the motor rotor speed again in 314. Otherwise, the motor remains in operation without the auxiliary winding connected until the dryer operation is completed and the buzzer is triggered to signal the end of the dryer operation.

[0258] Figures 23A to 23B Shows the implementation of test and simulation results, the curves of the relationship between the speed and time, and the main winding current and auxiliary winding current during the start-up and operation of a split-phase induction motor of an electronic starting switch assembly, which is controlled by the improved dryer control algorithm of the present disclosure for a household dryer.

[0259] Figure 23A Shows the relationship between the speed characteristics and time during start-up and overload operation times to maintain the normal operating speed under the load distribution of the simulated household dryer operation. Observe Figure 23A , at start-up, in 341, the main winding of the motor is in the pre-start-up period ( Figure 22is marked as 313) and energized. Then, during operation 342, at time T1, both the main winding and the auxiliary winding are powered to start and speed up under the load conditions of a household clothes dryer. When the speed reaches the overspeed point speed at time T2, the auxiliary winding is disconnected from the circuit system. Then, in 343, the motor enters the single-phase operation mode and accelerates the rotor to the rated speed for normal clothes dryer operation. In this example, at time T3, there is a square wave pulsating torque in the rotating drum of the clothes dryer. In 344, the motor starts to reduce speed until it reaches the closed speed point at time T4. Then, the electronic switch assembly detects that the speed has dropped below the closed speed point and issues an instruction to reconnect the auxiliary winding to power to restart the motor again 345. Once the speed reaches or exceeds the overspeed point, the auxiliary winding is disconnected again. During the time period from T4 to T5, the rotor speed fluctuates up and down between the closed speed point and the overspeed point. Due to the high load torque, this acceleration and deceleration process can be repeated multiple times. However, in actual situations, because the overload is caused by an unbalanced load in the rotating dryer drum, the number of repetitions is usually very short. This is because the up-and-down action of raising and lowering the rotor speed by connecting and disconnecting the auxiliary winding has the effect of rebalancing and stabilizing the load. In addition, if the number of repeated fluctuations between the closed speed point and the overspeed point exceeds a predetermined number, the microprocessor can alarm by stopping the operation of the clothes dryer and using a buzzer or other indicator to attract the user's attention and intervene. At time T5, the overload torque disappears, the motor speed accelerates to the rated speed, and the motor returns to operate the clothes dryer in the normal single-phase operation mode until the clothes dryer work cycle is completed.

[0260] Figure 23B shows the relationship between the characteristics of the main winding current and the auxiliary winding current and time during start-up and overload operation times to maintain the normal operating speed under the load curve simulating the operation of a household clothes dryer. Observe Figure 23B the phase current. At the beginning, in 346, the main winding of the motor is at Figure 22The pre-start period marked as 313 in the figure is energized. Then, during operation to 347, at time T1, both the main winding and the auxiliary winding are energized, and the household clothes dryer starts the motor under load conditions. When the speed reaches or exceeds the overspeed point at time T2, the auxiliary winding is disconnected from the circuit. Then, the motor enters the single-phase operation mode 343 to accelerate the rotor speed to the rated speed 348 for normal clothes dryer operation. In 348, it is shown that the main winding phase current decreases and remains low during rated speed operation. At time T3, an overload condition instantaneously appears as a square wave pulse torque. In response, the motor starts to reduce speed 349, and in 349, it is shown that the main winding current increases until the closing speed point at time T4. Then, the electronic starting switch assembly detects that the speed has dropped below the closing point speed and reconnects the auxiliary winding back to the power supply and restarts the motor again 350, and the auxiliary winding phase current is shown in 350. When the speed reaches or exceeds the overspeed point, the auxiliary winding is disconnected again, and this process repeats once due to the large load torque. At time T5, the overload torque disappears, and the motor speed accelerates to the rated speed and returns to normal single-phase operation mode to operate the clothes dryer.

[0261] Figures 24A to 24C Shows the relationship between the controllable variables, positive sequence amplitude current, positive sequence amplitude voltage, and positive sequence impedance and time when starting and operating a split-phase induction motor of a household clothes dryer equipped with an electronic starting switch assembly. In this embodiment, as described above, based on Figure 11 the synchronous speed d-q axis coordinate system referenced in the figure calculates these variables simultaneously and in real time during the entire operation of the household clothes dryer.

[0262] Figures 24A to 24B Respectively show the relationship between the positive sequence amplitude current and positive sequence impedance and time during starting and overload operation to maintain the normal operating speed under the load curve simulating the operation of a household clothes dryer. In Figure 24A it, at the start of starting, in 361, the main winding of the motor is pre-start energized marked as 313 in Figure 22 the figure. Calculate the positive sequence amplitude current I m0 (Pre-start). Then, during operation 362, at time T1, both the main winding and the auxiliary winding are powered to start under the load conditions of the household clothes dryer. The motor operates in a two-phase mode, and calculate I m0 (Starting) as a reference to detect the overspeed point, and then the real-time positive sequence amplitude current I m0 (Open) starts to decrease and is calculated to detect the overspeed point. At time T2, the speed reaches the overspeed point ( Figure 22in 317), and the auxiliary winding is disconnected from the circuit system. Then, in 363, the motor enters the single-phase operation mode and accelerates the rotor speed to the rated speed during normal dryer operation, and the positive-sequence amplitude current decreases to the rated operating current. At time T3, a square-wave pulse torque is applied, and the motor begins to be forced to reduce its speed ( Figure 23B of 344), while the positive-sequence amplitude current in single-phase operation increases until two conditions for overload detection are met at time T4. The closing speed point is detected by 364 and 370. Then, in 365 and 371, the electronic switch assembly detects that the speed has dropped below the closing speed point and reconnects the power supply to the auxiliary winding to restart the motor again. When the speed exceeds the overspeed point speed, the auxiliary winding is disconnected again. This exemplary operating condition where the speed rises and falls between 65% and 70% of the synchronous speed can be repeated several times until the large load torque disappears inside the rotating drum. Then, at time T5, the overload torque disappears, and the motor speed accelerates to the rated speed and returns to normal single-phase operation mode to operate the household dryer.

[0263] Figure 24C shows the relationship between the positive-sequence amplitude voltage characteristic and time during start-up and overload operation in order to maintain the normal operating speed under the load curve simulating the operation of a household dryer. The positive-sequence amplitude voltage and the positive-sequence amplitude current are used for the calculation of the positive-sequence amplitude impedance.

[0264] Therefore, the electronic switch assembly control algorithm effectively detects the motor start-up speed and the overload speed reduction in real time to operate the household dryer. To verify its robustness, Table 1 gives examples of the test and simulation results of some control variables for operating the split-phase induction motor of the household dryer under different voltage operating conditions.

[0265] Table 1: Test and simulation results of the effectiveness and robustness of the electronic switch control algorithm under different voltage operating conditions.

[0266]

[0267] When the power supply voltage varies significantly in the range from 100VAC to 140VAC, even though all positive-sequence amplitude currents change accordingly, the control coefficients C im (Crossover) and C im (Closing) and the positive-sequence impedance Z m0 (Closing) all remain stable and relatively constant, namely 0.65, 0.77, and 11.6 ohms respectively. Therefore, the electronic starting switch assembly and control algorithm described in the present disclosure prove the effectiveness and robustness of operating the household dryer.

[0268] Directional terms such as "vertical", "horizontal", "top", "bottom", "upper", "lower", "inner", "inward", "outer", and "outward" are used to assist in describing the present invention based on the orientation of the embodiments shown in the figures. The use of directional terms should not be construed as limiting the present invention to any particular direction.

[0269] The foregoing description is of the current embodiments of the present invention. Various changes and variations can be made without departing from the spirit and broader aspects of the present invention as defined by the appended claims, which will be interpreted in accordance with the principles of patent law including the doctrine of equivalents. The present disclosure is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the present invention or as limiting the scope of the claims to the specific elements shown or described in connection with these embodiments. By way of example and not limitation, any single element of the described invention can be replaced by an alternative element that provides substantially similar functionality or otherwise provides adequate operation. This includes, for example, alternative elements that are currently known (e.g., those that may currently be known to those skilled in the art), as well as alternative elements that may be developed in the future (e.g., those that may be recognized as alternatives by those skilled in the art at the time of development). Additionally, the disclosed embodiments include a plurality of features that are consistently described and can cooperate to provide benefits. The present invention is not limited to those embodiments that include all of these features or provide all of the stated benefits, unless expressly set forth in the issued claims. For example, any reference in a claim element to the singular using a quantifierless modifier, "the", or "said" should not be construed as limiting the element to the singular form.

Claims

1. An electronic starter switch assembly for controlling the operation of a clothes dryer of a split-phase induction motor, wherein the split-phase induction motor has a main winding and an auxiliary winding embedded in a stator distribution slot to enable the rotor to rotate, and the electronic starter switch assembly comprises: The MCU is programmed to execute a control method for operating a clothes dryer, the control method comprising controlling a split-phase induction motor of the clothes dryer; The memory is configured to store various parameters of the overspeed condition; A sensing circuit system is used to sense or detect the characteristics of the split-phase induction motor; The power electronic switching circuit is configured to connect or disconnect the auxiliary winding and the heater element of the split-phase induction motor to or from the corresponding power source; Wherein, the MCU is configured as follows: Read the overspeed coefficient from the memory; Connecting the motor auxiliary winding to the motor power supply so that the motor rotor speed begins to accelerate during the starting operation; The main winding current and the auxiliary winding current are sampled in real time to generate real-time sampling values ​​of the main winding current and the auxiliary winding current; Based on the main winding current and the auxiliary winding current, the starting positive sequence amplitude current just reaching stability is calculated; Calculating and determining an overspeed condition current value based on the stable starting positive sequence amplitude current and the overspeed coefficient and storing the overspeed condition current in a memory; When the auxiliary winding is connected to the motor power supply during the starting time period, the starting real-time positive sequence amplitude current is detected based on the real-time sampling of the main winding current and the auxiliary winding current; Determine whether the starting real-time positive sequence amplitude current meets the resulting overspeed condition, and take actions to 1) disconnect the motor auxiliary winding from the motor power supply; and 2) connect the heater element to the power supply of the heater element.

2. The electronic starter switch assembly according to claim 1, wherein: The MCU is programmed to use a moving sampling window filtering method to calculate the average value of the starting real-time positive sequence amplitude current.

3. The electronic starter switch assembly according to claim 2, wherein: The MCU is programmed to determine whether the starting real-time positive-sequence amplitude current reaches the overspeed condition by comparing the starting real-time positive-sequence amplitude current with the overspeed condition current value, wherein the overspeed condition is a current value at an overspeed speed point and is determined by the starting positive-sequence amplitude current average value and the overspeed coefficient just after stability is achieved at the starting instant.

4. The electronic starter switch assembly according to claim 1, wherein: The MCU is programmed to detect the real-time positive sequence amplitude current at start-up, with the following details: Define the main winding voltage and main winding current to be expressed in phase A coordinates; The auxiliary winding voltage and the auxiliary winding current are defined to be expressed in the B-phase coordinate, wherein the positive direction of the B-phase coordinate coincides with the opposite direction of the positive direction of the auxiliary winding centerline axis, that is, the B-phase coordinate axis lags the positive direction of the auxiliary winding axis by 180 electrical degrees; Convert the main winding current into the A-phase current in the A-phase coordinate system; Convert the auxiliary winding current into the B-phase current in the B-phase coordinate system; Applying Park transformation to the A-phase current and the B-phase current to convert from a static AB coordinate system to a synchronous speed coordinate system dq axis to obtain a dq current, wherein the dq current includes one or more DC positive sequence current components and one or more negative sequence current components, wherein the one or more negative sequence current components are represented as second harmonic AC components; The negative sequence current component can be removed by filtering the dq current, thereby obtaining one or more DC positive sequence current components (i d0 ,i q0 );as well as From the DC positive sequence current component (i d0 ,i q0 ) to obtain the real-time positive sequence amplitude current at starting.

5. The electronic starter switch assembly according to claim 1, wherein: The MCU is programmed to continue single-phase operation until the dryer operation is completed or an overload condition is detected.

6. The electronic starting switch assembly of claim 1 further comprising a memory configured to store one or more parameters associated with an overload condition at which the rotor speed will drop below the speed of the closing speed point, wherein the MCU is programmed to detect whether an overload condition has occurred.

7. The electronic starter switch assembly according to claim 6, wherein: The MCU is programmed to: The MCU calculates the pre-start positive sequence amplitude current before connecting the auxiliary winding to the power supply voltage to accelerate the rotor speed at the start of the starting operation; Read the preset speed closing coefficient from the memory; Determine the value of the closing speed point of the positive sequence amplitude current during operation based on the calculated positive sequence amplitude current before starting and the read speed closing coefficient, and store the calculated closing speed point operating positive sequence amplitude current in a memory; During the single-phase operation period of the main winding when the auxiliary winding is disconnected from the power supply, the positive sequence amplitude current of the operation is detected; A determination is made as to whether an overload condition has occurred based on a comparison of the operating positive sequence magnitude current with the operating positive sequence magnitude current of the stored closing speed point. Once an overload condition has occurred, the following response actions are taken: 1) disconnecting the heater element from the power supply to the heater element; and 2) reconnecting the auxiliary winding to the power supply to increase the motor rotor speed.

8. The electronic starter switch assembly according to claim 7, wherein: The MCU is programmed to detect the positive sequence magnitude current during operation: Define the main winding voltage and main winding current to be expressed in the A phase coordinate; The auxiliary winding voltage and the auxiliary winding current are defined to be expressed in the B-phase coordinate, wherein the positive direction of the B-phase coordinate is aligned in the opposite direction of the positive direction of the auxiliary winding, that is, the B-phase b-axis lags the positive direction of the auxiliary winding central axis by 180 electrical degrees; Converting the main winding current into the A-phase current in the A-phase coordinate system; Converting the auxiliary winding current into a B-phase current in the B-phase coordinate system; Applying Park transformation to the A-phase current and the B-phase current to convert from a static AB coordinate system to a synchronous speed coordinate system dq axis to obtain a dq current, wherein the dq current includes one or more DC positive sequence current components and one or more negative sequence current components, wherein the one or more negative sequence current components are second harmonic AC components; The dq current is filtered to remove the negative sequence current component, thereby obtaining the DC positive sequence current component (i d0 ,i q0 );as well as From the DC positive sequence current component (i d0 ,i q0 ) to obtain the operating positive sequence amplitude current.

9. The electronic starter switch assembly according to claim 7, wherein: The MCU is programmed to: Read the positive sequence amplitude impedance closing point value; Calculate the operating positive sequence magnitude impedance; and Compare the operating positive sequence amplitude impedance with the positive sequence amplitude impedance closing point value to confirm whether an overload condition occurs.

10. The electronic start switch assembly according to claim 6, wherein the MCU is programmed to: Reading a predetermined closed positive sequence impedance from a memory; detecting the operating positive sequence amplitude impedance during an operating period when the auxiliary winding is disconnected from the power supply; Determining that the operating positive sequence amplitude impedance is equal to a predetermined closed positive sequence amplitude impedance, once this occurs, 1) disconnecting the heater element from a power source to the heater element; 2) Reconnecting the auxiliary winding to the power supply of the auxiliary winding to increase the motor rotor speed.

11. The electronic starter switch assembly according to claim 10, wherein: The MCU is programmed to detect the positive sequence magnitude impedance of the operation: Define the main winding voltage and main winding current to be expressed in phase A coordinates; The auxiliary winding voltage and the auxiliary winding current are defined to be expressed in the B-phase coordinate, wherein the positive direction of the B-phase coordinate is aligned in the opposite direction of the positive direction of the auxiliary winding, that is, the B-phase coordinate axis lags the positive direction of the auxiliary winding central axis by 180 electrical degrees; Convert the main winding current into the A-phase current in the A-phase coordinate system; Convert the auxiliary winding current into the B-phase current in the B-phase coordinate system; Convert the main winding voltage into the A phase voltage in the A phase coordinate system; Convert the auxiliary winding voltage into the B-phase voltage in the B-phase coordinate system; Applying Park transformation to the A-phase voltage and the B-phase voltage, converting from the static AB coordinate system to the dq axis of the synchronous speed coordinate system to obtain a dq voltage, wherein the dq voltage includes one or more DC positive sequence voltage components and one or more negative sequence voltage components, wherein the negative sequence voltage component is a second harmonic AC component; Applying Park transformation to the A-phase current and the B-phase current to convert from a static AB coordinate system to a synchronous speed coordinate system dq axis to obtain a dq current, wherein the dq current includes one or more DC positive sequence current components and one or more negative sequence current components, wherein the one or more negative sequence current components are second harmonic AC components; The dq voltage is filtered to remove the negative sequence voltage component, thereby obtaining one or more DC positive sequence voltage components (V d0 , V q0 ); The dq current is filtered to remove the negative sequence current component, thereby obtaining one or more DC positive sequence current components (i d0 ,i q0 ); From the one or more DC current components (I d0 , I q0 ) to obtain the operating positive sequence amplitude current (I m0 ); From the one or more DC voltage components (V d0 , V q0 ) to obtain the operating positive sequence amplitude voltage (V m0 );as well as The operating positive sequence amplitude impedance (Z) is obtained according to the operating positive sequence amplitude voltage and the operating positive sequence amplitude current. m0 ).

12. The electronic starter switch assembly of claim 1, comprising a housing configured to receive the PCB and containing a heat sink.

13. The electronic starter switch assembly of claim 12, wherein: The radiator includes a fin structure parallel to the motor axis to improve the airflow generated by the fan on the rotor end ring and thus improve the heat dissipation conditions.

14. The electronic starter switch assembly of claim 13, wherein: The size and shape of the shell are consistent with the end component structure of the split-phase induction motor, and side cooling fins can be added to the radiator to increase the effective heat dissipation surface area of ​​the airflow.

15. The electronic start switch assembly of claim 12, comprising an inner housing that allows the PCB to be mounted within the housing and allows for filling with protective material to protect the electronic components from damage by the working environment.

16. A method for controlling the operation of a clothes dryer having a split-phase induction motor, the split-phase induction motor having a memory, a controller, one or more power supplies, a main winding, an auxiliary winding, a heater, and an electronic start switch assembly, the method comprising: Read the overspeed coefficient from the memory; connecting the auxiliary winding to the power source so that the rotor speed begins to increase during a starting operation period; Detecting the main winding current and the auxiliary winding current during the starting operation period; Calculating a starting positive sequence amplitude current that has just reached stability based on the main winding current and the auxiliary winding current sensed at the beginning of the starting operation period; Calculating an overspeed condition based on the obtained stable starting positive sequence amplitude current and the overspeed coefficient and storing the overspeed condition in a memory; Calculating and determining a real-time starting positive sequence amplitude current based on the main winding current and the auxiliary winding current sensed during the starting operation period; Determine whether the real-time starting positive sequence amplitude current meets the overspeed condition, and respond once it occurs by 1) disconnecting the auxiliary winding from the power supply; 2) connecting the heater element to the power supply of the heater.

17. The method for controlling the operation of a clothes dryer according to claim 16, wherein: Determining the real-time starting positive sequence amplitude current includes calculating the real-time starting positive sequence amplitude current average value by applying a moving window sampling filtering method to the main winding current and the auxiliary winding current during the starting operation period.

18. The method for controlling the operation of a clothes dryer according to claim 17, wherein determining whether the real-time starting positive sequence amplitude current satisfies the overspeed condition comprises comparing the real-time starting positive sequence amplitude current average value with the overspeed condition current value. The overspeed condition calculation is determined by multiplying the starting positive sequence amplitude current that has just stabilized at the starting moment by the overspeed point positive sequence amplitude current value and the overspeed coefficient.

19. The method for controlling the operation of a clothes dryer according to claim 16, comprising detecting an overload condition, in which case the rotor speed will drop below the closing speed point speed.

20. The method for controlling the operation of a clothes dryer according to claim 19, comprising: Before connecting the auxiliary winding to the power supply so that the rotor speed begins to increase during a starting operation period, calculating a positive sequence amplitude current before starting; Read the closure coefficient from memory; Calculating and determining the positive sequence amplitude current value of the closing speed point of the running positive sequence amplitude current based on the positive sequence amplitude current before starting and the closing coefficient and storing it in a memory; When the auxiliary winding is disconnected from the power supply, that is, the main winding is in single-phase operation, the positive sequence amplitude current is detected; determining whether an overload condition has occurred based on a comparison of the operating positive sequence amplitude current with a value of the operating positive sequence amplitude current closing speed point, and responding if an overload condition has occurred by 1) disconnecting the heater element from its power source; and 2) reconnecting the auxiliary winding to the power supply of the auxiliary winding so that the motor rotor speed is increased.

21. The method for controlling the operation of a clothes dryer according to claim 20, comprising: Read the value of the positive sequence amplitude impedance closing point; Determine the operating forward magnitude impedance; as well as Based on a comparison between the operating positive-sequence amplitude impedance and the value of the positive-sequence amplitude impedance closure point, it is determined whether an overload condition exists.

22. The method for controlling the operation of a clothes dryer according to claim 19, comprising: reading a predetermined closed positive sequence impedance from a memory; detecting an operating positive sequence amplitude impedance during an operating period when the auxiliary winding is disconnected from the power supply; as well as determining that the operating positive sequence amplitude impedance reaches the predetermined closed positive sequence amplitude impedance, and in response thereto, 1) disconnecting the heater element from a power source to the heater element; and 2) reconnecting the auxiliary winding to the power source to increase the motor rotor speed.

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