Single-phase asynchronous motor control method based on starting phase enhancement

Abstract

The application discloses a single-phase asynchronous motor control method based on starting phase enhancement, relates to the asynchronous motor control field, and first, adopts an MCU as a control center and cooperates with a first zero-crossing optical coupler and a second zero-crossing optical coupler. Secondly, a phase-shifting element in a starting branch is defined as a phase enhancement component, and it is clear that the phase-shifting element can make the starting current phase ahead of the running current by a predetermined range which can be designed. Finally, through the precise cooperation of electronic devices, the traditional passive phase-shifting starting is upgraded to active and optimized phase enhancement control, and the efficient, stable and reliable motor starting process is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of asynchronous motor control, and more particularly, to a single-phase asynchronous motor control method based on starting phase enhancement. BACKGROUND

[0002] Single-phase asynchronous motors are widely used in industrial production and household appliances, such as compressors, fans, water pumps, and other equipment, due to their simple structure, low cost, and reliable operation. However, single-phase asynchronous motors cannot generate starting torque on their own and need to rely on auxiliary windings, i.e., starting windings and phase-shifting elements, to generate a rotating magnetic field and thus achieve starting. Therefore, how to effectively improve the starting performance of the motor, especially the starting torque, is a technical problem that continues to be concerned in the field of motor control. Developing a control scheme that can enhance the starting phase is of great significance for improving the instantaneous capability and reliability of motor starting and coping with heavy load starting scenarios.

[0003] In existing technologies, traditional single-phase asynchronous motor starters, such as weight-type or centrifugal switch-type starters, usually control the on-off of the starting windings in a mechanical manner. More commonly, a fixed starting capacitor is connected in series with the starting windings, and the phase of the current in the starting windings is made to lead the phase of the current in the running windings by about 90° through the physical characteristics of the capacitor, so as to form the rotating magnetic field required for starting. However, such traditional starters have obvious defects: first, the phase shift angle is fixed and completely dependent on the capacitance value of the capacitor, and cannot be dynamically adjusted according to the actual load or power grid conditions to achieve the best starting effect, i.e., the starting phase cannot be actively enhanced. Second, the on-off timing of mechanical switches or relays is often random and may be closed at any phase point of the alternating voltage, which can cause a large current surge and an unstable initial magnetic field, affecting the smoothness and reliability of starting, and even may interfere with the power grid.

[0004] Therefore, the existing technical solutions have limitations in accurately controlling the starting phase and optimizing the starting torque, making it difficult to meet higher performance requirements. SUMMARY

[0005] In view of the limitations in the prior art, according to an aspect of the present application, a single-phase asynchronous motor control method based on starting phase enhancement is provided, which comprises the following steps: in response to receiving a starting instruction, an MCU simultaneously sends a conduction signal to a first zero-crossing optocoupler for controlling a main thyristor and a second zero-crossing optocoupler for controlling an auxiliary thyristor; when an alternating voltage crosses zero, the first zero-crossing optocoupler and the second zero-crossing optocoupler are activated to simultaneously trigger the main thyristor and the auxiliary thyristor to conduct; after the main thyristor and the auxiliary thyristor are conducted, a current simultaneously flows through a running branch composed of a running winding and a starting branch composed of a phase enhancement component and a starting winding, wherein the phase enhancement component causes the current flowing through the starting branch to be ahead of the current flowing through the running branch by a predetermined range.

[0006] In the single-phase asynchronous motor control method based on starting phase enhancement described above, the predetermined range is 30° to 150°.

[0007] In the single-phase asynchronous motor control method based on starting phase enhancement described above, the phase enhancement component causes the current flowing through the starting branch to be ahead of the current flowing through the running branch by 90°.

[0008] In the single-phase asynchronous motor control method based on starting phase enhancement described above, the phase enhancement component is a thermistor.

[0009] In the single-phase asynchronous motor control method based on starting phase enhancement described above, one end of the running winding is electrically connected to the main thyristor, the other end of the running winding is electrically connected to a zero line of an alternating power source, one end of the starting winding is electrically connected to the auxiliary thyristor, and the other end of the starting winding is electrically connected to the zero line of the alternating power source.

[0010] In the single-phase asynchronous motor control method based on starting phase enhancement described above, the method further comprises the following steps: after detecting that the motor has reached a normal running speed, the control unit stops sending the conduction signal to the second zero-crossing optocoupler for controlling the auxiliary thyristor; after the second zero-crossing optocoupler does not receive the conduction signal, the auxiliary thyristor remains conducted until the auxiliary thyristor is automatically turned off when the current next crosses zero.

[0011] In the single-phase asynchronous motor control method based on starting phase enhancement described above, the method further comprises the following step: when the auxiliary thyristor is automatically turned off, the main thyristor remains conducted.

[0012] Compared with the prior art, the single-phase asynchronous motor control method based on starting phase enhancement provided by the application first realizes the synchronous triggering of the main and auxiliary thyristors at the zero-crossing point of the alternating voltage by using an MCU as a control center and cooperating with a first zero-crossing optical coupler and a second zero-crossing optical coupler. This zero-voltage opening strategy solves the problems of huge current impact and unstable initial magnetic field caused by the random closing time of the traditional mechanical switch, and provides a smooth and clean starting electrical environment for the motor. Secondly, the phase-shifting element in the starting branch is defined as a phase enhancement component, and it is clear that it can make the starting current phase advance the operating current by a predetermined range that can be designed. This overcomes the limitation that the traditional fixed capacitor cannot actively optimize the starting performance, and by actively designing the phase difference to synthesize the most ideal rotating magnetic field, the starting torque is significantly enhanced. Finally, through the precise cooperation of electronic devices, the traditional passive phase-shifting starting is upgraded to active and optimized phase-enhancement control, and the efficient, smooth and reliable motor starting process is realized. BRIEF DESCRIPTION OF DRAWINGS

[0013] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description of embodiments of the present application, taken in conjunction with the accompanying drawings. The drawings provided in the present application are used to provide further understanding of the embodiments of the present application, and constitute a part of the specification, and are used to explain the present application together with the embodiments of the present application, and do not constitute a limitation of the present application. In the drawings, the same reference numerals generally represent the same components or steps.

[0014] Figure 1 A flowchart of the single-phase asynchronous motor control method based on starting phase enhancement according to the embodiments of the present application.

[0015] Figure 2 A basic principle diagram of the single-phase asynchronous motor control method based on starting phase enhancement.

[0016] Figure 3 A current waveform diagram of the running winding and the starting winding in the single-phase asynchronous motor control method based on starting phase enhancement.

[0017] Figure 4 A formation process diagram of the rotating magnetic field in the single-phase asynchronous motor control method based on starting phase enhancement.

[0018] Figure 5 A flowchart of other implementation steps in the single-phase asynchronous motor control method based on starting phase enhancement according to the embodiments of the present application. DETAILED DESCRIPTION

[0019] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0020] In view of the shortcomings of the aforementioned methods in practical applications, this application proposes a single-phase asynchronous motor control method based on start-up phase enhancement. Figure 1 This is a flowchart of a single-phase asynchronous motor control method based on start-up phase enhancement according to an embodiment of this application. Figure 1 As shown, the single-phase asynchronous motor control method based on start-up phase enhancement according to an embodiment of this application includes the following steps: S1, in response to receiving a start command, the MCU simultaneously sends a turn-on signal to a first zero-crossing optocoupler and a second zero-crossing optocoupler controlling the main thyristor and the auxiliary thyristor, wherein the first zero-crossing optocoupler is connected in series with the main thyristor and the second zero-crossing optocoupler is connected in series with the auxiliary thyristor; S2, when the AC voltage passes through zero, the first zero-crossing optocoupler and the second zero-crossing optocoupler are activated to simultaneously trigger the main thyristor and the auxiliary thyristor to turn on; S3, after the main thyristor and the auxiliary thyristor are turned on, current simultaneously flows through the running branch composed of the running winding and the start-up branch composed of the phase enhancement element and the start-up winding, wherein the phase enhancement element causes the phase of the current flowing through the start-up branch to lead the phase of the current flowing through the running branch by a predetermined range.

[0021] To achieve the aforementioned control method, each component plays an indispensable role through precise coordination. It can be understood that the MCU is the core of the entire control method; as the control unit, its main function is to issue start and stop commands. In response to the start request, the MCU sends a high-level or low-level conduction signal to the subsequent control circuits, thereby determining the timing of the switch between motor start and running states.

[0022] The main and auxiliary thyristors are power electronic switching devices used to control the on / off state of the running and starting circuits, respectively. The main thyristor acts as the main switch, connected in series on the live wire of the AC power supply, responsible for controlling the overall power supply to the motor. The auxiliary thyristor serves as the switch for the starting circuit, connected in series within the starting circuit, used to connect the starting winding during motor startup and disconnect it after startup is complete. Notably, thyristors can carry large currents and have a self-locking characteristic once triggered, automatically turning off only when the current crosses zero. This characteristic provides a prerequisite for precise control.

[0023] The first zero-crossing optocoupler and the second zero-crossing optocoupler are key components for precise timing control, and they are the isolation and synchronization bridge between the weak electrical control signal of MCU and the strong electrical drive of thyristor. The zero-crossing detection circuit integrated in the zero-crossing optocoupler ensures that the thyristor connected to it will only be triggered at the moment when the AC power voltage crosses zero. Therefore, even if the MCU sends a signal to turn on the thyristor in advance, the zero-crossing optocoupler will wait until the next voltage zero-crossing point before executing the triggering action. In this way, it avoids the huge current impact and electromagnetic interference caused by turning on the circuit at any arbitrary time such as voltage peak, and creates a stable and clean electrical environment for motor starting.

[0024] The running winding and the starting winding are the stator windings of the single-phase asynchronous motor, and they are usually distributed at a spatial angle of 90 degrees. The running winding is the winding that works continuously when the motor is in normal operation, while the starting winding is only energized during the starting phase and cooperates with the running winding to generate a rotating magnetic field.

[0025] The phase enhancement component is the key to achieving a phase difference. It is connected in series in the starting branch, and its capacitive reactance characteristic allows the current flowing through the starting branch to lead the current flowing through the running branch. Through precise zero-crossing synchronization triggering and the phase-shifting effect of the component, an ideal current phase difference of approximately 90 degrees can be established in the two windings, thereby maximizing the starting torque and effectively enhancing the starting ability of the motor. These components work together to achieve enhanced control of the starting phase of the single-phase asynchronous motor.

[0026] That is, the entire control process begins with the MCU responding to the starting instruction. As the control center, the MCU immediately sends a signal to the first and second zero-crossing optocouplers that control the main and auxiliary thyristors, respectively. The zero-crossing optocoupler, as a precise synchronization trigger, does not act immediately but waits for the next zero-crossing moment of the AC power voltage. At the voltage zero-crossing point, both zero-crossing optocouplers are activated, triggering the main and auxiliary thyristors to turn on simultaneously. This zero-crossing synchronization triggering strategy allows the current to flow smoothly and without impact into the running winding and the starting winding. At this time, the phase enhancement component connected in series in the starting winding branch plays a role, making the current phase of the starting winding lead the current phase of the running winding by a predetermined angle, thereby forming an efficient, smooth, and powerful rotating magnetic field in the two spatially orthogonal windings, significantly enhancing the starting torque of the motor. When the MCU detects that the motor has reached normal speed, it stops sending signals to the second zero-crossing optocoupler, and the auxiliary thyristor will automatically turn off at the next current zero-crossing point, leaving only the main thyristor to remain on, allowing the motor to smoothly switch to the running state.

[0027] In detail, in step S1, in response to receiving a starting instruction, the MCU simultaneously sends a conduction signal to a first zero-crossing optocoupler in series with the main thyristor and a second zero-crossing optocoupler in series with the auxiliary thyristor. It should be understood that the MCU as the control center simultaneously sends, which ensures that the control intentions for the running branch and the starting branch are synchronized, aiming to make the two branches ready at the same time. However, the actual conduction time is not directly determined by the MCU, but is determined by the zero-crossing optocoupler. In this way, the fundamental pain points of the traditional starter in the background art, which causes a huge current impact and an unstable initial magnetic field due to closing at an arbitrary phase point of the alternating voltage, are solved. By the zero-crossing optocoupler, the conduction time can be forcibly locked at the zero-crossing point of the alternating voltage, thereby realizing zero-voltage opening. This not only greatly suppresses the inrush current, effectively protecting the power components and the power grid, but more importantly, it establishes an absolutely synchronized and clean and stable starting reference point for the two windings, so that the phase difference generated by the phase enhancement component in the subsequent process can be accurately established on a pure and undisturbed reference, thereby truly achieving the ultimate goal of starting phase enhancement.

[0028] A specific implementation process of step S1 is as follows: the MCU has a firmware program inside which pre-sets a response mechanism for the motor starting logic. Two general-purpose input / output (GPIO) pins of the MCU, for example, GPIO_A and GPIO_B, are configured in push-pull output mode. The GPIO_A pin is electrically connected to the input end anode of the first zero-crossing optocoupler through a current-limiting resistor, and the GPIO_B pin is also electrically connected to the input end anode of the second zero-crossing optocoupler through a current-limiting resistor. The input end cathodes of the two zero-crossing optocouplers are commonly grounded. In the standby state, the MCU sets both GPIO_A and GPIO_B pins to low, i.e., logic 0, through the internal program, at which time the pin output voltage is close to 0V, and the light-emitting diode inside the zero-crossing optocoupler cannot work.

[0029] When a specified input pin of the MCU, for example, a pin configured as an external interrupt, receives a starting instruction from the outside, the instruction can be a level jump generated by closing a physical switch or a digital signal sent by other logic circuits. The hardware interrupt of the MCU is triggered, and the processor immediately suspends the current task and jumps to the pre-written interrupt service program (ISR) to execute.

[0030] In this interrupt service routine, the core instruction sequence is designed to change the output states of GPIO_A and GPIO_B at almost the same time. In implementation, this can be efficiently done by a direct write operation to the port register, which changes the levels of multiple pins at the same time in one machine cycle. The MCU executes one instruction to set the corresponding bits in the port data registers that control GPIO_A and GPIO_B to 1 at the same time. After the execution of this write operation instruction, the output voltages of GPIO_A and GPIO_B jump from low to high, for example, 3.3V or 5V, at almost the same time. This high voltage is applied to the two current-limiting resistors, generating a driving current that flows through the light-emitting diodes inside the first and second zero-crossing optocouplers at the same time. The light-emitting diodes are lit, emitting light signals. At this point, the action of the MCU sending a trigger signal to the two zero-crossing optocouplers at the same time is completed. This trigger signal physically manifests as a level transition from low to high on the two specific pins of the MCU that occurs synchronously, which marks the formal start of the motor starting program and prepares for the subsequent zero-crossing optocouplers to trigger the thyristors at the precise time. The MCU will continue to output this high-level signal until the motor starting is completed.

[0031] In step S2, when the AC voltage passes through zero, the first zero-crossing optocoupler and the second zero-crossing optocoupler are activated to trigger the main thyristor and the auxiliary thyristor to conduct at the same time. Accordingly, this step realizes zero-voltage turn-on by forcibly requiring that the conduction is allowed only when the AC voltage crosses zero. On the one hand, this greatly protects power devices such as thyristors from large current surges, prolongs the life of the device, and reduces electromagnetic interference to the power grid; on the other hand, it ensures that the running winding and the starting winding start working on the same, undisturbed electrical reference. Only on such an ideal synchronous starting point, the current phase difference established by the phase enhancement components can be accurate and stable, ensuring that the resulting rotating magnetic field is efficient and smooth from the first cycle, ultimately achieving effective enhancement of the starting torque.

[0032] A specific implementation process of step S2 is as follows: the MCU has sent a continuous conduction signal to the input end (internal light-emitting diode) of the two zero-crossing optocouplers, that is, a driving voltage is applied. At this time, the light-emitting diodes in the two optocouplers are in a continuous light-emitting state, but the output end (internal photoelectric bidirectional triode) of the optocoupler is not immediately turned on, and the entire circuit is in a standby state. The zero-crossing optocoupler integrates a precise zero-crossing detection circuit, which continuously monitors the AC power voltage connected to the output end of the optocoupler. Specifically, the detection circuit monitors the voltage applied between the two pins of the optocoupler output end, which is actually the instantaneous AC voltage that the main and auxiliary thyristors bear in the off state. When the AC power voltage is at the peak or other non-zero position of the sine waveform, the zero-crossing detection circuit determines that the absolute value of the current voltage is higher than the internal set threshold voltage (for example, a few volts). During this period, even if the internal light-emitting diode is emitting light, the detection circuit will actively inhibit the triggering of the photoelectric bidirectional triode, keeping it in the high resistance state of the off state.

[0033] With the change of the AC voltage waveform, as the voltage value gradually approaches zero, the absolute value of the voltage monitored by the zero-crossing detection circuit will decrease. At the moment when the AC voltage precisely crosses zero, the absolute value of the voltage will be lower than the internal threshold of the zero-crossing detection circuit. At this time, the inhibition of the detection circuit is removed, and it will immediately allow the photons emitted by the light-emitting diode to deactivate the gate of the photoelectric bidirectional triode. Since the MCU sends signals to the two zero-crossing optocouplers at the same time, the light-emitting diodes in the two optocouplers emit light synchronously, so at the same time when the voltage crosses zero, the photoelectric bidirectional triodes in the two optocouplers will be activated and turned on almost simultaneously.

[0034] Once the output end of the zero-crossing optocoupler is turned on, it forms a low-resistance path, providing a trigger current between the control gate and the main electrode of the main and auxiliary thyristors connected to it. This trigger current causes the main and auxiliary thyristors to transition from the off state to the conductive self-locking state. Since the two zero-crossing optocouplers are activated synchronously at the voltage zero-crossing point, they also provide trigger current to the main and auxiliary thyristors almost simultaneously, thereby achieving the synchronous conduction of the two thyristors at the AC voltage zero-crossing point. At this point, the entire activation and triggering process is complete, and the main and auxiliary windings of the motor are smoothly connected to the circuit under the most ideal electrical conditions.

[0035] In step S3, after the main and auxiliary thyristors are turned on, current flows simultaneously through the operating branch composed of the running winding and the starting branch composed of the phase enhancement device and the starting winding. The phase enhancement device causes the phase of the current flowing through the starting branch to lead the phase of the current flowing through the operating branch by a predetermined range. It should be understood that after the main and auxiliary thyristors are synchronously turned on at the voltage zero-crossing point, the two parallel branches are simultaneously connected to the AC power supply. At this time, the operating branch mainly exhibits inductive behavior, and its current phase lags behind the voltage phase. In the starting branch, due to the presence of the phase enhancement device, its circuit characteristics are significantly altered. The core function of this device is to adjust the impedance characteristics of the starting branch, causing the phase of the current flowing through this branch to significantly lead the phase of the current flowing through the operating branch. It is these two currents, which lead in time and are orthogonal in space (determined by the physical distribution of the windings), that together synthesize an ideal rotating magnetic field in the motor stator. In other words, by actively controlling and cooperating with components, the startup phase difference is expanded from a fixed value in the traditional scheme to a pre-designable range, thereby enabling optimization according to different loads and performance requirements, ultimately achieving a fundamental enhancement of startup performance.

[0036] Step S3 is implemented as follows: Specifically, in an exemplary embodiment of this application, Figure 2 This is a basic schematic diagram of a single-phase asynchronous motor control method based on start-up phase enhancement. Figure 2 As shown, one end of the running winding is electrically connected to the main thyristor, and the other end is electrically connected to the neutral line of the AC power supply. One end of the starting winding is electrically connected to the auxiliary thyristor, and the other end is electrically connected to the neutral line of the AC power supply. This connection method establishes a parallel topology between the running branch and the starting branch after the main thyristor, providing a basis for synchronous current distribution and phase difference establishment. Since the main and auxiliary thyristors were synchronously triggered to conduct at the precise moment of AC voltage zero crossing, they are both in a low-impedance closed state. The AC power supply voltage is therefore applied simultaneously to both the running branch and the starting branch, and current is then established and flows simultaneously in both branches. In the running branch, the current flows only through the running winding, which has significant inductive characteristics, so its current phase naturally lags behind the power supply voltage. Meanwhile, in the starting branch, the current passes through a key phase enhancement device before flowing to the starting winding. The selection and configuration of this device are the core of achieving phase enhancement.

[0037] Specifically, in one exemplary embodiment of the present application, the phase enhancement component is a capacitor, a thermistor or an inductor. When a capacitor is selected, its capacitive reactance characteristic makes the impedance of the entire starting branch capacitive, thereby making the current phase of the branch lead the supply voltage; when a thermistor (particularly a PTC with a positive temperature coefficient) is selected, its low resistance state at the starting moment can adjust the phase, and as the temperature rises due to current flow, the resistance increases sharply, which can also automatically disconnect the starting branch; when an inductor is selected, by matching with the inductance of the starting winding itself, a specific phase adjustment can also be achieved.

[0038] Preferably, in the technical solution of the present application, the phase enhancement component is a thermistor. It should be understood that the use of a thermistor (PTC) can fundamentally improve the safety and redundancy of the system. The thermistor, by virtue of its inherent physical characteristics, provides a passive, self-excited safety protection mechanism, i.e. after the motor is normally started, the continuous current will heat it up and instantly enter a high resistance state, thereby physically automatically disconnecting the branch of the starting winding. This means that even if the main control unit (MCU) or the auxiliary thyristor fails to issue or execute the shutdown instruction, the thermistor can still independently complete the task of cutting off, effectively preventing overheating and burning due to long-term power supply to the starting winding, and adding a hardware-level fault protection barrier that does not depend on software logic to the entire motor system.

[0039] At the same time, another significant advantage of selecting a thermistor is that it combines the functions of phase adjustment and self-shutdown switch, thereby simplifying system design and greatly enhancing control robustness. At the starting moment, its low resistance state participates in the construction of the starting phase; after starting, its high resistance state due to heating plays the role of a switch. This dual characteristic makes the control system less stringent in timing the disconnection of the starting winding, and even if there is an error in the delay judgment of the MCU, the self-protective thermistor can still ensure the safe disconnection of the circuit, which not only reduces the dependence on the accuracy of the control software, but also makes the entire system more adaptable to load changes and starting time fluctuations, ultimately forming a more robust and fault-tolerant control scheme.

[0040] In addition, the thermistor has a decisive advantage over the traditional starting capacitor. The starting capacitor, especially the large-capacity electrolytic capacitor, is sensitive to high temperature and vibration environment due to its internal electrolyte, and is prone to failure due to aging, drying or damage, which is a common weak point in the entire system. As a solid and stable solid-state ceramic semiconductor element, the thermistor has a longer service life, excellent anti-vibration performance and a wider operating temperature range, making the control module using a thermistor more durable and durable in harsh motor operating environments.

[0041] Moreover, the thermistor has excellent manufacturing friendliness, i.e. it can be directly integrated on a printed circuit board (PCB). Traditional start-up capacitors are usually bulky, irregular in shape, and need to be fixed on the device housing through a bracket, and then connected to the control board through long wires by manual work. This process not only increases the complexity of assembly and labor costs, but also introduces multiple potential failure points (such as wire breakage, loose joints). In contrast, the thermistor has a standardized package, fully compatible with modern electronic industry automated surface mount technology (SMT) or dual in-line package (DIP) production lines. This direct integration capability brings multiple benefits: first, it enables automation and high-speed production, greatly reducing manufacturing costs; second, it eliminates external components and wiring, allowing the entire control module to be designed much more compact and smaller than ever before to meet the extreme pursuit of space efficiency in modern appliances; finally, shorter circuit paths and more stable solder connections not only eliminate the risk of mechanical vibration, but also optimize the electrical performance of the circuit, reducing parasitic parameters and electromagnetic interference (EMI), thereby significantly improving the final product in terms of integration, reliability and performance.

[0042] By designing the parameters of the phase-enhancing component, it can be ensured that the phase of the current flowing through the start-up branch is ahead of the phase of the current flowing through the running branch by a predetermined range. Specifically, in an exemplary embodiment of the present application, the predetermined range is 30° to 150°. That is, by adjusting the parameters of the component, the predetermined range can be 30° to 150°. This range covers all phase relationships that can effectively generate starting torque, providing a wide design window to meet the needs of different motors. In a preferred embodiment, the circuit parameters are further optimized to obtain the maximum and most stable starting torque, i.e. a phase difference of 30° to 150° can improve the starting ability, and a phase difference of 90° is the most effective.

[0043] Specifically, the phase-enhancing component causes the phase of the current flowing through the start-up branch to be ahead of the phase of the current flowing through the running branch by 90°. The electrical characteristics and physical effects produced by this preferred scheme are explained in detail Figure 3 and Figure 4 . Figure 3 A current waveform diagram of one cycle of the running winding and the start-up winding in the single-phase asynchronous motor control method based on start-up phase enhancement is shown in FIG. 1. As shown in FIG. 1, the red line represents the current phase of the running winding (main winding), and the green line represents the current phase of the start-up winding (auxiliary winding). As can be seen from FIG. 1, the phase of the green line is significantly ahead of the phase of the red line, with a phase difference of approximately 90 degrees. It is this current with a phase difference in time that enables the motor to generate a rotating magnetic field. Figure 3 Figure 3

[0044] ​​Figure 4 A process diagram of the formation of the rotating magnetic field in the single-phase asynchronous motor control method based on starting phase enhancement is shown in FIG. 1. As shown in FIG. 1, the stator of the single-phase asynchronous motor has main windings (main winding A and main winding B) and auxiliary windings (auxiliary winding A and auxiliary winding B), which are orthogonally distributed in space. The rotor is affected by the rotating magnetic field formed after the stator is energized and rotates with the rotating magnetic field. Figure 4 Figure 3 As shown in waveform S1, at this time, the current of the main winding is 0, the current of the auxiliary winding is the largest, and the current direction is from the auxiliary winding A to the auxiliary winding B. At this time, an electromagnetic field is generated, so that the rotor rotates. Figure 4 Q1 to Q8 sequence in FIG. 1 corresponds to different time points (S1 to S8) in one current cycle in FIG. 2. At these different time sequences, due to the different current sizes and directions of the main winding and the auxiliary winding, the magnetic field direction (N-S pole direction in the figure) synthesized by them also continuously changes, thereby forming a smooth rotating magnetic field. Finally, the two currents that are orthogonal in time act on the windings that are orthogonal in space, thereby synthesizing the most ideal circular rotating magnetic field in the motor, providing strong and stable starting torque for the motor, and maximizing the starting performance. Figure 3

[0045] Specifically, in one of the example embodiments of the present application, Figure 5 A flowchart of other implementation steps in the single-phase asynchronous motor control method based on starting phase enhancement according to the embodiments of the present application is shown in FIG. 3. As shown in FIG. 3, Figure 5 ​​As shown, the single-phase asynchronous motor control method based on starting phase enhancement further comprises the following steps: Step 1, after detecting that the motor has reached the normal running speed, the control unit stops sending the conduction signal to the second zero-crossing optocoupler for controlling the auxiliary thyristor; Step 2, after the second zero-crossing optocoupler does not receive the conduction signal, the auxiliary thyristor remains conducting until the current next zero-crossing, at which time the auxiliary thyristor automatically turns off. It can be understood that the starting winding and the phase enhancement components connected in series thereof are used to generate a rotating magnetic field by cooperating with the running winding to provide a strong starting torque when the motor is at rest or at low speed. However, once the motor reaches its rated speed or approaches the synchronous speed, the cutting magnetic induction effect generated by the rotation of the rotor itself can already maintain its stable operation, and the assistance of the starting winding is no longer needed. If the starting winding is still powered during the normal operation of the motor, a series of negative effects will be caused: first, the starting winding is usually designed for short-time operation, and long-time power-on will generate excessive heat due to the continuous current flowing through, which can easily cause the winding to overheat, damage the insulation, or even burn out, seriously affecting the service life and safety of the motor. Second, the phase enhancement components (especially the capacitor) in the starting branch will also accelerate the aging or failure due to long-term operation. Third, the continuous operation of the starting winding will increase the total power consumption of the motor, reduce the operating efficiency, and cause unnecessary energy waste. Therefore, after the motor is successfully started, the starting branch needs to be disconnected from the circuit in a timely and reliable manner, and only the running winding needs to be kept working, which is a condition for ensuring that the motor can be operated safely, efficiently, and with a long service life.

[0046] A specific implementation process is as follows: after the control unit, i.e., the MCU, completes the starting program, it starts to continuously monitor the running state of the motor to determine whether it has reached the normal running speed. There are various methods for detecting that the motor has reached the normal running speed. For example, a timer delay judgment is used. Based on the prior knowledge of the characteristics of the motor and the load, a reasonable starting time can be set, for example, 500 milliseconds to 2 seconds. The MCU starts an internal timer at the same time as sending the starting signal, and when the timer counts to the preset value, it is determined that the motor has completed the starting. Another more accurate way is to detect the speed through sensors, such as installing a Hall sensor or an optical encoder on the motor shaft to directly measure the speed, or indirectly judging the speed by detecting the back electromotive force or current characteristics of the running winding. When the detected value reaches a certain percentage (for example, 75%) of the rated speed, it is determined that the starting is completed. Once the control unit detects that the motor has reached the normal running speed through any of the above methods, it immediately executes the preset switching program. The core action of the program is to stop sending the conduction signal to the second zero-crossing optocoupler for controlling the auxiliary thyristor. In physical implementation, the control unit re-sets the GPIO pin connected to the second zero-crossing optocoupler from high level to low level.

[0047] After the MCU withdraws the control signal, the light-emitting diode inside the second zero-crossing optocoupler is turned off. However, thanks to the self-holding characteristic of the thyristor, the already-on auxiliary thyristor does not immediately turn off, but remains on until the next time the alternating current flowing through the starting branch naturally crosses zero. At the moment of current zero-crossing, the auxiliary thyristor automatically turns off due to the disappearance of the current that maintains its on state and the absence of a trigger signal at the control gate, returning to the high-impedance state. This natural characteristic of the thyristor, which turns off when the current crosses zero, achieves a soft turn-off without electric arc or shock, smoothly disconnecting the starting branch from the circuit and avoiding the electric arc and voltage spikes that may occur when the circuit is forcibly disconnected at the current peak.

[0048] To ensure that the motor can continue to run, the switching process also includes a key coordinated action. Specifically, in another exemplary embodiment of the present application, the single-phase asynchronous motor control method based on starting phase enhancement further includes the step of: when the auxiliary thyristor automatically turns off, the main thyristor remains on. This is because the MCU continues to send a conduction signal to the first zero-crossing optocoupler while stopping sending a signal to the second zero-crossing optocoupler. Therefore, the main thyristor is always in a controlled on state, continuously providing power to the running winding. Eventually, with the natural turn-off of the auxiliary thyristor, the starting branch is safely and smoothly disconnected, while the running branch seamlessly continues to work, and the motor smoothly transitions from the starting phase to the stable running phase without disturbance.

[0049] In summary, the single-phase asynchronous motor control method based on starting phase enhancement based on the embodiments of the present application is illustrated, which uses an MCU as an intelligent core, combines zero-crossing optocouplers and power electronic devices such as thyristors, and realizes precise timing control of the single-phase asynchronous motor starting process. This scheme solves the technical problems in the background art that the traditional starter cannot actively enhance the starting phase, only passively relies on fixed capacitors for phase shifting, and the on-off timing randomly causes current shock. Specifically, first, by using an MCU as the control center and cooperating with the first and second zero-crossing optocouplers, the main and auxiliary thyristors are triggered to conduct synchronously at the zero-crossing point of the alternating voltage. This zero-voltage turn-on strategy solves the problem of large current shock and unstable initial magnetic field caused by random closing timing of traditional mechanical switches, providing a smooth and clean starting electrical environment for the motor. Second, the phase-shifting element in the starting branch is defined as a phase-enhancing component, and it is clear that it can make the starting current phase advance the running current by a predetermined range that can be designed. This overcomes the limitation of traditional fixed capacitors that cannot actively optimize the starting performance, and actively designs the phase difference to synthesize the most ideal rotating magnetic field, thereby significantly enhancing the starting torque. Finally, through the precise coordination of electronic devices, the traditional passive phase-shifting starting is upgraded to active and optimized phase-enhancing control, achieving efficient, smooth and reliable motor starting process.

[0050] Having described above several implementations of the disclosure, any of the above descriptions are exemplary and not exhaustive. And, although the present disclosure has been described above with the aid of specific embodiments, numerous modifications and changes will be apparent to those skilled in the art. Thus, the scope of the present disclosure should not be limited to the specific illustrative embodiments, but should be given the full scope defined by the appended claims and their equivalents. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

Claims

1. A single-phase asynchronous motor control method based on starting phase enhancement, characterized in that, The method comprises the following steps: In response to receiving the starting instruction, the MCU simultaneously sends a conduction signal to a first zero-crossing optocoupler and a second zero-crossing optocoupler for controlling the main thyristor and the auxiliary thyristor, the first zero-crossing optocoupler is connected in series with the main thyristor, and the second zero-crossing optocoupler is connected in series with the auxiliary thyristor; When the alternating voltage passes through zero, the first zero-crossing optocoupler and the second zero-crossing optocoupler are activated to simultaneously trigger the main thyristor and the auxiliary thyristor to conduct; After the main thyristor and the auxiliary thyristor are turned on, the current simultaneously flows through a running branch composed of a running winding and a starting branch composed of a phase enhancement component and a starting winding, wherein the phase enhancement component makes the current phase flowing through the starting branch lead the current phase flowing through the running branch by a predetermined range.

2. The single-phase induction motor control method based on starting phase enhancement according to claim 1, characterized in that, The predetermined range is 30° to 150°.

3. The single-phase induction motor control method based on starting phase enhancement according to claim 2, characterized in that, The phase enhancement component makes the current phase flowing through the starting branch lead the current phase flowing through the running branch by 90°.

4. The single-phase induction motor control method based on starting phase enhancement according to claim 1, characterized in that, The phase enhancement component is a thermistor.

5. The single-phase induction motor control method based on starting phase enhancement according to claim 4, characterized in that, One end of the running winding is electrically connected to the main thyristor, the other end of the running winding is electrically connected to the zero line of the alternating power supply, one end of the starting winding is electrically connected to the auxiliary thyristor, and the other end of the starting winding is electrically connected to the zero line of the alternating power supply.

6. The single-phase induction motor control method based on starting phase enhancement according to claim 1, characterized in that, The method further comprises the following steps: After the control unit detects that the motor has reached the normal running speed, the control unit stops sending the conduction signal to the second zero-crossing optocoupler for controlling the auxiliary thyristor; After the second zero-crossing optocoupler does not receive the conduction signal, the auxiliary thyristor remains on until the auxiliary thyristor is automatically turned off when the current next time passes through zero.

7. The single-phase induction motor control method based on starting phase enhancement according to claim 6, characterized in that, The method further comprises the following step: when the auxiliary thyristor is automatically turned off, the main thyristor remains on.

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