Water pump frequency converter on-load self-checking method

Abstract

The invention relates to the technical field of water pump variable frequency driving, in particular to a water pump frequency converter on-load self-checking method, which is characterized by comprising the following steps of: respectively sampling three-phase coils of a three-phase motor, and giving a specific driving signal under the condition of not influencing the normal work of a load; judgment is carried out through the signals fed back by the three-phase coil of the three-phase motor, and the change of the signals can be accurately judged and fed back according to the deviation condition of the signals and by comparing the record of the normal signals with the currently sampled data in advance, so that the fault condition of the three-phase motor is directly determined. According to the invention, fault detection and judgment can be carried out based on an existing hardware circuit structure under the condition of not increasing extra circuit and hardware cost, and detection and judgment can be carried out under the condition that the water pump motor does not stop working and is loaded.

Description

Technical Field

[0001] This invention relates to the technical field of variable frequency drive for water pumps, and specifically to a method for self-testing a variable frequency drive for water pumps under load. Background Technology

[0002] Variable frequency water pumps are becoming increasingly widely used. In practical applications, simple self-testing methods are typically employed to determine whether the circuit, motor, and wiring are functioning correctly. To ensure the normal operation of the variable frequency water pump, several simple self-testing methods are used to initially determine if there are any obvious faults in the circuit, motor, and wiring. These self-testing methods mainly include visual inspection, simple electrical parameter measurements, and basic operational tests. Visual inspection primarily checks for damage or deformation to the pump casing, and for loose or broken wiring. Electrical parameter measurements involve using tools such as multimeters to measure basic parameters such as voltage, current, and resistance to determine if they are within normal ranges. Basic operational tests involve running the water pump under low load or no-load conditions for a period of time, observing whether its operation is smooth and whether there is any abnormal noise.

[0003] However, existing simple self-testing methods have significant limitations, the most prominent being their inability to effectively detect abnormal motor parameters. As the core component of a variable frequency water pump, the accuracy of the motor's parameters directly affects the pump's performance and operational stability. Motor parameters include resistance, inductance, and torque constant, which can change due to manufacturing deviations, aging and wear after long-term operation, and moisture. For example, the resistance of the motor windings may increase due to insulation aging, leading to increased motor heating and reduced efficiency; changes in the motor's inductance parameters may affect its starting performance and speed control characteristics. However, existing self-testing methods cannot accurately measure and analyze these motor parameters, failing to detect abnormal changes in motor parameters in a timely manner, thus creating potential safety hazards for the subsequent operation of the water pump.

[0004] Besides failing to detect abnormal motor parameters, existing self-testing methods are also inadequate for comprehensively troubleshooting short circuits and open circuits. Short circuits and open circuits are common fault types in variable frequency water pump circuit systems. Short circuits can lead to excessive current in the circuit, causing serious consequences such as equipment damage or even fire; open circuits will prevent the water pump from working properly, affecting normal production and daily life. Although existing self-testing methods can make a preliminary judgment on the existence of short circuits or open circuits by measuring resistance, they often cannot accurately detect some hidden faults, such as poor contact or minor internal damage to the wiring. For example, in some complex wiring systems, loose or oxidized terminals may cause increased contact resistance. In the case of slight poor contact, the resistance measurement with a multimeter may not show obvious abnormalities, but during water pump operation, this poor contact may generate heat due to current flow, further aggravating the poor contact and ultimately leading to an open circuit fault. Moreover, existing self-testing methods can usually only test individual components or local circuits, making it difficult to comprehensively and systematically check for short circuits and open circuits in the entire water pump system, easily overlooking some potential fault points.

[0005] In summary, the existing self-testing technology for variable frequency water pumps has the following obvious defects: First, it lacks effective means to detect abnormal motor parameters when running under load, making it impossible to detect changes in motor performance in a timely manner, which affects the operational stability and service life of the water pump; second, it is not comprehensive and in-depth enough in troubleshooting short circuit and open circuit problems, making it difficult to detect some hidden faults, increasing the risk of water pump failure and causing inconvenience to production and daily life. Summary of the Invention

[0006] In order to solve the technical problems and shortcomings in the prior art, the present invention provides a method for self-testing of a frequency converter for water pumps under load, which can detect and judge abnormalities when the motor is running under load.

[0007] To achieve the above and other related objectives, the present invention adopts the following technical solution: A method for self-testing a frequency converter for a water pump under load includes a motor drive circuit, a three-phase motor, a filter circuit, and a microcontroller. The motor drive circuit has six bridge arms, and the control terminals of each bridge arm are: UH terminal, UL terminal, VH terminal, VL terminal, WH terminal, and WL terminal. The three ports of the three-phase coil in the three-phase motor are connected to the three sampling ports of the microcontroller through voltage divider resistors and filter circuits: ADC1, ADC2 and ADC3. The microcontroller detects the three voltage divider signals respectively: First, a high-frequency, low-duty-cycle drive signal is applied to the UH and VL terminals. The signal sent from the W phase is detected by the sampling port ADC1 of the microcontroller to obtain the result ZW. Next, the same driving signal is applied to the UH and WL terminals, and the signal sent from the V phase is detected by the sampling port ADC3 terminal in the microcontroller to obtain the result ZV. Then apply the same driving signal to the VH and WL terminals, and detect the signal sent from the U phase through the sampling port ADC2 terminal in the microcontroller to obtain the result ZU.

[0008] Preferably, the frequency range of the high-frequency low-duty-cycle drive signal is greater than or equal to 15KHz, and the duty cycle is less than or equal to 10%.

[0009] Preferably, the results ZW, ZV, and ZU are all average values ​​obtained by filtering multiple detection results.

[0010] Preferably, the microcontroller makes a judgment based on the results ZW, ZV, and ZU. If the three results ZW, ZV, and ZU are the same or close, it is determined that each phase coil is normal. Otherwise, the motor is considered faulty.

[0011] Preferably, one of the three results ZW, ZV, and ZU is deemed abnormal: If the value at the ADC1 terminal increases significantly, then the U-phase coil is short-circuited. If the value at the ADC1 terminal is significantly small or close to zero, then the U-phase coil is determined to be open-circuited. If the value at the ADC2 terminal increases significantly, then the problem is determined to be a short circuit in the V-phase coil. If the value at the ADC2 terminal is significantly small or close to zero, then the V-phase coil is determined to be open-circuited. If the value at ADC3 terminal increases significantly, then the cause is determined to be a short circuit in the W-phase coil. If the value at ADC3 is significantly small or close to zero, then the W-phase coil is determined to be open-circuited.

[0012] Preferably, a standard value Z0 is obtained in advance through experiments and saved to the microcontroller. The detected value is compared with the standard value. If the deviations of the three values ​​ZW, ZV, and ZU from the standard value Z0 are very small, it is determined to be normal. If there are differences between the three values ​​or differences from the standard value, it is determined to be abnormal.

[0013] Preferably, the deviation range of the three values ​​from the standard value Z0 is set to 5%.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention can directly determine whether the motor is malfunctioning and the type of malfunction by sampling and collecting signal changes during the operation of the motor under load and analyzing and comparing them, without adding any additional hardware structure to the existing hardware circuit.

[0015] 2. In this invention, it is possible to determine which circuit in a three-phase motor is faulty and to effectively determine the motor's operating status.

[0016] Other additional advantages and benefits of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 Circuit schematic diagram of an embodiment of this application; Figure 2 A simplified schematic diagram of one-channel detection in this embodiment of the application; Figure 3 The signals corresponding to UH and VL on the IGBT drive circuit in this embodiment of the application; Figure 4 The voltage signals at the midpoints of the U and V phase coils in the embodiments of this application; Figure 5 The signal sent to the ADC input terminal of the microcontroller in this embodiment of the application; Figure 6 : Detection flowchart in the embodiments of this application.

[0018] Explanation of reference numerals for major components: 100. Motor drive circuit; 200. IGBT drive circuit; 300. Motor; 400. Microcontroller. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. The following specific examples illustrate the embodiments of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0020] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The illustrations only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be changed at will, and the layout of the components may also be more complex.

[0021] It should be noted that in the description of this application, the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention. Furthermore, it should be noted that in the description of this application, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in the invention based on the specific circumstances.

[0022] Example: This invention discloses a method for self-testing a frequency converter for water pumps under load, wherein, as shown in the embodiments, Figure 1 The circuit diagram in the figure shows that the motor 300 drive and IGBT drive circuit 200 are conventional circuits and are not within the scope of protection of this invention.

[0023] The rectifier circuit consisting of transistor N1, relay K1, diode D1, rectifier B1, and resistor R1 is a conventional circuit and is not within the scope of protection of this invention. Figure 1 In this circuit, the JDQ signal terminal can be connected to one pin of the microcontroller 400. The base of transistor N1 is connected to the JDQ signal terminal, the emitter of transistor N1 is grounded, and the collector of transistor N1 is connected to the anode of diode D1 and one end of the coil of relay K1. The voltage source VDD is connected to the cathode of diode D1 and the other end of the coil of relay K1. The live wire and neutral wire are connected to the two input terminals of rectifier V1, respectively. One end of the rectifier's output terminal is grounded, and the other end is connected to the output power supply terminal V+ through resistor R1. The normally open switch of relay K1 is connected in parallel with resistor R1. The power supply V+ provides power to the motor 300 drive circuit 100, which is a bridge connection of six IGBTs used for frequency conversion and inversion. These circuits are added to clearly illustrate the principle.

[0024] Figure 1In the circuit, each port of the three-phase coil of the (three-phase AC) motor 300 is connected to a voltage divider resistor, namely R6, R8, R10, R5 and C1, R7 and C2, and R9 and C3, which are the corresponding RC filter circuits. The filtered signal is sent to the three ADC (ADC signal sampling) ports of the microcontroller 400 for detection. Diodes D2, D3, and D4 are clamping diodes. Connecting the clamping diodes to the voltage source VCC at the sampling terminal is to protect the sampling circuit and provide a reliable sampling signal.

[0025] Specifically, based on the aforementioned traditional hardware structure, the detection method of this solution is as follows: The three voltage divider signals (i.e., the three signals sent from the three-phase motor 300 to ADC1-3) are detected separately. First, a high-frequency, low-duty-cycle drive signal (e.g., 20kHz, 1% duty cycle) is applied to the UH and VL terminals of the motor 300 drive circuit 100. The signal from the W phase is detected by ADC1, yielding the result ZW. Next, the same drive signal is applied to the UH and WL terminals, and the signal from the V phase is detected by ADC3, yielding the result ZV. Finally, the same drive signal is applied to the VH and WL terminals, and the signal from the U phase is detected by ADC2, yielding the result ZU.

[0026] To illustrate this more clearly, we will specifically use a high-frequency, low-duty-cycle drive signal applied to the UH and VL terminals to detect the signal of phase W. Figure 2 This is a simplified schematic diagram for this situation.

[0027] When a drive signal is applied to the UH and VL terminals, current flows through the U-phase and V-phase coils of the motor 300. Because the duty cycle is relatively low, the current is small and will not affect the motor 300 or the circuit. The signal applied to the IGBT drive circuit 200 is as follows: Figure 3 As shown.

[0028] The IGBT at the UH terminal and the IGBT at the VL terminal are turned on simultaneously, applying voltage to the U and V phase coils.

[0029] When the IBGT transistor at the UH terminal is turned on, the upper end of the U-phase coil is at V+ voltage. When the IBGT transistor at the VL terminal is turned on, the lower end of the V-phase coil is connected to GND. This creates a voltage difference between the U and V coils. The signal waveform after voltage division between the two coils, i.e., the signal waveform at the connection point of U and V phases, is as follows: Figure 4 As shown, the signal is distorted due to the effect of the 300 coil of the motor, but this does not affect the detection.

[0030] The waveform after voltage division by the W-phase coil of the 300 MHz motor and resistor R6, followed by integration and filtering by resistor R5 and capacitor C1, is as follows: Figure 5As shown, this is also the signal directly sent to the sampling input terminal of the microcontroller's 400ADC. The signal amplitude is detected by the ADC to obtain the result ZW. ZW is the average value after multiple detection results and filtering. Usually, the method is to remove multiple maximum and minimum extreme values ​​and then average the remaining data.

[0031] The other two detection methods are the same and will not be repeated here.

[0032] When each phase coil is normal, since the three phase coils of motor 300 are the same, the detected results ZU, ZV, and ZW of the three ADC channels should be the same or close (for example, the deviation should not exceed 2%).

[0033] If a short circuit occurs in one phase or between two phases, it will inevitably cause a change in the signal. For example, if the U-phase coil is short-circuited, the voltage-divided signal will become significantly higher, the value of ADC1 will increase significantly, and it may even reach the maximum value of the sampled value.

[0034] If one phase is open-circuited, a phase with a signal of 0 will appear. For example, if phase U is open-circuited, V+ cannot be applied to the coil, so the value of ADC1 ZW will be 0 (or a very small value).

[0035] If there is an abnormality in a certain phase, such as an inter-turn short circuit in phase U, the voltage drop across the phase U coil will decrease, the voltage at the midpoint will be higher, and therefore the value of ADC1 will increase.

[0036] In practical applications, a standard value Z0 can be obtained in advance through experiments and saved to the microcontroller 400. The detected value is compared with the standard value. When everything is normal, the deviation of the three values ​​from the standard value Z0 is very small (e.g., less than 5%). If there is an anomaly, there will be differences not only among the three values ​​but also from the standard value. Analyzing these differences can help determine the fault condition and type.

[0037] exist Figure 6 The flowchart illustrating the operation of this method by the microcontroller 400 is shown in the image.

[0038] The microcontroller 400 detects the three voltage divider signals respectively: First, a high-frequency, low-duty-cycle drive signal is applied to the UH and VL terminals. The signal sent from the W phase is detected by the sampling port ADC1 of the microcontroller 400 to obtain the result ZW. Next, the same driving signal is applied to the UH and WL terminals, and the signal sent from the V phase is detected by the sampling port ADC3 of the microcontroller 400 to obtain the result ZV. Then apply the same driving signal to the VH and WL terminals, and detect the signal sent from the U phase through the sampling port ADC2 terminal in the microcontroller 400 to obtain the result ZU.

[0039] The results ZW, ZV, and ZU are all average values ​​obtained from multiple detections and filtering.

[0040] The microcontroller 400 makes a judgment based on the results ZW, ZV, and ZU. If the three results ZW, ZV, and ZU are the same or close, it is determined that each phase coil is normal. Otherwise, the motor is judged to be faulty (300 error).

[0041] Determine if one of the three results ZW, ZV, or ZU is abnormal: If the value at the ADC1 terminal increases significantly, then the U-phase coil is short-circuited. If the value at the ADC1 terminal is significantly small or close to zero, then the U-phase coil is determined to be open-circuited. If the value at the ADC2 terminal increases significantly, then the problem is determined to be a short circuit in the V-phase coil. If the value at the ADC2 terminal is significantly small or close to zero, then the V-phase coil is determined to be open-circuited. If the value at ADC3 terminal is significantly larger (too large), then the cause is determined to be a short circuit in the W-phase coil. If the value at ADC3 is significantly small or close to zero, then the W-phase coil is determined to be open-circuited.

[0042] If the three data points differ significantly from Z0, then all three phases are abnormal, which can be used for alarm indication.

[0043] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for self-testing a frequency converter for a water pump under load, comprising a motor (300) drive circuit (100), a three-phase motor (300), a filter circuit, and a microcontroller (400). The motor (300) drive circuit (100) has six bridge arms, and the control terminals of each bridge arm are: UH terminal, UL terminal, VH terminal, VL terminal, WH terminal, and WL terminal. The three ports of the three-phase coil in the three-phase motor (300) are connected to the three sampling ports of the microcontroller (400) through voltage divider resistors and filter circuits: ADC1, ADC2 and ADC3. Its features are, The microcontroller (400) detects the three voltage divider signals respectively: First, a high-frequency, low-duty-cycle drive signal is applied to the UH and VL terminals. The signal sent from the W phase is detected by the sampling port ADC1 of the microcontroller (400) to obtain the result ZW. Next, the same driving signal is applied to the UH and WL terminals, and the signal sent from the V phase is detected by the sampling port ADC3 terminal in the microcontroller (400) to obtain the result ZV; Then apply the same driving signal to the VH and WL terminals, and detect the signal sent from the U phase through the sampling port ADC2 terminal in the microcontroller (400) to obtain the result ZU.

2. The method for self-testing a frequency converter for a water pump under load according to claim 1, characterized in that, The frequency range of the high-frequency low duty cycle drive signal is greater than or equal to 15KHz, and the duty cycle is less than or equal to 10%.

3. The method for self-testing a frequency converter for a water pump under load according to claim 1, characterized in that, The results ZW, ZV, and ZU are all average values ​​obtained from multiple detections and filtering.

4. The method for self-testing a frequency converter for a water pump under load according to claim 1, characterized in that, The microcontroller (400) makes a judgment based on the results ZW, ZV, and ZU. If the three results ZW, ZV, and ZU are the same or close, it is determined that each phase coil is normal. Otherwise, the motor (300) is deemed to be malfunctioning.

5. A method for self-testing a frequency converter for a water pump under load, as described in claim 4, is characterized in that... Determine if one of the three results ZW, ZV, or ZU is abnormal: If the value at the ADC1 terminal increases significantly, then the U-phase coil is short-circuited. If the value at the ADC1 terminal is significantly small or close to zero, then the U-phase coil is determined to be open-circuited. If the value at the ADC2 terminal increases significantly, then the problem is determined to be a short circuit in the V-phase coil. If the value at the ADC2 terminal is significantly small or close to zero, then the V-phase coil is determined to be open-circuited. If the value at ADC3 terminal increases significantly, then the cause is determined to be a short circuit in the W-phase coil. If the value at ADC3 is significantly small or close to zero, then the W-phase coil is determined to be open-circuited.

6. A method for self-testing a frequency converter for a water pump under load according to claim 1, characterized in that, The standard value Z0 is obtained in advance through experiments and saved to the microcontroller (400). The detected value is compared with the standard value. If the deviations of the three values ​​ZW, ZV and ZU from the standard value Z0 are very small, they are determined to be normal. If there are differences between the three values ​​or differences from the standard value, they are determined to be abnormal.

7. A method for self-testing a frequency converter for a water pump under load according to claim 6, characterized in that, The deviation range of the three values ​​from the standard value Z0 is set to 5%.

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