Control circuit and control method of three-phase motor

Abstract

The invention provides a control circuit and a control method of a three-phase motor. The control circuit comprises a starting controller, an angle predictor, a safety controller and a PWM generator. And the angle predictor is electrically connected with the starting controller and is used for obtaining a pre-estimated angle of operation of the three-phase motor and generating a half-cycle signal and a sine and cosine signal according to the pre-estimated angle. And the starting controller is used for generating a motor control signal according to each phase current and sine and cosine signals of the three-phase motor. And the safety controller is used for detecting whether the three-phase motor is open-phase or not according to each phase current and the half-cycle signal of the three-phase motor and generating a safety control signal. The safety control signal is used for shutting down the three-phase motor when the three-phase motor is open-phase. The PWM generator is electrically connected with the three-phase motor, the starting controller and the safety controller and used for controlling the three-phase motor to operate according to the motor control signal and the safety control signal. Whether the motor is open-phase or not can be detected through hardware.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a control circuit and control method for a three-phase motor. Background Technology

[0002] During operation, a motor may experience a phase loss, meaning one phase of power is missing from the three-phase circuit. This reduces the motor's torque and rotor speed, causing the current in the other two phases to increase and potentially burn out the motor windings. A phase loss can lead to unstable motor operation and even damage the motor.

[0003] Phase loss protection methods generally include current protection, voltage protection, thermal protection, and phase sequence protection. These methods monitor current, voltage, temperature, and phase sequence respectively. If a phase loss occurs, the power supply is cut off and the motor stops running in time to avoid burning out the windings.

[0004] For phase loss detection, a software timing method is typically used. If the current remains below a threshold for a certain period, the power is cut off to stop the motor. This method requires significant CPU resources, hindering other CPU operations. Furthermore, the detection time needs to be set by the user and is related to the motor speed. Users often struggle to accurately determine motor speed and other information, making the setup cumbersome and prone to setting the detection time too short or too long. Setting the detection time too short may result in accidental motor shutdown, while setting it too long may prevent timely shutdown. Summary of the Invention

[0005] This application provides a control circuit and control method for a three-phase motor implemented in hardware, which consumes less CPU resources and is easy to test.

[0006] This application provides a control circuit for a three-phase motor, including: a starter controller, an angle predictor, a safety controller, and a PWM generator;

[0007] The angle predictor is electrically connected to the start controller and is used to obtain the predicted angle of the three-phase motor operation, and generate a half-cycle signal and a sine and cosine signal based on the predicted angle.

[0008] The start controller is electrically connected to the three-phase motor and the angle predictor, and is used to generate motor control signals based on the phase currents of the three-phase motor and the sine and cosine signals.

[0009] The safety controller is electrically connected to the start controller and the angle predictor, and is used to detect whether the three-phase motor is missing a phase based on the phase current of each phase of the three-phase motor and the half-cycle signal, and generate a safety control signal; the safety control signal is used to: shut down the three-phase motor when a phase is missing.

[0010] The PWM generator is electrically connected to the three-phase motor, the start controller, and the safety controller, and is used to control the operation of the three-phase motor according to the motor control signal and the safety control signal.

[0011] Optionally, the safety controller includes a safety control module, which includes a comparison circuit and a timing circuit. The first input terminal of the comparison circuit receives the current value signal of the three-phase motor, and the second input terminal receives a current threshold signal. The first and second output terminals of the comparison circuit are respectively connected to the first and second input terminals of the timing circuit. The comparison circuit outputs a comparison result signal based on the current value signal of the three-phase motor and the current threshold signal. The third input terminal of the timing circuit receives the half-cycle signal. The timing circuit generates the safety control signal when the current value signal of the three-phase motor is less than the current threshold signal and the duration reaches the duration represented by the half-cycle signal.

[0012] Optionally, the fourth input terminal of the timing circuit is used to receive a setting signal. The timing circuit is used to generate the safety control signal when the half-cycle signal is missing, the current value signal of the three-phase motor is less than the current threshold signal, and the duration reaches the duration represented by the setting signal.

[0013] Optionally, the timing circuit includes a first timing circuit, a second timing circuit, and a first OR gate circuit, wherein,

[0014] The first input terminal of the first timing circuit is used to receive the half-cycle signal, the second input terminal of the first timing circuit is connected to the first output terminal of the comparison circuit, and the first timing circuit is used to output a first safety control signal according to the comparison result signal and the half-cycle signal.

[0015] The first input terminal of the second timing circuit is used to receive the setting signal, the second input terminal of the second timing circuit is connected to the second output terminal of the comparison circuit, and the second timing circuit is used to output a second safety control signal according to the comparison result signal and the setting signal;

[0016] The first input terminal of the first OR gate is used to receive the first safety control signal, the second input terminal of the first OR gate is used to receive the second safety control signal, and the first OR gate is used to output the safety control signal.

[0017] Optionally, the first timing circuit includes: a first multiplexer, a second multiplexer, a first flip-flop, and an AND gate circuit; the first input terminal of the first multiplexer is connected to the output terminal of the first flip-flop, the second input terminal of the first multiplexer is used to receive a low-level signal, and the control terminal of the first multiplexer is connected to the first output terminal of the comparator circuit; the output terminal of the first multiplexer is connected to the first input terminal of the second multiplexer, the second input terminal of the second multiplexer is used to receive a high-level signal, and the control terminal of the second multiplexer is used to receive the half-cycle signal; the output terminal of the second multiplexer is connected to the input terminal of the first flip-flop, the output terminal of the first flip-flop is connected to the first input terminal of the AND gate circuit, the second input terminal of the AND gate circuit is used to receive the half-cycle signal, and the AND gate circuit is used to output the first safety control signal.

[0018] Optionally, the second timing circuit includes: a second OR gate, an adder, a third multiplexer, a fourth multiplexer, a second flip-flop, and a comparator;

[0019] The input terminals of the second OR gate circuit are respectively used to receive the half-cycle signal and the second safety control signal, and are connected to the first output terminal of the comparator circuit;

[0020] The first input terminal of the adder is used to receive a high-level signal, and the second input terminal of the adder is connected to the output terminal of the second flip-flop;

[0021] The first input terminal of the third multiplexer is connected to the output terminal of the second flip-flop, the second input terminal of the third multiplexer is connected to the output terminal of the adder, and the control terminal of the third multiplexer is connected to the second output terminal of the comparator circuit.

[0022] The first input terminal of the fourth multiplexer is connected to the output terminal of the third multiplexer, the second input terminal of the fourth multiplexer is used to receive low-level signals, and the control terminal of the fourth multiplexer is connected to the output terminal of the second OR gate circuit.

[0023] The input of the second flip-flop is connected to the output of the fourth multiplexer;

[0024] The first input terminal of the comparator is connected to the output terminal of the second flip-flop, the second input terminal of the comparator is used to receive the setting signal, and the comparator is used to output the second safety control signal.

[0025] Optionally, the safety control module further includes a restart circuit, which is connected to the first output terminal of the comparison circuit and the output terminal of the timing circuit. The restart circuit is used to reset the safety control signal so that the three-phase motor restarts when the comparison result signal indicates that the current of the three-phase motor is not less than the current threshold represented by the current threshold signal.

[0026] Optionally, the safety controller includes three safety control modules, each of which receives a one-phase current value signal from the three-phase motor.

[0027] This application also provides a control method for a three-phase motor, applied to a control circuit of a three-phase motor as described in any of the above claims, the control method comprising:

[0028] Obtain the current of each phase of the three-phase motor;

[0029] The estimated angle of the three-phase motor is obtained based on the phase current of each phase of the three-phase motor, and a half-cycle signal is generated based on the estimated angle.

[0030] If the current in each phase is greater than the current threshold, the three-phase motor is controlled to operate normally.

[0031] If the current in any phase of the three-phase motor is less than the current threshold and the duration reaches the duration represented by the half-cycle signal, the three-phase motor is shut down.

[0032] Optionally, the control method further includes:

[0033] When the half-cycle signal is missing, if the current in any phase of the three-phase motor is less than the current threshold and the duration reaches a preset duration, the three-phase motor is shut down.

[0034] In some embodiments, the control circuit includes: a start controller, an angle predictor, a safety controller, and a PWM generator; the start controller generates motor control signals based on the phase currents and sine / cosine signals of the three-phase motor to control the motor to operate normally; the angle predictor obtains the estimated angle of the three-phase motor and generates half-cycle signals and sine / cosine signals based on the estimated angle; the safety controller detects whether the three-phase motor is missing a phase based on the phase currents and half-cycle signals of the three-phase motor and generates a safety control signal to shut down the three-phase motor when a phase loss occurs; thus, the control circuit detects whether the motor is missing a phase and can automatically shut down the motor when a phase loss occurs, without the need for software detection, consuming less CPU resources, and without the need to set the detection time, making detection simpler.

[0035] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0037] Figure 1 The diagram shown is a structural block diagram of one embodiment of the control circuit for a three-phase motor according to this application.

[0038] Figure 2 As shown Figure 1 The diagram shows a structural block diagram of one embodiment of the security controller.

[0039] Figure 3 As shown Figure 2 The circuit diagram shown is an embodiment of the timing circuit.

[0040] Figure 4 The diagram shown is a flowchart of one embodiment of the control method for a three-phase motor according to this application. Detailed Implementation

[0041] This application provides a control circuit and control method for a three-phase motor. The control circuit and control method for the three-phase motor of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments and implementations can be combined with each other.

[0042] Figure 1 The diagram shown is a structural block diagram of one embodiment of the control circuit 10 for a three-phase motor according to this application. Figure 1 As shown, the control circuit 10 of the three-phase motor includes: a start controller 11, an angle predictor 12, a safety controller 13, and a PWM generator 14.

[0043] Angle predictor 12 is electrically connected to starter controller 11 to obtain the predicted angle of operation of three-phase motor 20, and to generate half-cycle signal and sine and cosine signals based on the predicted angle.

[0044] Angle predictor 12 receives current i in a stationary two-phase orthogonal coordinate system generated by start controller 11. α i β Orthogonal voltage v in stationary two-phase coordinate system α v β The estimated angle of the three-phase motor 20 is obtained through the slid film observer.

[0045] The sine and cosine signals are calculated by estimating the angle, and the current signal used for the three-phase motor 20 is transformed between the two-phase stationary coordinate system and the two-phase rotating coordinate system.

[0046] The start controller 11 is electrically connected to the three-phase motor 20 and the angle predictor 12, and is used to generate motor control signals based on the phase currents and sine and cosine signals of the three-phase motor 20.

[0047] The start controller 11 collects the three-phase stator current i of the three-phase motor 20. a i b i c The three-phase stator current i a i b i c The current i in the stationary two-phase orthogonal coordinate system is generated by Clarke transformation. α i β The start controller 11 is electrically connected to the angle predictor 12, receiving the sine and cosine signals generated by the angle predictor 12. After Park transformation, PID calculation, and inverse Park transformation, it generates an orthogonal voltage v in a stationary two-phase coordinate system. α v β Finally, the duty cycle value of the PWM signal is calculated using Clarke inverse transform and SVPWM control algorithm. The start controller 11 sends this duty cycle value to the PWM generator 14 to adjust the speed, torque or other operating characteristics of the three-phase motor 20.

[0048] The start controller 11 will also start the three-phase stator current i a i b i c The absolute values ​​of the three-phase currents IU, IV, and IW are obtained and sent to the safety controller 13 to determine whether a phase loss fault has occurred in each phase.

[0049] The safety controller 13 is electrically connected to the start controller 11 and the angle predictor 12. It is used to detect whether the three-phase motor 20 is missing a phase based on the phase current of each phase and the half-cycle signal, and to generate a safety control signal. The safety control signal is used to shut down the three-phase motor 20 when a phase loss occurs.

[0050] The safety controller 13 receives the three-phase current values ​​IU, IV, and IW generated by the start controller 11 and the half-cycle signal generated by the angle predictor 12. It determines whether a phase loss has occurred in the three-phase motor 20 within the duration represented by the half-cycle signal. If a phase loss occurs, it generates a safety control signal and sends it to the PWM generator 14 to control the three-phase motor 20 to shut down. Thus, when a phase loss fault occurs in the three-phase motor 20, it can be automatically and promptly shut down, preventing damage to the three-phase motor 20.

[0051] The PWM generator 14 is electrically connected to the three-phase motor 20, the starter controller 11, and the safety controller 13, and is used to control the operation of the three-phase motor 20 according to the motor control signal and the safety control signal.

[0052] The PWM generator 14 generates PWM signals to control the operation of the three-phase motor 20 based on the motor control signal and the safety control signal. The PWM signal adjusts the voltage and current of the three-phase motor 20 by changing the pulse width, thereby achieving precise control of parameters such as the speed and torque of the three-phase motor 20. The PWM generator 14 controls the operation of the three-phase motor 20 according to the motor control signal and controls the three-phase motor 20 to shut down according to the safety control signal.

[0053] In some embodiments, the start controller 11 is used to generate a motor control signal based on the phase currents and sine and cosine signals of the three-phase motor 20 to control the motor to operate normally; the angle predictor 12 is used to obtain the estimated angle of the three-phase motor 20 and generate a half-cycle signal and sine and cosine signals based on the estimated angle; the safety controller 13 is used to detect whether the three-phase motor 20 is missing a phase based on the phase currents and half-cycle signals of the three-phase motor 20, and generate a safety control signal to shut down the three-phase motor when a phase loss occurs; thus, the control circuit 10 can detect whether the motor is missing a phase and automatically shut down the motor when a phase loss occurs, without the need for software detection, which consumes less CPU resources and does not require setting the detection time, making detection simpler.

[0054] Figure 2 As shown Figure 1 The diagram shows a structural block diagram of one embodiment of the safety controller 13.

[0055] The safety controller 13 includes a safety control module 130. The safety control module 130 includes a comparator circuit 131 and a timing circuit 132.

[0056] The first input terminal of the comparator circuit 131 is used to receive the current value signal of the three-phase motor 20, and the second input terminal of the comparator circuit 131 is used to receive the current threshold signal.

[0057] The first and second output terminals of the comparator circuit 131 are respectively connected to the first and second input terminals of the timing circuit 132. The comparator circuit 131 is used to output a comparison result signal based on the current value signal and the current threshold signal of the three-phase motor 20.

[0058] Taking the detection of the U-phase current of a three-phase motor 20 as an example, the first input terminal of the comparator circuit 131 is connected to the U-phase. The current threshold signal is preset. The current threshold signal can be set by the user. When the U-phase current IU is greater than the current threshold, it indicates that the U-phase current has not exceeded the limit and the U-phase has not lost a phase. The first output terminal of the comparator circuit 131 outputs 1, and the second output terminal outputs 0. Conversely, it indicates that the U-phase current has exceeded the limit and the U-phase has lost a phase. The first output terminal of the comparator circuit 131 outputs 0, and the second output terminal outputs 1.

[0059] The third input terminal of the timing circuit 132 is used to receive the half-cycle signal T1. The timing circuit 132 is used to generate a safety control signal when the current value signal of the three-phase motor 20 is less than the current threshold signal and the duration reaches the duration represented by the half-cycle signal T1.

[0060] The timing circuit 132 is used for timing. When the comparison result signal indicates that a phase loss has occurred in the three-phase motor 20, the timing circuit 132 starts timing. When the timing reaches the duration represented by the half-cycle signal T1, a safety control signal for shutting down the three-phase motor 20 is generated. In this way, when a phase loss occurs in the three-phase motor 20, the motor will not be shut down immediately. The motor will only be shut down when the duration of the phase loss reaches the duration represented by the half-cycle signal T1, thus avoiding accidental motor shutdown.

[0061] The fourth input terminal of the timing circuit 132 is used to receive the setting signal R1. The timing circuit 132 is used to generate a safety control signal when the half-cycle signal T1 is missing, the current value signal of the three-phase motor 20 is less than the current threshold signal, and the duration reaches the duration represented by the setting signal R1.

[0062] The setting signal R1 is used to provide timing basis for the timing circuit 132 when the half-cycle signal T1 is missing. The duration represented by the setting signal R1 should be greater than the duration represented by the half-cycle signal T1. When the timing circuit 132 does not receive the half-cycle signal T1, and the comparison result signal indicates that the three-phase motor 20 has lost a phase, the timing circuit 132 starts timing. When the timing reaches the duration represented by the setting signal R1, a safety control signal for shutting down the three-phase motor 20 is generated.

[0063] The safety control module 130 also includes a restart circuit 133. The restart circuit 133 is connected to the first output terminal of the comparison circuit 131 and the output terminal of the timing circuit 132, and is used to reset the safety control signal so that the three-phase motor 20 restarts when the current value signal of the three-phase motor 20 is not less than the current threshold signal.

[0064] The output of restart circuit 133 is connected to PWM generator 14. When the current signal of three-phase motor 20 is not less than the current threshold signal, it indicates that the motor is no longer in a phase loss state. At this time, restart circuit 133 resets the safety control signal and restarts the motor. The output of timing circuit 132 is connected to the input of restart circuit 133, and timing circuit 132 sends a safety control signal to restart circuit 133.

[0065] Taking the U-phase current of the three-phase motor 20 as an example, when a phase loss occurs in the U-phase, the first output terminal of the comparator circuit 131 outputs 0, the timing circuit 132 outputs a safety control signal, and the restart circuit 133 controls the three-phase motor 20 to shut down according to the safety control signal. When no phase loss occurs in the U-phase, the first output terminal of the comparator circuit 131 outputs 1. When the restart circuit 133 receives a high-level signal, it resets the safety control signal and controls the three-phase motor 20 to restart.

[0066] The restart circuit 133 can automatically resume motor operation, preventing the motor from being stopped for a long time.

[0067] In some embodiments, the safety controller 13 includes three safety control modules 130, each of which receives a one-phase current value signal from the three-phase motor 20. Each safety control module 130 is used to detect whether a phase loss has occurred in one phase of the three-phase motor 20, and when the phase loss reaches the duration represented by the half-cycle signal T1 or the duration represented by the setting signal R1, it controls the three-phase motor 20 to shut down, thereby protecting the three-phase motor 20.

[0068] Figure 3 As shown Figure 2 The circuit diagram shows one embodiment of the timing circuit 132.

[0069] The timing circuit 132 includes a first timing circuit 31, a second timing circuit 32, and a first OR gate circuit 33. The first input terminal of the first timing circuit 31 is used to receive a half-cycle signal T1, and the second input terminal of the first timing circuit 31 is connected to the first output terminal of the comparison circuit 131. The first timing circuit 31 is used to output a first safety control signal W1 based on the comparison result signal and the half-cycle signal T1.

[0070] The first input terminal of the second timing circuit 32 is used to receive the setting signal R1. The second input terminal of the second timing circuit 32 is connected to the second output terminal of the comparison circuit 131. The second timing circuit 32 is used to output the second safety control signal W2 according to the comparison result signal and the setting signal R1.

[0071] The first input terminal of the first OR gate circuit 33 is used to receive the first safety control signal W1, the second input terminal of the first OR gate circuit is used to receive the second safety control signal W2, and the first OR gate circuit 33 is used to output the safety control signal.

[0072] The first timing circuit 31 is used to determine whether the duration of the motor phase loss reaches the duration represented by the half-cycle signal T1 when the half-cycle signal T1 is received. The first safety control signal W1 is used to shut down the motor when the duration of the motor phase loss reaches the duration represented by the half-cycle signal T1.

[0073] The second timing circuit 32 is used to determine whether the duration of the motor phase loss has reached the duration indicated by the setting signal R1 when the half-cycle signal T1 is not received. The second safety control signal W2 is used to shut down the motor when the duration of the motor phase loss reaches the duration indicated by the setting signal R1.

[0074] The safety control signal is generated by ORing the first safety control signal W1 and the second safety control signal W2. When either the first safety control signal W1 or the second safety control signal W2 is high, the safety control signal is high.

[0075] The first timing circuit 31 includes: a first multiplexer A1, a second multiplexer A2, a first flip-flop A3, and an AND gate circuit A4.

[0076] The first input terminal of the first multiplexer A1 is connected to the output terminal of the first flip-flop A3. The second input terminal of the first multiplexer A1 is used to receive a low-level signal. The control terminal of the first multiplexer A1 is connected to the first output terminal of the comparator circuit 131. The low-level signal can be generated by an external circuit or by the ground terminal of the control circuit of this application. The low-level signal is implemented using existing technology.

[0077] The output of the first multiplexer A1 is connected to the first input of the second multiplexer A2. The second input of the second multiplexer A2 is used to receive a high-level signal, and the control terminal of the second multiplexer A2 is used to receive a half-cycle signal T1. The high-level signal can be generated by an external circuit or by the power supply terminal of the control circuit of this application. The high-level signal is implemented using existing technology.

[0078] The output of the second multiplexer A2 is connected to the input of the first flip-flop A3. The output of the first flip-flop A3 is connected to the first input of the AND gate A4. The second input of the AND gate A4 is used to receive the half-cycle signal T1. The AND gate A4 is used to output the first safety control signal W1.

[0079] Taking the detection of the U-phase current of a motor as an example. When a phase loss occurs in the U-phase, the first output terminal of the comparator circuit 131 outputs 0, and the second output terminal outputs 1. The control terminal of the first multiplexer A1 is input to 0, and the output terminal of the first multiplexer outputs 1. When the half-cycle signal T1 is active, the half-cycle signal T1 is at a high level. The control terminal of the second multiplexer A2 is input to 1, the output terminal of the second multiplexer A2 outputs 1, the first flip-flop A3 outputs 1, and the first safety control signal W1 output by the AND gate circuit A4 is 1.

[0080] The second timing circuit 32 includes: a second OR gate circuit A5, an adder A6, a third multiplexer A7, a fourth multiplexer A8, a second flip-flop A9, and a comparator A10.

[0081] The input terminals of the second OR gate circuit A5 are used to receive the half-cycle signal T1 and the second safety control signal W2, respectively, and are connected to the first output terminal of the comparator circuit 131.

[0082] The first input terminal of adder A6 is used to receive a high-level signal, and the second input terminal of adder A6 is connected to the output terminal of the second flip-flop A9.

[0083] The first input terminal of the third multiplexer A7 is connected to the output terminal of the second flip-flop A9, the second input terminal of the third multiplexer A7 is connected to the output terminal of the adder A6, and the control terminal of the third multiplexer A7 is connected to the second output terminal of the comparator circuit 131.

[0084] The first input terminal of the fourth multiplexer A8 is connected to the output terminal of the third multiplexer A7. The second input terminal of the fourth multiplexer A8 is used to receive low-level signals. The control terminal of the fourth multiplexer A8 is connected to the output terminal of the second OR gate circuit A5.

[0085] The input of the second flip-flop A9 is connected to the output of the fourth multiplexer A8.

[0086] The first input terminal of comparator A10 is connected to the output terminal of the second flip-flop A9. The second input terminal of comparator A10 is used to receive the setting signal R1. Comparator A10 is used to output the second safety control signal W2.

[0087] The second OR gate A5 is used to generate the clear signal W3. The clear signal W3 is generated by ORing the half-cycle signal T1, the output signal of the first output terminal of the comparator circuit 131, and the second safety control signal W2. The second flip-flop A9 outputs 0 by default. When the clear signal W3 is 1, the output of the second flip-flop A9 is cleared. When the half-cycle signal T1 is 1, the clear signal W3 is 1, and the output of the second flip-flop A9 is cleared, therefore the setting signal R1 is not used. The setting signal R1 is used only when the half-cycle signal T1 is 0, and the setting signal R1 acts as a substitute for the half-cycle signal T1. When the clear signal W3 is 0, and the second output terminal of the comparator circuit 131 outputs 1, the output of the second flip-flop A9 is incremented by 1. When the output of the second flip-flop A9 is equal to the setting signal R1, the second safety control signal W2 output by the comparator A10 is 1.

[0088] Taking the detection of the U-phase current of a motor as an example. When a phase loss occurs in the U-phase, the first output terminal of the comparator circuit 131 outputs 0, and the second output terminal outputs 1. When no half-cycle signal T1 is received, the half-cycle signal T1 is 0. The setting signal R1 is 400. The clear signal W3 is 0. The output of adder A6 is incremented by 1, the outputs of the third multiplexer A7 and the fourth multiplexer A8 are incremented by 1, and the output of the second flip-flop A9 is incremented by 1. When the output of the second flip-flop A9 is equal to the setting signal R1, the second safety control signal W2 is 1.

[0089] Figure 4 The diagram shown is a flowchart of one embodiment of the three-phase motor control method 40 of this application.

[0090] The three-phase motor control method 40 is applied to the three-phase motor control circuit 10 as described above. The control method 40 includes steps 41 to 46.

[0091] Step 41: Obtain the current of each phase of the three-phase motor.

[0092] Step 42: Obtain the estimated angle of the three-phase motor operation based on the phase current of each phase of the three-phase motor, and generate a half-cycle signal based on the estimated angle.

[0093] Step 43: Determine whether the current in each phase is greater than the current threshold.

[0094] Step 44: If the current of each phase is greater than the current threshold, control the three-phase motor to operate normally.

[0095] Step 45: If the current of any phase of the three-phase motor is less than the current threshold, determine whether the duration of the current of that phase being less than the current threshold reaches the duration represented by the half-cycle signal.

[0096] Step 46: If the duration reaches the duration represented by a half-cycle signal, shut down the three-phase motor.

[0097] By analyzing the current in each phase of a three-phase motor, it is possible to determine whether a phase loss fault has occurred. A half-cycle signal serves as the time reference for this determination. If all phase currents are greater than their respective thresholds, it indicates that no phase loss has occurred, and the motor can be controlled to operate normally. If any phase current is less than its threshold, and the duration reaches the duration indicated by the half-cycle signal, it indicates a phase loss for that phase. In this case, the motor should be shut down to protect it from damage.

[0098] In some embodiments, the control method 40 further includes: when a half-cycle signal is missing, if the current in any phase of the three-phase motor is less than a current threshold and the duration reaches a preset duration, shutting down the three-phase motor. The preset duration should be greater than the duration represented by the half-cycle signal. Thus, even when a half-cycle signal is missing, it is possible to detect whether a phase loss fault has occurred in the motor and shut down the motor in a timely manner.

Claims

1. A control circuit for a three-phase motor, characterized in that, include: Start-up controller, angle predictor, safety controller, and PWM generator; The angle predictor is electrically connected to the start controller and is used to obtain the predicted angle of the three-phase motor operation, and generate a half-cycle signal and a sine and cosine signal based on the predicted angle. The start controller is electrically connected to the three-phase motor and the angle predictor, and is used to generate motor control signals based on the phase currents of the three-phase motor and the sine and cosine signals. The safety controller is electrically connected to the start controller and the angle predictor, and is used to detect whether the three-phase motor is missing a phase based on the phase current of each phase of the three-phase motor and the half-cycle signal, and generate a safety control signal; the safety control signal is used to: shut down the three-phase motor when a phase is missing. The PWM generator is electrically connected to the three-phase motor, the start controller, and the safety controller, and is used to control the operation of the three-phase motor according to the motor control signal and the safety control signal.

2. The control circuit for a three-phase motor according to claim 1, characterized in that, The safety controller includes a safety control module, which includes a comparison circuit and a timing circuit. The first input terminal of the comparison circuit receives the current value signal of the three-phase motor, and the second input terminal receives a current threshold signal. The first and second output terminals of the comparison circuit are respectively connected to the first and second input terminals of the timing circuit. The comparison circuit compares the current value signal of the three-phase motor with the current threshold signal and outputs a comparison result signal. The third input terminal of the timing circuit receives the half-cycle signal. The timing circuit generates the safety control signal when the current value signal of the three-phase motor is less than the current threshold signal and the duration reaches the duration represented by the half-cycle signal.

3. The control circuit for a three-phase motor according to claim 2, characterized in that, The fourth input terminal of the timing circuit is used to receive a setting signal. The timing circuit is used to generate the safety control signal when the half-cycle signal is missing, the current value signal of the three-phase motor is less than the current threshold signal, and the duration reaches the duration represented by the setting signal.

4. The control circuit for a three-phase motor according to claim 3, characterized in that, The timing circuit includes a first timing circuit, a second timing circuit, and a first OR gate circuit, wherein... The first input terminal of the first timing circuit is used to receive the half-cycle signal, the second input terminal of the first timing circuit is connected to the first output terminal of the comparison circuit, and the first timing circuit is used to output a first safety control signal according to the comparison result signal and the half-cycle signal. The first input terminal of the second timing circuit is used to receive the setting signal, the second input terminal of the second timing circuit is connected to the second output terminal of the comparison circuit, and the second timing circuit is used to output a second safety control signal according to the comparison result signal and the setting signal; The first input terminal of the first OR gate is used to receive the first safety control signal, the second input terminal of the first OR gate is used to receive the second safety control signal, and the first OR gate is used to output the safety control signal.

5. The control circuit for a three-phase motor according to claim 4, characterized in that, The first timing circuit includes: a first multiplexer, a second multiplexer, a first flip-flop, and an AND gate circuit; the first input terminal of the first multiplexer is connected to the output terminal of the first flip-flop, the second input terminal of the first multiplexer is used to receive a low-level signal, and the control terminal of the first multiplexer is connected to the first output terminal of the comparator circuit; the output terminal of the first multiplexer is connected to the first input terminal of the second multiplexer, the second input terminal of the second multiplexer is used to receive a high-level signal, and the control terminal of the second multiplexer is used to receive the half-cycle signal; the output terminal of the second multiplexer is connected to the input terminal of the first flip-flop, the output terminal of the first flip-flop is connected to the first input terminal of the AND gate circuit, the second input terminal of the AND gate circuit is used to receive the half-cycle signal, and the AND gate circuit is used to output the first safety control signal.

6. The control circuit for a three-phase motor according to claim 4, characterized in that, The second timing circuit includes: a second OR gate, an adder, a third multiplexer, a fourth multiplexer, a second flip-flop, and a comparator; The input terminals of the second OR gate circuit are respectively used to receive the half-cycle signal and the second safety control signal, and are connected to the first output terminal of the comparator circuit; The first input terminal of the adder is used to receive a high-level signal, and the second input terminal of the adder is connected to the output terminal of the second flip-flop; The first input terminal of the third multiplexer is connected to the output terminal of the second flip-flop, the second input terminal of the third multiplexer is connected to the output terminal of the adder, and the control terminal of the third multiplexer is connected to the second output terminal of the comparator circuit. The first input terminal of the fourth multiplexer is connected to the output terminal of the third multiplexer, the second input terminal of the fourth multiplexer is used to receive low-level signals, and the control terminal of the fourth multiplexer is connected to the output terminal of the second OR gate circuit. The input of the second flip-flop is connected to the output of the fourth multiplexer; The first input terminal of the comparator is connected to the output terminal of the second flip-flop, the second input terminal of the comparator is used to receive the setting signal, and the comparator is used to output the second safety control signal.

7. The control circuit for a three-phase motor according to claim 2, characterized in that, The safety control module further includes a restart circuit, which is connected to the first output terminal of the comparison circuit and the output terminal of the timing circuit. When the comparison result signal indicates that the current of the three-phase motor is not less than the current threshold represented by the current threshold signal, the restart circuit resets the safety control signal to restart the three-phase motor.

8. The control circuit for a three-phase motor according to claim 2, characterized in that, The safety controller includes three safety control modules, each of which receives a one-phase current value signal from the three-phase motor.

9. A control method for a three-phase motor, applied to the control circuit of the three-phase motor as described in any one of claims 1-8, the control method comprising: Obtain the current of each phase of the three-phase motor; The estimated angle of the three-phase motor is obtained based on the phase current of each phase of the three-phase motor, and a half-cycle signal is generated based on the estimated angle. If the current in each phase is greater than the current threshold, the three-phase motor is controlled to operate normally. If the current in any phase of the three-phase motor is less than the current threshold and the duration reaches the duration represented by the half-cycle signal, the three-phase motor is shut down.

10. The control method for a three-phase motor according to claim 9, characterized in that, The control method further includes: When the half-cycle signal is missing, if the current of any phase of the three-phase motor is less than the current threshold and the duration reaches the preset duration, the three-phase motor is shut down.

Images