Motor braking system and permanent magnet motor

Abstract

The utility model relates to the field of motor control, in particular to a motor braking system and a permanent magnet motor. The motor braking system comprises a detection module, a braking control module and a motor driving module. The detection module is arranged on a power supply bus, a second end is connected with a first end of the brake control module, a second end of the brake control module is connected with a first end of the motor driving module, and a second end of the motor driving module is connected with a motor; the detection module collects a first voltage signal on a power supply bus in a motor braking state, generates an overvoltage signal when the voltage value of the first voltage signal is higher than a first preset signal, and transmits the overvoltage signal to the braking control module; the brake control module generates a discharge signal when receiving the overvoltage signal and transmits the discharge signal to the motor driving module; and the motor driving module stops motor braking when receiving the discharge signal. The motor is ensured not to generate overvoltage in a braking state by detecting the bus voltage, and the condition of braking failure is avoided.

Description

Technical Field

[0001] The utility model relates to the field of motor control, in particular to a motor braking system and a permanent magnet motor. Background Art

[0002] During the use of permanent magnet synchronous motors (such as permanent magnet fans), it is often encountered that the motor starts with reverse initial speed, in which case deceleration braking is required. In many cases, the bus capacitance is minimized and the braking resistor is eliminated for cost and volume considerations.

[0003] Traditional braking methods mainly adopt power generation deceleration braking or direct short-circuit braking. If the braking resistor is eliminated, direct short-circuit braking is likely to cause too much short-circuit current, which is not suitable for occasions with small motor internal resistance and high speed. During power generation deceleration braking, the motor works in the second quadrant power generation state. At this time, the motor kinetic energy is continuously converted into electrical energy, and the current flows from the fan to the drive bus. When the power generation power is significantly higher than the auxiliary source power, the bus will rise rapidly, causing overvoltage of the drive bus and braking failure.

[0004] The above contents are only used to assist in understanding the technical solution of the present utility model and do not constitute an admission that the above contents are prior art. Utility Model Content

[0005] The main purpose of the utility model is to provide a motor braking system and a permanent magnet motor, aiming to solve the technical problem in the prior art that a motor without a braking resistor may cause busbar overvoltage during deceleration braking.

[0006] To achieve the above object, the utility model provides a motor braking system, which includes: a detection module, a braking control module and a motor driving module;

[0007] The detection module is arranged on the power supply bus, and the second end is connected to the first end of the brake control module, the second end of the brake control module is connected to the first end of the motor drive module, and the second end of the motor drive module is connected to the motor;

[0008] The detection module is used to collect a first voltage signal on the power supply bus when the motor is in a braking state, generate an overvoltage signal when the voltage value of the first voltage signal is higher than the first preset signal, and transmit the overvoltage signal to the braking control module;

[0009] The brake control module is used to generate a discharge signal when receiving the overvoltage signal, and transmit the discharge signal to the motor drive module;

[0010] The motor driving module is used to stop motor braking when receiving the discharge signal.

[0011] Optionally, the detection module is further used to collect a first voltage signal on the power supply bus when the motor stops braking, and generate an undervoltage signal when the voltage value of the first voltage signal is lower than the second preset signal, and transmit the undervoltage signal to the brake control module;

[0012] The brake control module is further configured to generate a brake signal upon receiving the undervoltage signal, and transmit the brake signal to the motor drive module;

[0013] The motor driving module is further used to drive the motor to brake when receiving the braking signal.

[0014] Optionally, the detection module includes: a bus capacitor and a comparator;

[0015] The bus capacitor is arranged on the power supply bus and is connected to the input end of the comparator. The output end of the comparator is connected to the brake control module.

[0016] Optionally, the motor driving module includes: a feedback unit and a driving unit;

[0017] The first end of the drive unit is connected to the brake control module, and the second end of the drive unit is connected to the motor; the first end of the feedback unit is connected to the second end of the drive unit, and the second end of the feedback unit is connected to the brake control module;

[0018] The feedback unit is used to collect the three-phase signal of the motor operation, convert the three-phase signal into a first feedback signal, and transmit the first feedback signal to the brake control module;

[0019] The braking control module is further configured to drive the motor from a braking state to an electric state according to the first feedback signal when receiving the discharge signal.

[0020] Optionally, the feedback unit includes: a Clarke converter and a Park converter;

[0021] The input end of the Clarke converter is connected to the motor, the output end of the Clarke converter is connected to the input end of the Park converter, and the output end of the Park converter is connected to the brake control module.

[0022] Optionally, the driving unit includes: a Clarke inverter, a Park inverter and a three-phase full-bridge inverter;

[0023] The input end of the Park inverter is connected to the second end of the brake control module, the output end of the Park inverter is connected to the input end of the Clarke inverter, the output end of the Clarke inverter is connected to the input end of the three-phase full-bridge inverter, and the output end of the three-phase full-bridge inverter is connected to the motor.

[0024] Optionally, the feedback unit further includes: a position observer;

[0025] The input end of the position observer is connected to the output end of the Clarke converter, and the output end of the position observer is simultaneously connected to the Park converter and the Park inverter.

[0026] Optionally, the motor braking system further includes: a rectifier bridge;

[0027] The input end of the rectifier bridge is connected to the commercial power grid, and the output end of the rectifier bridge is connected to the detection module and the three-phase full-bridge inverter at the same time.

[0028] Optionally, the torque of the motor driven by the motor in a braking state when the motor driving module receives the braking signal is greater than the torque of the motor driven by the motor in an electric state when the motor driving module receives the discharge signal.

[0029] In addition, to achieve the above-mentioned purpose, the utility model also provides a permanent magnet motor, and the permanent magnet motor includes: the above-mentioned motor braking system.

[0030] The technical solution of the utility model proposes a motor braking system and a permanent magnet motor. The motor braking system includes: a detection module, a braking control module and a motor driving module; the detection module is arranged on the power supply bus, and the second end is connected to the first end of the braking control module, the second end of the braking control module is connected to the first end of the motor driving module, and the second end of the motor driving module is connected to the motor; the detection module is used to collect the first voltage signal on the power supply bus in the motor braking state, and generate an overvoltage signal when the voltage value of the first voltage signal is higher than the first preset signal, and transmit the overvoltage signal to the braking control module; the braking control module is used to generate a discharge signal when receiving the overvoltage signal, and transmit the discharge signal to the motor driving module; the motor driving module is used to stop the motor braking when receiving the discharge signal. By detecting the bus voltage, it is ensured that the motor will not be over-voltage in the braking state, avoiding the situation of braking failure, and then continue to brake after the bus voltage is reduced, and the average braking torque of the whole braking process is positive, so as to realize the intermittent braking of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0032] Figure 1 This is a functional module diagram of the first embodiment of the motor brake system of the utility model;

[0033] Figure 2 It is a structural schematic diagram of the second embodiment of the motor brake system of the utility model;

[0034] Figure 3 A current signal diagram output by a brake control module in the second embodiment of the motor brake system of the utility model;

[0035] Figure 4 This is a functional module diagram of the third embodiment of the motor brake system of the utility model;

[0036] Figure 5 It is a structural schematic diagram of the third embodiment of the motor brake system of the utility model;

[0037] Figure 6 It is the bus voltage of the permanent magnet motor in the braking state proposed by the utility model;

[0038] Figure 7 It is the torque of the permanent magnet motor in the braking state proposed by the utility model;

[0039] Figure 8 This is the deceleration curve of the permanent magnet motor in the braking state proposed by the utility model.

[0040] Description of Figure Numbers:

[0041]

[0042] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0043] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0045] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0046] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0047] Reference Figure 1 , Figure 1 The first embodiment of the motor brake system of the utility model is a functional module diagram. The utility model provides a first embodiment of the motor brake system.

[0048] In this embodiment, the motor brake system includes: a detection module 10, a brake control module 20 and a motor drive module 30. The detection module 10 is arranged on the power supply bus, and the second end of the detection module 10 is connected to the first end of the brake control module 20, the second end of the brake control module 20 is connected to the first end of the motor drive module 30, and the second end of the motor drive module 30 is connected to the motor.

[0049] It should be noted that the detection module 10 can collect the first voltage signal Vbus on the power supply bus when the motor is in a braking state, generate an overvoltage signal when the voltage value of the first voltage signal Vbus is higher than the first preset signal Vcomup, and transmit the overvoltage signal to the brake control module 20; the brake control module 20 can generate a discharge signal i when receiving the overvoltage signal disc , and the discharge signal i disc The motor driving module 30 can transmit the discharge signal idisc When the motor is stopped, brake.

[0050] The motor may be a synchronous motor using a permanent magnet (usually a rare earth permanent magnet material) as an excitation source. No external excitation is required because the permanent magnet itself provides a constant magnetic field. This allows the permanent magnet synchronous motor to have higher efficiency and dynamic response capabilities in constant speed and variable speed applications. The power supply bus may be a power transmission line composed of cables or wires that transmits city power from a distribution box to various electrical devices.

[0051] Furthermore, the first voltage signal may be a voltage amplitude signal on the power supply bus when the power supply bus supplies power to the permanent magnet motor.

[0052] The first preset signal may be a signal pre-set in the detection module for determining whether the voltage on the power supply bus is over-voltage. The coordinate system constructed using the speed and torque when the permanent magnet motor is running has four quadrants. For example, when the motor is in the second quadrant (i.e., the speed is negative and the torque is positive) during braking, the kinetic energy of the motor's rotation will be converted into electrical energy and flow to the power supply bus, causing the power supply bus to increase voltage or even over-voltage.

[0053] The overvoltage signal may be a comparison signal when the first voltage signal on the power supply bus acquired by the detection module exceeds the first preset signal. When an abnormal overvoltage occurs on the power supply bus, the braking of the motor may fail.

[0054] The discharge signal may be a signal generated by the brake control module to control the motor drive module to change the motor from a brake state to an electric state. The discharge signal may be a signal pre-set in the brake control module, or an adjustment signal generated according to the speed and torque of the motor.

[0055] It should be understood that when the motor is in the braking state, the above-mentioned power supply bus is over-voltage, and the over-voltage power supply bus is used to control the motor to enter the electric state, so as to reduce the bus voltage. At the same time, the braking torque of the braking process is positive to achieve braking of the motor.

[0056] It should be noted that the motor drive module can use field oriented control (FOC) to achieve precise control of the motor speed and torque by controlling the current and magnetic field direction of the permanent magnet motor. Space vector pulse width modulation (SVPWM) can also be used to control the phase current of the motor to achieve control of the motor speed. This is not limited in this embodiment.

[0057] This embodiment proposes a motor braking system, including: a detection module, a braking control module and a motor driving module; the detection module is arranged on the power supply bus, and the second end is connected to the first end of the braking control module, the second end of the braking control module is connected to the first end of the motor driving module, and the second end of the motor driving module is connected to the motor; the detection module is used to collect the first voltage signal on the power supply bus in the motor braking state, generate an overvoltage signal when the voltage value of the first voltage signal is higher than the first preset signal, and transmit the overvoltage signal to the braking control module; the braking control module is used to generate a discharge signal when receiving the overvoltage signal, and transmit the discharge signal to the motor driving module; the motor driving module is used to stop the motor braking when receiving the discharge signal. By detecting the bus voltage, it is ensured that the motor will not be over-voltage in the braking state to avoid the situation of braking failure.

[0058] Reference Figure 2 and Figure 3 , Figure 2 It is a structural schematic diagram of the second embodiment of the motor brake system of the utility model; Figure 3 This is a current signal diagram output by the brake control module in the second embodiment of the motor brake system of the utility model. Based on the first embodiment of the motor brake system mentioned above, the second embodiment of the motor brake system of the utility model is proposed.

[0059] In this embodiment, the detection module 10 is also used to collect the first voltage signal Vbus on the power supply bus when the motor stops braking, and generate an undervoltage signal when the voltage value of the first voltage signal Vbus is lower than the second preset signal Vcomdown, and transmit the undervoltage signal to the braking control module 20.

[0060] It should be noted that the second preset signal may be a signal pre-set in the detection module for determining whether the voltage on the power supply bus is reduced to a level that the motor can continue to brake. During the braking process, the permanent magnet motor enters the electric state, at which time the kinetic energy of the motor's rotation will consume the overvoltage electrical energy in the bus capacitor, causing the power supply bus to reduce voltage to ensure that the motor can continue to brake normally.

[0061] It should be understood that the undervoltage signal can be a comparison signal when the first voltage signal on the power supply bus collected by the detection module is lower than the second preset signal. When the voltage of the power supply bus is lower than the second preset signal, the permanent magnet motor can continue to brake and cause the voltage of the power supply bus to increase during the braking process without causing abnormal overvoltage.

[0062] Furthermore, the brake control module 20 is further configured to generate a brake signal i upon receiving the undervoltage signal.brake , and the braking signal i brake The motor drive module 30 is also used to receive the braking signal i brake The drive motor brakes.

[0063] It should be noted that the braking signal may be a signal generated by the braking control module to control the motor driving module to change the motor from the electric state to the braking state. The braking signal may be a signal pre-set in the braking control module, or an adjustment signal generated according to the speed and torque of the motor.

[0064] It should be understood that the torque of the motor driving module 30 when driving the motor in the braking state when receiving the braking signal is greater than the torque of the motor driving module 30 when driving the motor in the electric state when receiving the discharge signal. Only when the torque of the motor in the braking state is greater than the torque in the electric state, can the above-mentioned motor achieve the process of braking and speed reduction. For example: when the motor is running in the second quadrant, the rated speed is 1000rpm, the phase resistance is 1.2Ω, the rated voltage is 380V, the first preset signal is set to 610V, and the second preset signal is set to 600V. The motor enters the electric state when the power supply bus voltage exceeds 610V, and enters the braking state when the power supply bus voltage is lower than 600V. The average torque is 7N, and the motor speed is controlled to decrease to complete the braking control.

[0065] Further, the detection module 10 includes: a bus capacitor C1 and a comparator Q1;

[0066] The bus capacitor C1 is disposed on the power supply bus and is connected to the input end of the comparator Q1 . The output end of the comparator Q1 is connected to the brake control module 20 .

[0067] It should be noted that the input end of the comparator Q1 collects the voltage on the bus capacitor C1, that is, the first voltage signal, and compares it with the first preset signal and the second preset signal stored internally. When the first voltage signal is higher than the first preset signal, an overvoltage signal is generated, and when the first voltage signal is lower than the second preset signal, an undervoltage signal is generated.

[0068] In this embodiment, the detection module is also used to collect the first voltage signal on the power supply bus when the motor stops braking, and generate an undervoltage signal when the voltage value of the first voltage signal is lower than the second preset signal, and transmit the undervoltage signal to the brake control module; the brake control module is also used to generate a brake signal when receiving the undervoltage signal, and transmit the brake signal to the motor drive module; the motor drive module is also used to drive the motor to brake when receiving the brake signal. By detecting the bus voltage, it is ensured that the motor will not be over-voltage in the braking state, avoiding the situation of braking failure, and then continue to brake after the bus voltage is reduced. The average braking torque of the entire braking process is positive, and intermittent braking of the motor is achieved. The deceleration braking control of the motor can be achieved without using a brake resistor, which simplifies the motor structure and reduces the cost of the motor.

[0069] Reference Figure 4 and Figure 5 , Figure 4 This is a functional module diagram of the third embodiment of the motor brake system of the utility model; Figure 5 The third embodiment of the motor brake system of the present utility model is shown in FIG. Based on the above embodiments of the motor brake system, the third embodiment of the motor brake system of the present utility model is proposed.

[0070] In this embodiment, the motor drive module 30 includes: a feedback unit 301 and a drive unit 302; the first end of the drive unit 302 is connected to the brake control module 20, and the second end of the drive unit 302 is connected to the motor; the first end of the feedback unit 301 is connected to the second end of the drive unit 302, and the second end of the feedback unit 301 is connected to the brake control module 20.

[0071] It should be noted that the feedback unit is used to collect the three-phase signal of the motor operation, convert the three-phase signal into a first feedback signal, and transmit the first feedback signal to the brake control module; the brake control module is also used to drive the motor from the brake state to the electric state according to the first feedback signal when receiving the discharge signal. The brake control module is also used to drive the motor from the electric state to the brake state according to the first feedback signal when receiving the brake signal.

[0072] The three-phase signal may be a three-phase current signal (ie, Ia, Ib and Ic) for controlling the motor, and the rotational speed of the motor may be controlled by controlling each phase current of the motor.

[0073] The first feedback signal may be a feedback sampling signal for realizing closed-loop control of the permanent magnet motor. By receiving the first feedback signal, the motor drive module 30 may adjust the controller output according to the control error (i.e., the difference between the expected value and the actual value) to make it as close to the expected value as possible. The speed and torque of the motor are controlled according to the closed-loop control method between the initial state and the feedback state of the motor.

[0074] Furthermore, the feedback unit 301 includes: a Clarke converter Q2 and a Park converter Q3. The input end of the Clarke converter Q2 is connected to the motor, the output end of the Clarke converter Q2 is connected to the input end of the Park converter Q3, and the output end of the Park converter Q3 is connected to the brake control module 20.

[0075] It should be noted that the above-mentioned Clarke transformation is a coordinate transformation, which converts the signal in the three-phase AC power system from the abc three-phase coordinate system to the αβ coordinate system. In the Clarke transformation, the three-phase voltage or current can be expressed as components on two orthogonal axes (α axis and β axis) to simplify the analysis and control of the power system. The Clarke converter Q2 can be an electronic device capable of implementing the Clarke transformation, such as an embedded microcontroller (Microcontroller Unit, MCU) or a digital signal processor (Digital Signal Processor, DSP), which is not limited in this embodiment.

[0076] The above Park transformation can convert the signal in the αβ coordinate system into the signal in the motor dq axis coordinate system by matrix operation. The discharge signal generated by the brake control module 20 can be generated by setting the current on the q axis to be in negative phase with the motor rotation torque (i.e. setting the discharge current on the q axis to -i disc ), the braking signal generated by the braking control module 20 can be generated by setting the current on the q-axis to be in positive phase with the motor rotation torque (i.e. setting the braking current on the q-axis to i brake The Park inverter Q3 can be implemented by using the same or similar electronic device as the Clarke converter Q2. The d-axis current can be set to a current signal -i that is negative to the machine torque. dref , so that the motor can reduce the back electromotive force in the weak magnetic state and make the voltage value of the power supply bus rise more slowly.

[0077] Furthermore, the drive unit 302 includes: a Clarke inverter Q4, a Park inverter Q5 and a three-phase full-bridge inverter Q6; the input end of the Park inverter Q5 is connected to the second end of the brake control module, the output end of the Park inverter Q5 is connected to the input end of the Clarke inverter Q4, the output end of the Clarke inverter Q4 is connected to the input end of the three-phase full-bridge inverter, and the output end of the three-phase full-bridge inverter is connected to the motor.

[0078] It should be noted that the Park inversion process can be the inverse process of the above-mentioned Park transformation, that is, the signal of the motor dq axis coordinate system is converted into a signal in the αβ coordinate system by matrix operation. The Clarke inversion process is the inverse process of the above-mentioned Clarke transformation, that is, the signal in the αβ coordinate system is converted into a signal in the abc three-phase coordinate system. The Clarke inverter and Park inverter can implement the above-mentioned Clarke inversion process and Park inversion process through electronic devices such as DSP or MCU.

[0079] It should be understood that the three-phase full-bridge inverter Q6 can be an electronic device that converts input direct current into three-phase alternating current by controlling the on and off of the switch tube, and realizes the output control of the motor abc three-phase signal according to the output control of the Clarke inverter.

[0080] Furthermore, the feedback unit 301 further includes: a position observer Q7; an input end of the position observer Q7 is connected to an output end of the Clarke converter Q2, and an output end of the position observer Q7 is simultaneously connected to the Park converter Q3 and the Park inverter Q5.

[0081] It should be noted that the position observer can be an electronic device used to measure and estimate the position and speed of the rotor of a rotating motor. It can analyze the signal in the αβ coordinate system generated by the Clarke transformer to calculate the real-time speed and position of the motor rotor, thereby achieving precise control of the Park transformation.

[0082] Furthermore, the motor braking system further comprises: a rectifier bridge 40. The input end of the rectifier bridge 40 is connected to the mains power grid, and the output end of the rectifier bridge 40 is connected to the detection module 10 and the three-phase full-bridge inverter Q6 at the same time.

[0083] It should be noted that the rectifier bridge can be a circuit or device that converts AC power from the mains power grid into DC power for supplying the motor, for example, it can be composed of an H-bridge circuit composed of field effect transistors or a diode bridge circuit.

[0084] This embodiment converts the three-phase signal of the driving motor into a current signal of the dq coordinate system, and sets the q-axis current through the braking control module, thereby generating a discharge signal and a braking signal to control the motor braking process. By detecting the bus voltage, it is ensured that the motor will not be over-voltage in the braking state, avoiding the situation of braking failure, and then continuing to brake after the bus voltage is reduced. The average braking torque of the entire braking process is positive, realizing intermittent braking of the motor. The deceleration braking control of the motor can be achieved without using a braking resistor, simplifying the motor structure and reducing the cost of the motor.

[0085] In addition, the embodiment of the present invention also provides a permanent magnet motor, which includes the above-mentioned motor braking system. Figure 6 , Figure 7 and Figure 8 , Figure 6 It is the bus voltage of the permanent magnet motor in the braking state proposed by the utility model; Figure 7 It is the torque of the permanent magnet motor in the braking state proposed by the utility model; Figure 8 This is the deceleration curve of the permanent magnet motor in the braking state proposed by the utility model.

[0086] It should be noted that, taking a 2.2kw motor as an example, the rated speed of the motor is 1000rpm, the three-phase resistance is 1.2Ω, the rated voltage is 380V, the bus capacitor is 15uf, the auxiliary source capacitor is 60uf, and the motor's moment of inertia is 0.2kg*m 2 , set the bus voltage to exceed 610V and drive the motor to enter the electric state, and switch to the braking state when it is lower than 600V. The bus voltage is controlled to fluctuate between 580-690V. Figure 6 ; The average torque is 7N, refer to Figure 7 , the speed is reduced from -450rpm to -350rpm, refer to Figure 8 .

[0087] Since the detection device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0088] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A motor braking system, characterized in that: The motor braking system comprises: a detection module, a braking control module and a motor driving module; The detection module is arranged on the power supply bus, and the second end is connected to the first end of the brake control module, the second end of the brake control module is connected to the first end of the motor drive module, and the second end of the motor drive module is connected to the motor; The detection module is used to collect a first voltage signal on the power supply bus when the motor is in a braking state, generate an overvoltage signal when the voltage value of the first voltage signal is higher than a first preset signal, and transmit the overvoltage signal to the braking control module; The brake control module is used to generate a discharge signal when receiving the overvoltage signal, and transmit the discharge signal to the motor drive module; The motor driving module is used to stop motor braking when receiving the discharge signal.

2. The motor brake system according to claim 1, characterized in that: The detection module is also used to collect a first voltage signal on the power supply bus when the motor stops braking, and generate an undervoltage signal when the voltage value of the first voltage signal is lower than the second preset signal, and transmit the undervoltage signal to the brake control module; The brake control module is further configured to generate a brake signal upon receiving the undervoltage signal, and transmit the brake signal to the motor drive module; The motor driving module is further used to drive the motor to brake when receiving the braking signal.

3. The motor brake system according to claim 2, characterized in that: The detection module includes: a bus capacitor and a comparator; The bus capacitor is arranged on the power supply bus and is connected to the input end of the comparator. The output end of the comparator is connected to the brake control module.

4. The motor brake system according to claim 1, characterized in that: The motor driving module comprises: a feedback unit and a driving unit; The first end of the drive unit is connected to the brake control module, and the second end of the drive unit is connected to the motor; the first end of the feedback unit is connected to the second end of the drive unit, and the second end of the feedback unit is connected to the brake control module; The feedback unit is used to collect the three-phase signal of the motor operation, convert the three-phase signal into a first feedback signal, and transmit the first feedback signal to the brake control module; The braking control module is further configured to drive the motor from a braking state to an electric state according to the first feedback signal when receiving the discharge signal.

5. The motor brake system according to claim 4, characterized in that: The feedback unit includes: a Clarke converter and a Park converter; The input end of the Clarke converter is connected to the motor, the output end of the Clarke converter is connected to the input end of the Park converter, and the output end of the Park converter is connected to the brake control module.

6. The motor brake system according to claim 5, characterized in that: The drive unit includes: a Clarke inverter, a Park inverter and a three-phase full-bridge inverter; The input end of the Park inverter is connected to the second end of the brake control module, the output end of the Park inverter is connected to the input end of the Clarke inverter, the output end of the Clarke inverter is connected to the input end of the three-phase full-bridge inverter, and the output end of the three-phase full-bridge inverter is connected to the motor.

7. The motor brake system according to claim 6, characterized in that: The feedback unit further includes: a position observer; The input end of the position observer is connected to the output end of the Clarke converter, and the output end of the position observer is simultaneously connected to the Park converter and the Park inverter.

8. The motor brake system according to claim 7, characterized in that: The motor braking system further includes: a rectifier bridge; The input end of the rectifier bridge is connected to the commercial power grid, and the output end of the rectifier bridge is connected to the detection module and the three-phase full-bridge inverter at the same time.

9. The motor brake system according to claim 2, characterized in that: The torque when the motor driving module drives the motor in a braking state when receiving the braking signal is greater than the torque when the motor driving module drives the motor in an electric state when receiving the discharge signal.

10. A permanent magnet motor, characterized in that: The permanent magnet motor comprises: a motor braking system as claimed in any one of claims 1 to 9.

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