Three-phase winding electromagnetic braking system and method for brushless direct current motor

Abstract

This invention discloses a three-phase winding electromagnetic braking system for a brushless DC motor, comprising a DC power supply, a driver, a brake, three position sensors, and three sets of coils. The DC power supply supplies power to phases A, B, and C of the three-phase windings of the brushless DC motor through the driver. The three position sensors are used to monitor the rotor position of the brushless DC motor and are connected to the driver. The three sets of coils are connected in a star configuration, with their tail ends shorted together and connected to the negative terminal of the driver power supply. The starting ends of the three sets of coils are defined as phases A1, B1, and C1, respectively, and phases A1, B1, and C1 are connected to phases A, B, and C of the brushless DC motor, respectively. This invention achieves automatic unlocking upon motor start-up and automatic braking upon motor stop, possessing comprehensive technical advantages such as fast response, stable braking, long lifespan, and high safety. It is a preferred solution for "high-performance braking" in brushless DC motors and can be widely applied in fields with high requirements for braking safety and stability.

Description

Technical Field

[0001] This invention belongs to the field of mechanical manufacturing technology, specifically relating to an electromagnetic braking system and method for a three-phase winding of a brushless DC motor. Background Technology

[0002] An electromagnetic brake is a mechanical component that stops or slows down moving parts in a machine. It is commonly known as a brake or decelerator. A brake mainly consists of a brake frame, brake components, and an operating device. Some brakes also have an automatic adjustment device for the brake component clearance. To reduce braking torque and structural dimensions, brakes are usually mounted on the high-speed shaft of the equipment. However, for large equipment with high safety requirements (such as mine hoists and elevators), brakes should be mounted on the low-speed shaft closer to the working part of the equipment.

[0003] Electromagnetic braking is an ideal automated actuator in modern industry, primarily used in mechanical transmission systems to transmit power and control motion. It boasts advantages such as compact structure, simple operation, sensitive response, reliable use, and ease of remote control. It is mainly used in conjunction with a series of motors. It is widely applied in machinery used in metallurgy, construction, chemical industry, food processing, machine tools, stage equipment, elevators, ships, packaging, and other applications, as well as in emergency braking situations (for safety).

[0004] Currently, brushless DC motors typically use electromagnetic brakes for braking. However, existing electromagnetic brakes have several drawbacks, such as short release and closing times, large and unstable closing force impacts, and, as electrical devices, requiring dedicated power supplies for control regardless of whether they are powered by AC or DC. This makes control and maintenance complex and difficult when the power supply voltage fluctuates significantly. Therefore, there is an urgent need to optimize and improve the braking methods of electromagnetic brakes for brushless DC motors. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this invention provides a scientifically sound, easily controllable, and smoothly braking three-phase winding electromagnetic braking system and method for brushless DC motors.

[0006] To solve the above technical problems, the present invention adopts the following technical solution: a three-phase winding electromagnetic braking system for a brushless DC motor, comprising a DC power supply, a driver, a brake, three position sensors, and three sets of coils. The DC power supply supplies power to phases A, B, and C of the three-phase windings of the brushless DC motor through the driver. The three position sensors are used to monitor the rotor position of the brushless DC motor. The signal output terminals of the three position sensors are connected to the signal input terminals of the driver. The three sets of coils are connected in a star configuration. The tail ends of the three sets of coils are shorted together (GND) and connected to the negative terminal of the driver power supply. The starting ends of the three sets of coils are defined as phases A1, B1, and C1, respectively. Phases A1, B1, and C1 are connected to phases A, B, and C of the brushless DC motor, respectively.

[0007] The driver includes a power conversion unit and a control circuit. The power conversion unit consists of a converter composed of six power transistors V1-V6 and six freewheeling diodes D1-D6. The control circuit is a logic control unit.

[0008] The method for electromagnetic braking of three-phase windings of a brushless DC motor, implemented using a three-phase electromagnetic braking system for a brushless DC motor, includes the following steps: S0. The brushless DC motor starts. The three phases of the brushless DC motor are energized sequentially in six states: A+C-, A+B-, C+B-, C+A-, B+A-, and B+C-. The three sets of coils connected to the brake are energized sequentially to establish a magnetic field. The brake is engaged and unlocked, and the brushless DC motor operates normally. S1. Trigger braking command; control circuit receives and parses the command. S2, The control circuit outputs electrical control signals; S3. Electric braking start-up - the converter reconfigures the stator winding circuit, and the motor and brake three-phase windings are de-energized one after another (generally, the brake has a large inductance and a long de-energization delay). S4. Induced current is generated, forming a reverse electromagnetic torque; S5. Electric braking consumes energy and reduces speed rapidly; S6, Mechanical brake activation—The three sets of coils connected to the brake are de-energized; S7. Mechanical brake engagement, applying mechanical braking torque; S8, coordinated stop and lock, braking completed.

[0009] The braking trigger command in step S1 includes, but is not limited to: manually pressing the stop button, equipment positioning signal, and emergency stop command; after the braking command is triggered, the control circuit in the driver receives the signal, immediately stops outputting the "commutation control signal for normal motor operation", and starts the "braking mode logic" at the same time; at the same time, the three position sensors: H1 / H2 / H3 continuously feed back the real-time rotor speed and position to the control circuit to provide speed reference for the braking process.

[0010] In step S2, the two core control signals include: the first electrical braking signal: outputting a power transistor turn-on command to the converter in "energy consumption braking mode"; and the second mechanical braking signal: outputting a "power-off command" to the three coil power supply circuits of the electromagnetic brake to cut off the coil power supply. The two signals are issued synchronously to ensure that the two braking methods are connected without delay.

[0011] In step S3, after receiving the command, the converter changes the conduction logic of power transistors V1 to V6: it controls the upper and lower power transistors V1+V4, V3+V6, and V5+V2 on the same bridge arm to conduct sequentially or simultaneously; the stator three-phase windings A, B, and C form a three-phase closed loop through the conducting power transistors; the freewheeling diodes D1 to D6 in the loop play the role of "clamping voltage and protecting power transistors" to avoid damage to the devices due to excessive induced current.

[0012] Step S4 specifically includes the following process: The motor rotor continues to rotate due to inertia, and the magnetic field generated by the permanent magnet on the rotor will continuously cut the conductor of the stator winding; induced back electromotive force is generated, and the back electromotive force drives the formation of braking current in the closed stator winding circuit; the braking current is subjected to electromagnetic force in the magnetic field of the permanent magnet rotor, and according to the left-hand rule, the direction of the electromagnetic torque formed by this electromagnetic force is opposite to the direction of rotor rotation, that is, braking torque.

[0013] The specific process of step S8 is as follows: the rotor speed has been reduced to a low level due to electric braking, and the mechanical braking torque further hinders the rotor rotation, quickly consuming the remaining inertial kinetic energy; when the rotor kinetic energy is completely consumed, the motor speed drops to 0; after the motor stops, the mechanical braking torque continues to exist, locking the main shaft; the control circuit confirms that the rotor is completely stationary through the position sensor, and the braking process ends.

[0014] By adopting the above technical solution, compared with the prior art, the present invention has the following technical effects (significant progress): 1) Traditional electromagnetic brakes require a separate power supply from the motor driver. If a power failure occurs, there is a risk of malfunction. This invention connects the electromagnetic brake and the motor in parallel across three phases, eliminating the need for a separate power supply from the controller. The brake unlocks when the motor is working and brakes when the motor stops, eliminating the risk of malfunction.

[0015] 2) Fast braking response, high deceleration efficiency, and short stopping time. The total time from triggering the braking command to the motor coming to a complete stop is much shorter than that of single mechanical braking or single electric braking. Electric braking provides "instantaneous force," and after the braking command is issued, the converter instantly reconstructs the closed circuit of the winding, and the reverse electromagnetic torque quickly consumes the rotor's kinetic energy, causing the speed to drop significantly in a short time (without waiting for the mechanical parts to engage). Mechanical braking provides "tail-end force replenishment," and when the speed drops to a low level, the mechanical brake engages quickly, completely consuming the remaining inertial kinetic energy and avoiding "slow deceleration and trailing stop."

[0016] 3) Smooth braking without impact, protecting the motor and load. There is no severe vibration or significant impact load during braking, and the mechanical stress on the motor shaft and load mechanism is small. The electric braking first buffers and decelerates, and the reverse electromagnetic torque is gradual (changing gradually as the speed decreases), avoiding the instantaneous impact caused by the hard friction of single mechanical braking. The smooth and close mechanical braking extends the service life of the motor bearings and load mechanism, and reduces the frequency of equipment maintenance.

[0017] 4) Braking components experience less wear and have a longer service life. Electric braking undertakes the "main energy consumption task," with more than 80% of the rotor's kinetic energy being consumed as heat through the electrical circuit rather than relying on mechanical friction. Mechanical braking only undertakes the "remaining kinetic energy consumption and locking," and the contact speed during braking is low speed (rather than high-speed hard friction), which greatly reduces the friction intensity between the friction pads and the armature.

[0018] 5) Highly adaptable, compatible with different load and speed scenarios. The braking intensity can be flexibly adjusted according to the load size and initial speed, achieving both "rapid emergency stop" and "slow and smooth stop". The electrical braking intensity is adjustable, and the control circuit can adjust the magnitude of the induced current in the stator winding by changing the conduction time and conduction logic of the converter power transistor, thereby changing the intensity of the reverse electromagnetic torque.

[0019] In summary, the essence of the synergistic braking method adopted in this invention is that electrical braking is responsible for "efficient deceleration" and mechanical braking is responsible for "reliable locking". Ultimately, it achieves comprehensive technical advantages of "fast response, stable braking, long service life and high safety". It is the preferred solution for "high-performance braking" in brushless DC motors and can be widely used in fields with high requirements for braking safety and stability, such as industrial automation, transportation and engineering machinery. Attached Figure Description

[0020] Figure 1 This is a block diagram illustrating the working principle of the brushless DC motor of the present invention; Figure 2 This is a schematic diagram of the braking principle of the present invention; Figure 3This is a schematic diagram showing the six operating states of the three sets of coils connected to the brake, and the direction of the magnetic field. Detailed Implementation

[0021] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0022] like Figures 1-3 As shown, the three-phase winding electromagnetic braking system of the brushless DC motor of the present invention includes a DC power supply 1, a driver 2, a brake 3, three position sensors 4, and three sets of coils 7. The DC power supply 1 supplies power to the three-phase windings A, B, and C of the brushless DC motor 5 through the driver 2. The three position sensors 4 are used to monitor the rotor position of the brushless DC motor 5. The signal output terminals of the three position sensors 4 are connected to the signal input terminals of the driver 2. The three sets of coils 7 are connected in a star configuration. The tail ends of the three sets of coils 7 are shorted together (GND) and connected to the negative terminal of the power supply of the driver 2. The starting ends of the three sets of coils 7 are defined as phases A1, B1, and C1, respectively. Phases A1, B1, and C1 are connected to phases A, B, and C of the brushless DC motor 5, respectively.

[0023] The driver 2 includes a power conversion unit and a control circuit 6. The power conversion unit includes a converter consisting of six power transistors V1-V6 and six freewheeling diodes D1-D6. The control circuit 6 is a logic control unit.

[0024] The working process of a brushless DC motor is as follows: (1) Power supply and signal acquisition: DC power supply 1 supplies power to driver 2, and three position sensors 4 (H1 / H2 / H3) detect the position of permanent magnet rotor in real time and transmit the signal to the control circuit 6 of driver 2; (2) Converter commutation control: The control circuit 6 drives the power transistors (V1 to V6) of the converter to turn on or off sequentially according to a specific logic based on the position signal; (3) Stator winding excitation: The converter converts DC power into alternating current and supplies it to the three-phase stator windings A / B / C of the brushless DC motor 5, so that the three-phase windings generate a rotating magnetic field. (4) The motor runs continuously: the rotating magnetic field interacts with the magnetic field of the permanent magnet rotor, causing the rotor to rotate; after the rotor position changes, the position sensor 4 feeds back the signal again, and the control circuit 6 repeats the commutation logic to maintain the continuous operation of the brushless DC motor 6.

[0025] The electromagnetic braking method for the three-phase windings of a brushless DC motor includes the following steps: S0. The brushless DC motor starts. The three phases of the brushless DC motor are energized sequentially in six states: A+C-, A+B-, C+B-, C+A-, B+A-, and B+C-. The three sets of coils 7 connected to the brake 3 are energized sequentially to establish a magnetic field. The brake 3 is engaged and unlocked, and the brushless DC motor operates normally.

[0026] S1, trigger braking command, control circuit 6 receives and parses the command; S2, Control Circuit 6 outputs electrical control signals; S3, Electric Braking Start-up—The converter reconfigures the stator winding circuit, and the motor and brake 3 three-phase windings are de-energized one after another (generally, the inductance of brake 3 is large and the de-energization delay is long). S4. Induced current is generated, forming a reverse electromagnetic torque; S5. Electric braking consumes energy and reduces speed rapidly; S6, Mechanical brake activation—the three sets of coils 7 connected to brake 3 are de-energized; S7. Mechanical brake engagement, applying mechanical braking torque; S8, coordinated stop and lock, braking completed.

[0027] The braking trigger command in step S1 includes, but is not limited to: manually pressing the stop button, equipment positioning signal, and emergency stop command; after the braking command is triggered, the control circuit 6 in the driver 2 receives the signal, immediately stops outputting the "commutation control signal for normal motor operation", and starts the "braking mode logic" at the same time; at the same time, the three position sensors 4: H1 / H2 / H3 continuously feed back the real-time rotor speed and position to the control circuit 6 to provide speed reference for the braking process.

[0028] In step S2, the two core control signals include: the first electrical braking signal: outputting a power transistor turn-on command for "energy consumption braking mode" to the converter; the second mechanical braking signal: outputting a "power-off command" to the power supply circuit of the three sets of coils 7 of the electromagnetic brake 3 to cut off the power supply to the coils 7. The two signals are issued synchronously to ensure that the two braking methods are connected without delay.

[0029] In step S3, after receiving the command, the converter changes the conduction logic of power transistors V1 to V6: it controls the upper and lower power transistors V1+V4, V3+V6, and V5+V2 on the same bridge arm to conduct sequentially or simultaneously; the stator three-phase windings A, B, and C form a three-phase closed loop through the conducting power transistors; the freewheeling diodes D1 to D6 in the loop play the role of "clamping voltage and protecting power transistors" to avoid damage to the devices due to excessive induced current.

[0030] Step S4 specifically includes the following process: The motor rotor continues to rotate due to inertia, and the magnetic field generated by the permanent magnet on the rotor will continuously cut the conductor of the stator winding; induced back electromotive force is generated, and the back electromotive force drives the formation of braking current in the closed stator winding circuit; the braking current is subjected to electromagnetic force in the magnetic field of the permanent magnet rotor, and according to the left-hand rule, the direction of the electromagnetic torque formed by this electromagnetic force is opposite to the direction of rotor rotation, that is, braking torque.

[0031] The specific process of step S8 is as follows: the rotor speed has been reduced to a low level due to electric braking, and the mechanical braking torque further hinders the rotor rotation, quickly consuming the remaining inertial kinetic energy; when the rotor kinetic energy is completely consumed, the motor speed drops to 0; after the motor stops, the mechanical braking torque continues to exist, locking the main shaft; the control circuit 6 confirms that the rotor is completely stationary through the position sensor 4, and the braking process ends.

[0032] The above embodiments illustrate the basic principles and features of the present invention, but are merely preferred embodiments and are not limited to these embodiments. Those skilled in the art, inspired by this patent, can make many modifications and improvements without departing from the spirit and scope of the claims, all of which fall within the scope of protection of the present invention. Therefore, the scope of this patent and its protection should be determined by the appended claims.

Claims

1. A three-phase winding electromagnetic braking system for a brushless DC motor, characterized in that: It includes a DC power supply, a driver, a brake, three position sensors, and three sets of coils. The DC power supply supplies power to the three-phase windings A, B, and C of the brushless DC motor through the driver. The three position sensors are used to monitor the rotor position of the brushless DC motor. The signal output terminals of the three position sensors are connected to the signal input terminals of the driver. The three sets of coils are connected in a star configuration. The tail ends of the three sets of coils are shorted together (GND) and connected to the negative terminal of the driver power supply. The starting ends of the three sets of coils are defined as phases A1, B1, and C1, respectively. Phases A1, B1, and C1 are connected to phases A, B, and C of the brushless DC motor, respectively.

2. The three-phase winding electromagnetic braking system for a brushless DC motor according to claim 1, characterized in that: The driver includes a power conversion unit and a control circuit. The power conversion unit consists of a converter composed of six power transistors V1-V6 and six freewheeling diodes D1-D6. The control circuit is a logic control unit.

3. A method for electromagnetic braking of a three-phase winding of a brushless DC motor, implemented using the three-phase winding electromagnetic braking system for a brushless DC motor as described in claim 2, characterized in that: Includes the following steps: S0. The brushless DC motor starts. The three phases of the brushless DC motor are energized sequentially in six states: A+C-, A+B-, C+B-, C+A-, B+A-, and B+C-. The three sets of coils connected to the brake are energized sequentially to establish a magnetic field. The brake is engaged and unlocked, and the brushless DC motor operates normally. S1. Trigger braking command; control circuit receives and parses the command. S2, The control circuit outputs electrical control signals; S3. Electric braking start-up - the converter reconfigures the stator winding circuit, and the motor and brake three-phase windings are de-energized one after another. Generally, the brake has a large inductance and a long de-energization delay. S4. Induced current is generated, forming a reverse electromagnetic torque; S5. Electric braking consumes energy and reduces speed rapidly; S6, Mechanical brake activation—The three sets of coils connected to the brake are de-energized; S7. Mechanical brake engagement, applying mechanical braking torque; S8, coordinated stop and lock, braking completed.

4. The electromagnetic braking method for the three-phase windings of a brushless DC motor according to claim 3, characterized in that: The braking trigger command in step S1 includes, but is not limited to: manually pressing the stop button, equipment positioning signal, and emergency stop command; after the braking command is triggered, the control circuit in the driver receives the signal, immediately stops outputting the "commutation control signal for normal motor operation", and starts the "braking mode logic" at the same time; at the same time, the three position sensors: H1 / H2 / H3 continuously feed back the real-time rotor speed and position to the control circuit to provide speed reference for the braking process.

5. The electromagnetic braking method for the three-phase windings of a brushless DC motor according to claim 4, characterized in that: The electrical control signals in step S2 include: the first electrical braking signal: outputting a power transistor turn-on command for "energy consumption braking mode" to the converter; the second mechanical braking signal: outputting a "power-off command" to the three coil power supply circuits of the electromagnetic brake to cut off the coil power supply; the two signals are issued synchronously to ensure that the two braking methods are connected without delay.

6. The electromagnetic braking method for the three-phase windings of a brushless DC motor according to claim 5, characterized in that: In step S3, after receiving the command, the converter changes the conduction logic of power transistors V1 to V6: it controls the upper and lower power transistors V1+V4, V3+V6, and V5+V2 on the same bridge arm to conduct sequentially or simultaneously; the stator three-phase windings A, B, and C form a three-phase closed loop through the conducting power transistors; the freewheeling diodes D1 to D6 in the loop play the role of "clamping voltage and protecting power transistors" to avoid damage to the devices due to excessive induced current.

7. The electromagnetic braking method for the three-phase windings of a brushless DC motor according to claim 6, characterized in that: Step S4 specifically includes the following process: the motor rotor continues to rotate due to inertia, and the magnetic field generated by the permanent magnet on the rotor will continuously cut the conductors of the stator winding. An induced back electromotive force is generated, which drives the formation of a braking current in the closed stator winding circuit. The braking current is subjected to electromagnetic force in the magnetic field of the permanent magnet rotor. According to the left-hand rule, the direction of the electromagnetic torque formed by this electromagnetic force is opposite to the direction of rotor rotation, which is the braking torque.

8. The electromagnetic braking method for the three-phase windings of a brushless DC motor according to claim 7, characterized in that: The specific process of step S8 is as follows: the rotor speed has been reduced to a low level due to electric braking, and the mechanical braking torque further hinders the rotor rotation, quickly consuming the remaining inertial kinetic energy; when the rotor kinetic energy is completely consumed, the motor speed drops to 0; after the motor stops, the mechanical braking torque continues to exist, locking the main shaft; the control circuit confirms that the rotor is completely stationary through the position sensor, and the braking process ends.

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