Permanent magnet synchronous outer rotor motors are widely used in unmanned delivery and other fields due to their simple structure, easy maintenance, high precision, large load, and stable low-speed operation. However, when the motor is running too fast or stops suddenly or quickly, it will generate back electromotive force, which will affect the performance and stability of the motor. This article will explore the causes of the motor back electromotive force and its treatment methods.
Back EMF is an important physical phenomenon in the operation of motors. When a permanent magnet synchronous external rotor motor rotates, the current in its stator coil generates an induced EMF in the magnetic field. The direction of this induced EMF is opposite to the direction of the power supply EMF, so it is called back EMF. The existence of back EMF will cause the motor speed to drop, the torque to decrease, and even cause motor stall, vibration and other faults.
To deal with the back EMF problem of the motor, several approaches can be taken:
1. Add a brake resistor. The main function of the brake resistor is to convert the regenerative electrical energy generated when the motor is decelerating or braking, thereby protecting the motor and its control system. Choose an appropriate resistance value: Determine the resistance value of the brake resistor based on the rated power of the motor, the bus voltage during braking, and the required braking torque to ensure that it can meet the braking requirements without causing the resistor to overheat.
2. Optimize PWM control strategy: By accurately adjusting the duty cycle and frequency of the PWM signal, accurate control of the motor current and voltage can be achieved. This can not only effectively suppress the influence of back electromotive force, but also improve the efficiency and stability of the motor.
3. Closed-loop control: The current, voltage, speed and other parameters of the motor are monitored in real time through sensors, and these parameters are fed back to the control system. The control system dynamically adjusts the drive signal of the motor based on this feedback information to achieve real-time monitoring and compensation of back electromotive force.
4. Optimize the magnetic circuit structure: Rationally arrange the shape, size and position of the permanent magnet to make full use of the magnetic field and reduce magnetic resistance loss.
5. Improve winding design: Design reasonable number of winding turns, wire cross-sectional area and distribution to reduce resistance and leakage inductance and improve the response speed and efficiency of the motor.
In summary, through optimization at the circuit level and improvement of the motor body, we can effectively deal with the back EMF problem of the permanent magnet synchronous outer rotor motor. This can not only improve the performance and stability of the motor, but also reduce energy consumption and extend the service life of the motor. In practical applications, we need to choose the appropriate treatment method according to specific needs and conditions to achieve the best effect.
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