The speed control system of permanent magnet synchronous motor mainly relies on changing the input voltage and current of the motor to adjust its speed. By adjusting the frequency and amplitude of the input current, the speed and torque of the motor can be controlled.
Variable frequency speed control is a common method of permanent magnet synchronous motor speed control. It uses a frequency converter to convert fixed frequency AC into variable frequency AC to drive the motor. By changing the power input frequency, the motor speed can be adjusted steplessly. Variable frequency speed control has good dynamic response performance and can achieve smooth speed changes.
Variable voltage speed control is another speed control method that adjusts the speed by changing the terminal voltage of the motor. This usually uses a transformer to adjust the voltage input to the motor. Although variable voltage speed control can achieve a wider speed control range, its dynamic response performance is relatively poor.
Vector control is an advanced speed control strategy that controls the speed by adjusting the vector relationship between the current and voltage of the motor. In a permanent magnet synchronous motor, the three-phase voltage generated by the voltage source inverter can be decomposed into an excitation component and a torque component. By adjusting the amplitude and phase of these two components, the torque and speed of the motor can be precisely controlled.
Direct torque control is another speed regulation method that directly controls the torque of the motor to achieve speed regulation. By adjusting the input current of the motor, the torque can be changed quickly, thereby achieving a fast speed response.
In practical applications, a speed controller is usually used to measure the actual speed of the motor and compare it with the expected speed. If the actual speed does not match the expected speed, the speed controller generates a corresponding command signal to adjust the input current or voltage of the motor, thereby achieving precise control of the motor speed.
In addition to the above methods, there are some other speed regulation methods, such as slip speed regulation and switched reluctance speed regulation. These methods have their own characteristics, and the appropriate speed regulation strategy can be selected according to the specific application scenario and requirements.
