Motor system control has become an irreversible trend!
One company purchased relatively advanced equipment, integrating automation and intelligence. When equipment is abnormal, equipment manufacturers use remote control to check and eliminate problems. Intelligent control overcomes physical distance. problem.
The intelligent control of the equipment brings opportunities and challenges to the motor manufacturing enterprises, especially the fully automatic processing production line. More actions require the coordination of the control system, and the matching motor is effectively integrated with the control system. It is a Very critical issue.
In order to avoid the mismatch between the motor and the supporting equipment, many motor manufacturers will select the appropriate supporting system through the necessary test items. At present, the most common is the purchase or supply of inverters and motors. Especially for the development of high-efficiency products, many motor manufacturers have tried to move from single-machine energy saving to system energy-saving. The further development of large-scale automation and assembly line equipment has effectively promoted the intelligent and systematic development of electric motors.
Motor control introduction
Motor control refers to the control of starting, accelerating, running, decelerating and stopping the motor. There are different requirements and purposes depending on the type of motor and the use of the motor. For the motor, through the motor control, the motor achieves fast start, fast response, high efficiency, high torque output and high overload capability.
1. motor speed control
Motor speed control methods include series resistance speed regulation, frequency conversion speed regulation, variable pole speed regulation and vector control, and direct torque control.
The series resistance speed regulation is mainly used for asynchronous motors, and the speed regulation range is limited by the maximum torque of the motor.
The frequency conversion speed regulation is applicable to the induction motor, and the speed adjustment is achieved by adjusting the synchronous speed.
The pole-changing speed produces a speed of 1/2, 1/3... by changing the number of poles of the motor.
Vector control technology is to decouple the excitation winding and armature winding of the motor, so that the control induction motor is the same as the control DC motor. By adjusting the excitation and armature currents of the motor separately, the torque, rotation speed, back electromotive force, etc. of the motor are controlled.
Direct torque control directly controls the stator flux space vector and electromagnetic torque, and has the ability to respond quickly.
2. motor start control
● Buck start. It mainly includes autotransformer startup, star-delta change start, and variable voltage start. When the asynchronous motor starts, the rotor is in a static state, the starting current is large, and the starting current can be reduced by the step-down starting. Since the starting torque of the asynchronous motor is proportional to the square of the voltage, it is necessary to ensure that the motor has a certain starting capability for the step-down starting.
● Increase the rotor loop start. Suitable for wound rotors, deep groove rotors and double cage rotors. This method cannot be used for squirrel cage rotors.
● Start of single-phase asynchronous motor. Including capacitor start, resistor start, PTC start, hood start and so on. Since the single-phase winding of the induction motor cannot generate a rotating magnetic potential when the rotor is stationary, only the asynchronous motor of the single-phase winding cannot be self-starting. In this regard, it is necessary to mount an auxiliary winding 90° to the main winding on the single-phase asynchronous motor. This winding is mainly used for starting the motor. When the motor is started, the winding can be cut off or used for motor operation.
● Synchronous motor starts. Since the synchronous motor rotor rotates at a synchronous speed, there is no slip. When the speed of the rotor differs greatly from the synchronous speed, an out-of-step phenomenon will occur and it will not be self-starting. The starting mode of the synchronous motor includes variable frequency starting, asynchronous motor driving start, linear motor self starting.
● Variable frequency start. When the frequency conversion starts, the rate of change of the starting voltage frequency is usually set. When the motor runs to 60% to 80% of the rated speed, the rated frequency is added to the motor and directly brought into synchronization. Asynchronous motors drive similar start-ups.
● Linear motor starts. The rotor structure is a permanent magnet + squirrel cage, and the squirrel cage is used for the starting process. When the motor runs to synchronous speed, the squirrel cage no longer generates electromagnetic torque.
Reprinted from the network