Why is the motor reversed?

- Sep 20, 2018 -

Why is the motor reversed?

 

DC Rolling Shutter Door Motors.jpgThe rotor of the motor in operation of course has a rotational inertia. We cut off the current supply and let the motor stop. The motor will rotate for a while before stopping. This is the performance of the motor's rotational inertia. If we do not let the motor run directly in the reverse direction, the motor shaft will undergo a short deceleration process and then reverse start to normal speed. During this process, a large current surge occurs in the stator of the motor.


We know that the device that controls the operation of the motor is an AC contactor. For directly started motors, the AC contactor used in the category is AC-3, and the AC contactor used in the control circuit for jog, reverse brake and reversible starting is AC-4. The AC current contactor for the AC-3 use category has an overload current ratio of 8 times, while the AC contactor for the AC-4 use category has an overload ratio of 10 times.


Generally, in the motor vector control inverter, after the desired speed is stepped from a positive value to a negative value, after the speed loop PID controller, a reverse iq current is generated, thereby generating a negative torque, and the motor has inertia due to inertia. , will still rotate in the forward direction until the speed is 0, then start reverse acceleration. The length of the entire deceleration and reverse acceleration depends on the magnitude of the reverse torque generated by the current iq and the moment of inertia.