Control loop reaction when high speed


Thread Starter


Hi everybody,

I have a servo drive and synch. motor. We all know that the motor torque will derate at higher speed. My question here is: what will happen to the control loop and reaction of servo motor when the motor is running at the highest speed and the torque left in the motor is 35%. The torque require to push the object will require the motor to run at 50% speed and 100% torque of the motor.

1) What will happen to the motor when it hits this load?

and after finish pushing the load the motor will go back to zero torque without any load to push.

2) What will happen to the servo motor after such drastic change in torque load?

For a normal induction motor, the motor will automatically slow down until the torque is require by the load.

Hope to hear from someone.
Because this is a servo loop with feedback, the system will only demand from the motor wharever is required to keep up with the command, from both a speed and torque point of view. When the command asks for more than the motor can deliver, the error (command minus feedback) will continie to get larger until an excess error alarm is activated and the system shuts down.

I have a free booklet titled "Servo Basics for the Layman" that describes the fundamentals of servos. Send me an email and I'll email back the booklet.

Good luck.
Tom Bullock
[email protected].
You must review SOA of your motor from Speed - Torque curve. As a rule a nominal torque is defined as torque at nominal speed. Pay attention that operation outside SOA allowed for short period of time. You must define cont/peak current of servo drive according to motor Spec also.