Speed control with droop compensation

[weerachay]

Hi all,

In my AC-Drive Inverter, there are a few modes of operation such as, speed control, torque control, speed control with droop compensation. I quite understand about speed control as master drive and torque control as slave drive, but what is speed control with droop compensation means and why do we have to use this mode of operation. I have seen them using speed control as master drive and speed control with droop compensation in slave drive.

Thank you in advance.

 

[RadarRay]

Droop compensation, in affect, makes the speed regulation softer. It usually consists of a feedback from the torque fb (or amature current feedback on DC drives), feed back to subtract from the reference going into the speed regulator.

This is just the opposite of what was called "IR compensation" which would be used when a DC drive is run in Armature Voltage Feedback mode. In this case the DC drive would add a signal to the speed reference to compensate for the IR drop in the motor as the load goes up.

From the drive application stand point, it is usually used to prevent two drives which are running in speed mode from fighting each other. This would happen if the motors or loads on the motors are coupled together. Typically, if two motors are coupled together, it is impossible to run them both is speed control because it is impossible to prevent the Integrator in the speed regulator from eventually winding up. Typically they would wind up in opposite directions. One motoring, the other regeneration.

They actually do not have to be coupled together. If for example they were conveying a web between driven rolls, and the web was inelastic and would not slip, they would be affectively coupled together.

You did not describe the exact application but I assume it is similar to the one I described.

 

[jbartos]

Suggestion: The speed droop develops when the load causes a speed decrease and the speed regulator will not bring it to the reference speed, e.g. 1000RPM. The speed will stay at about some small fraction below 1000RPM. This is in some application intolerable; therefore, the speed control with the droop compensation is applied. It means that the speed droop will be compensated and the 1000RPM speed will be restored under the heavy load that caused the speed droop. There are various droops, e.g. voltage droop, frequency droop, speed droop, etc.

 

[jbartos]

Suggestion: Visit

http://www.cptthailand.com/Main/manual/Eurotherm/DC Drive/508.pdf

etc. for more info in terms of IR compensation by a potentiometer