Large inductor downstream of DC motor controller.

[whiskytango]

I have a 30 year old polishing machine that is used in the semiconductor industry. The electrical path is:
120VAC ==>> Motor Controler ==>> Inductor ==>> DC Motor.

The DC motor is rated at 90VDC @ 12A.
The motor controller failed so I replaced it with a Minarik motor controller that was rated for such a motor. The data sheet for the new Minarik motor contoller says nothing about inserting an inductor between the controller and the motor.
I removed the inductor and the polishing machine works fine as far as I can determine.

Does anyone know the purpose of this large inductor?
The printing on the inductor is:
T29942
25mH @ 4A D.C.
Made for SIMPLATROLL by AUTOMAT. LTD STOCK No K4-116667.2

It weighs about a US pound or two.

 

[Skogsgurra]

Inductors are used to reduce armature current ripple. They were common when thyristor bridges were "half-controlled" and produced a lot of ripple.

Modern thyristor controllers are fully controlled and usually do not need the external inductor.

If your motor is happy, then you are safe. But, if there is severe arcing under the brushes, you may try to insert it again and see if that helps.

Gunnar Englund

http://www.gke.org

 

[whiskytango]

Thanks Gunnar,

It sounds like I can re-install the inductor with no adverse effect.

-Ira

 

[powerjunx]

whisk,

inductor in series is used as a filter. It filters the output of the old controller to reduce ripples. Evidently 30 years old would mean controllers were not completely tuned to its purpose. But nowadays, inductors are included on the controller itself. So external inductor is not fitted unless your motor is roughly running.

It's good to be adventurous!