DC servo inductor

[headflow]

On my 1984 Faxac mill with Heidenhain controller and Infranor DC servo amplifiers theres a big inductors in series with the brushed DC motors.

They make a terrible squiling noise when I run the machine, I have tried to bypass them but then the motors run warmer and the sound generates from the motors instead (altough alot lower)

How can I make the machine silent?
Why is the inductor needed?
What value should new inductors have?

The drives are X: 15A\165V Y: 15A\165V Z: 30A\165V

Greatfull for help
Larsa

[Al_The_Man]

The inductors are not the cause just that they are taking some of the switching current.
These are used when motors are used that are lower than the rated load impedance of the drive.
You probabally have older, lower frequency switching drives and they are velocity drives as opposed to torque mode drives.
These often were set up with the gain setting at maximum before motor oscillation sets in, this was mainly due to velocity drives being soft around the zero point so the drives were switched 50% on 50% off at rest, alternatively in both polarities, this causes the 'singing' at rest as well as when moving, although it usually decreases when moving.
Al.