motor whining 1

[bigheadted]

I have recently fitted a dc motor 16.7kw to a machine and noticed that the motor tends to whine quite loudly. i have been informed that this is common and will quieten down after a while is this true, what causes the whine is it harmonics if so why does it whine and why does it get quiter after a while?
thanx

 

[Skogsgurra]

Hello Ted,

I assume that this is a motor that is connected to a thyristor rectifier.

The whining is natural. It comes from the rectification of the three phases and the frequency is 300 Hz (if 50 Hz mains) or 360 Hz (if 60 Hz mains).

Getting quieter over time? No. I don't think it will. They probably mean that you will get used to it. One reason for excessive whining could be that the motor is mounted on a steel support and that you are getting a resonance at 300/360 Hz.

Anyhow, it is not bad for the motor. Unless you see fire under the brushes. You can reduce the noise by putting a DC (air-gap!) reactor in series with armature. Sometimes by finding a suitable wooden wedge and apply it somewhere to reduce resonance. Done that. You will need a sledge-hammer to make it sit securely. (It is not a recommendable solution, though).

Gunnar Englund

http://www.gke.org

 

[bigheadted]

yes youre right it is connected to a dc drive sorry i should have said. why would this motor whine and the one it replaces not?
thanks 4 your help

 

[Skogsgurra]

Identical motors? Same make? One cast iron, the other not?

Gunnar Englund

http://www.gke.org

 

[bigheadted]

both abb motors both same name plate etc

 

[Skogsgurra]

Hmm...

Someone else?

Gunnar Englund

http://www.gke.org