AC Permanent Magnet Motor Noise 1

[Franko]

(fixed title)
With a permanent magnet AC motor, for reducing noise, should the stator slots be completely filled? If so, is it best to use magnetic, non-magnetic, or semi-magnetic material? Also, are there service shops that can treat stators that have unfilled slots?

 

[UKpete]

Franko, it is possible that there will be a reduction in audible noise if you fill the slots, assuming the conductors are relatively loose. Another benefit of filling the slots is to improve the thermal conductivity between the copper winding and the laminated core, in order to reduce the winding temperature. Of course, the end-windings should also be well secured with lacing chord and consolidated with an impregnating resin. This will also improve the life of the winding.

The material should be NON-MAGNETIC and non-conductive otherwise you will deterimentally affect the performance of the motor. A well designed motor will already have a good copper fill in the slot, this after all will result in lower copper loss. But you can improve the fill of the slot using an impregnation resin such as epoxy or polyester of suitable temperature rating. Techniques such as vacuum-pressure impregnation (VPI) or simple dipping may not be very effective if the copper fill isn't high, as the resin tends to run out during curing. So you might try a "trickle" resin, these are thixotropic and should stay in place. There are plenty of resin suppliers, e.g. in the US:

http://www.pdgeorge.com/

In answer to your final question, any rewind shop should be able to help.