VFD noise and motor frame material?
VFD noise and motor frame material?
(OP)
For a VFD-driven motor, does the material of the motor frame make much difference in the noise emitted from the VFD's carrier frequency? I know cast iron has higher damping than steel or aluminum, but I'm not sure how much this damping actually affects the acoustic noise in practice. If the effect is negligible, I'd prefer to get a lighter motor rather than a CI. (I know I can dial the VFD up above ~12 kHz, but some people can hear that, too.)
Thanks for any insights,
David
Thanks for any insights,
David





RE: VFD noise and motor frame material?
I guess it comes down to the amount of copper and iron within induction motors.
Don't forget, with some (most) VFD's that you will have to de-rate them if you wish to increase the CF, due to the increased heat of the VFD and therefore less efficient operation for the same output.
RE: VFD noise and motor frame material?
RE: VFD noise and motor frame material?
One could almost see how the cover vibrated. Hand in glove damped it and we later sprayed foam on the inside of it. That was all that was needed to quiet that one.
So, I think it is difficult so say in general if aluminum or cast-iron is louder. Parts that resonate can exist on both types. And it is the resonaces that create the highest sound levels.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD noise and motor frame material?
I agree many variables for motor noise in general and vfd introduces more
Cast iron has better material damping properties than the other materials steel and aluminum, which in general would lead us to suspect lower noise with "all other things being equal". Considering that all other things being equal requires a somewhat philosophical view since it is impossible experiment to change only the damping characteristics only ... when we change the material we also change stiffness and density which affects resonances. BUT, there are som many excitations and possible resonances that without more information one cannot say one material is more likely to be close to resonance than another. And at resonance is where the damping properties are most important.
See below including referenced posted by some guy named electricpete:
http://mai
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(2B)+(2B)' ?
RE: VFD noise and motor frame material?
Yes, I'm watching the derating curves for higher carrier freqs... fortunately the VFD I'm looking at (Hitachi WJ200-37) has no derate for my room temps.
For the motor, I think I've now narrowed it down to a Baldor Super-E (5 HP), which is offered with either a steel or cast iron frame. I'll try asking them if it makes much difference for noise.
Thanks again!