Really need inverter duty motors?
Really need inverter duty motors?
(OP)
I have an application where we need to put a few ac motors on a small machine. The motors are 3/4hp and will be speed controlled with a vfd. The size of the inverter duty motors is a big concern as the machine is pretty small. Is there a chance that inverter duty motors are really not needed? On these machines, the motors are speed scaled with an analog signal but the speed is constant per product - much like controlling the speed of a conveyor. Anyone have experience with this? The only literature I can find on the need for inverter duty motors is put out there by the manufacturers of these same motors...





RE: Really need inverter duty motors?
Standard duty motors may not be and therefor may fail
due to voltage spikes generated by the VFD.
RE: Really need inverter duty motors?
Suggest contacting several motor vendors: Marathon Electric, Leeson Electric, USEM, Baldor, etc... and discuss application with them. That way you will have their recommendation, and the confidence that the motor they recommend will serve your application well.
Other than that, and without a lot more specific detail, we'd all be just guessing.
jO
RE: Really need inverter duty motors?
My understanding of the subject:-
For EX Hazardous Area Applications the motors must be Inverter Rated, as well as EX certified of course.
For Non-Hazardous Area applications, motors simply require derating (as jO suggests, motor manufacturer will advise), more so with constant torque (e.g conveyor belt) than variable torque.
Alan
RE: Really need inverter duty motors?
RE: Really need inverter duty motors?
What voltage is the application?
RE: Really need inverter duty motors?
RE: Really need inverter duty motors?
If I understand correctly, stress voltage build-up may happen because of possible cable length. This seems not to be your application case.
Anyway, you are supposed to face additional PWM inverter operation caused motor loss that via potential overheating may lead to 20-25% motor power derating.
For some more info on machine PWM loss see PWM loss article overview at
http://www.drbrushless.com/cgi-bin/articles.phtml
RE: Really need inverter duty motors?
Of course you have to oversize the motor so you can trade torque for speed when you go over the base frequency(60hz).
Barry