480 volt motor quandry 2

[NIDinc]

We are build our own custom 240 vac 3 phase inductive motor in our shop from scratch. This is a 2 hp small motor that is only about 3 1/2" diameter by 8" long. Last week we built a 480 volt version of the same exact motor, and it has drawn very amps.

We have checked and re-checked our windings and connections and are confident that it is correct for 480v. About the only thing I can think of is that we didn't put phase seperators in the windings.

Should be drawing about 1.5 amps and it was at about 8.
Any thoughts or input will be much appreciated.

 

[NIDinc]

Attached is a photo of the print for our stator lamination with most dimensions. All in inches. Again, designed as a 2 hp motor at 250Hz. We're attempting to apply it to a new application in which it will be running on a VFD at 20Hz - 120 Hz. The voltage at 120Hz will be about 115v. Amp load probably not more than about 4.5 amp.

 

[LionelHutz]

Hmm, when I read you had a VFD my first thought was that you forgot about the V/Hz ratio. What you actually did was build a motor with a 480V/250Hz = 1.92V/Hz ratio, correct?

Using the VFD to produce 480V @ 60Hz = 8V/Hz which is 4 times the ratio the motor was designed for and using the VFD to produce 480V @ 120Hz = 4V/Hz which is 2 times the ratio the motor is designed for. Both are caused by an incorrect VFD setup.

There is no reason you can't run the motor at 120Hz. The VFD can surely supply the correct 230V @ 120Hz.