Dual Voltage Motors Needed?

[Beggar]

Strictly to test our control logic and our panel builds, we'd like to briefly run at no load several Baldor motors (7.5-20 hp) which are spec'd to be 380V/50 Hz. Our power supply is 480/60.

Given that there's no load and that we'd only be doing it for 60-90 seconds, is there any possibility of damaging the motors?

The vendor who quoted the system came back after we cut a PO for a duplicate system of one previously built and now says that they didn't quote dual-voltage motors on the new system and that if we want them then they have to increase the price. Of course, I don't want to pay any more than I need to.

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[motorsdirect]

I would say there is a fair possibility that damage would be caused!!! Just the one i.e. 380v - 480v....or 50 - 60 hz would be bad enough on its own...but I would imagine this would be like a 40% overvoltage!....I would say dont do it!!!
Jeff

http://www.motors-direct.co.uk

 

[aolalde]

Those Baldor motors can be tested at 480 Volts 60 Hz without any problem.

An induction motor will have an equivalent magnetic load if the ratio Volt/Hertz is keep constant.

This motors are rated 380 Volts, 50 HZ so RatioV/HZ=380/50=7.6

The equivalent voltage at 60 HZ is; 7.6x60 = 456 Volts.

If your test is at 480 Volts the percent of overvoltage applied is; 480/456x100 =105.3%

Almost any standard for motor manufacture allows 5% overvoltage, NEMA allows up to 10% overvoltage.

 

[motorsdirect]

Hmmmmmm.
Not so sure that I agree with that....would be very interested to know the results of your testing!!

Jeff

http://www.motors-direct.co.uk

 

[jraef]

I agree with aolalde in light of your intended use. It should make no difference in the short term. Realize that it will run 20% faster, but uncoupled that probably makes no difference to you for logic testing. I used to even do it with an old 240V motor that I had connected to a 480V supply. It ran hot if I left it on for more than 3-4 minutes, but usually I was just testing an OL trip or current sensing relay so it was always a very short run like yours. That motor lasted 5 years of repeated duty like that, then I sold it to someone else in working condition and 7 years later it is still running (albeit at 240V supply). I doubt that I caused significant damage in the short test runs I did.

"Venditori de oleum-vipera non vigere excordis populi"

 

[DickDV]

You'll be ok as long as long they are unloaded. 380/50 motors are used all the time on imported machines in the US at 460/60 and, as long as they are not overloaded, generally last a long time.

 

[mc5w]

MOST modern motors are rated to operate at 380 volts 50 Hertz and 480 volts 60 Hertz. There is even a Spanish manufacturer of thread rolling machines that puts dual diameter sheaves on the motors and dual diameter grooves on the flywheel. The only thing that needs to be done when changing frequencies is loosen the belts and move them to the appropriate diameter grooves, then retighten the belts.

This outfit is B$ting you about a higher price.

Mike Cole, mc5w@eathlink.net