I have a 575V with only 460V input for testing purposes only

[Lovison]

We need to do a quick running test. However the motor is
a 575V. We only have 460V. We've been told by the
motor supplier we could do this but to limit the run time
to 15 minutes to prevent over-heating.

The FLA are 226 @ 1.0 SF and its a 449TC Frame NEMA motor.

Should I set the motor for 226 as the nameplate reads or
less? Amps should go up with lower voltage so I'm hoping
there is enough motor to at least make duty.

Testing today let me know if there is anything I should
look for or expect. Nameplate speed is 1184 RPM I would
also suspect a lower speed with less voltage am I correct? Wayne E. Lovison
service-parts@naglepumps.com

 

[redtrumpet]

Do you think it is prudent to run a motor at rated load for 15 minutes at only 80% of rated voltage? What do you think your customer would think if he found out about this?

Why not use a 600-480 V autotransformer and do the test properly, rather than "hope there is enough motor to at least make duty."

 

[buzzp]

The speed of the motor will not be lower, once up to full speed it will still remain the same as you mentioned. The OL device will still be set at SFA. Depending on how much overcurrent you have will determine how long you can run it. If you pull 600% of FLA, then you can only run for whatever time the TC(trip class) setting is; ie TC of 20 means it needs to trip in 20 seconds if pulling 600% of FLA. This is not very desirable to do what your doing. But if precautions are made, you should not damage the motor. Good luck.

 

[Lovison]

I appreciate your feedback. I don't like this any more than you do. But we can't waive the test and it may not have to run more than 5 minutes.

I agree with the autotransformer statement and I will look into that later but I'm cornered and a test must be made today - so bare with me. And by the way the Customer knows about our voltage situation and agrees as does the motor supplier to a short running test to confirm hydraulics.

We've talked about bringing in a 575V system but haven't done it just yet. (I know shame on me) but I do appreciate all of your concerns and want you to know this isn't a common practice.

Thanks Again




Wayne E. Lovison
service-parts@naglepumps.com

 

[busbar]

Wayne—

Is it about a 200-/250-hp motor? The 460V run should only be considered if the motor is not anywhere near fully loaded.

If there are no neutral-connected loads, the {cheapest,} hands-down universal solution is a pair of open-delta auto-connected 480:120V transformers; temporary or permanent. Someone else needs to confirm the calcs, but it looks like a pair of 50kVA units would work. [The shipping will probably be a major part of the invoice total here.] Other than that, with the possible exception of renting a big [diesel?] engine-generator set or carting the assembly to a place with a spare 250kVA @600V, I think you may be S.O.L. A lot of motor-repair shops have 480V-only service to test run 600V motors, but they can test with no load.