Testing 3 phase motors

I am testing a couple of 3 phase motors I have acquired. I have a single phase to 3 phase 3/4 hp rotary converter that generates the 3 phase field. I have checked a couple motors but when I tested 2 Baldor motors I tripped my fused switches. The first heated my switch red hot and the second turned slowly then killed my FRS 5 fuses in my converter set up. Both were 2-3 hp but I checked a different manufacturer 3 hp motor and it ran fine. So at this point I need to get more fuses. I had the motors wired for low voltage to match my 240 supply. I checked these wiring configurations thoroughly.

How do I test these 3 phase motors? I checked resistance between a 3 leads and measured a couple of ohms each. No spikes.

Also, I am looking to use these 3 phase motors for an idler in a separate rotary phase converter. I have read about getting a balanced voltage. Would this be just measuring the 3 voltages from the 3 different combinations of leads? What is a decent balanced voltage supply - say for mills or lathes?

Thanks Pal

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You seem to be doing the testing of the 2 or 3 HP 3 phase motors properly. If the motor is possibly faulty, maybe you can evaluate it by connecting a

12 VDC battery to any two of the leads to the 3 phase motor and test the resistance to 'twisting the rotor shaft'.

If you want any additional assistance with your testing you are welcome to E-mail me at home.


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Jerry Martes

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