3 phase motor

[Newpark7]

Hi

This is probably a basic question but I have just wired in a large radial arm drill for a customer all working except the slurry lubrication pump. It has a 3 phase motor but only has 3 leads coming from the windings can someone explain how to go about testing this please.

I have done an IR test between each lead and the case all read >2000 the readings between each lead are >2000 >2000 & 600meg

There is no continuity between any of the windings using the ohms function of a multimeter.

Can I assume open circuit windings? What sort of readings would a good motor have.

There is 430 volts between each line and no current draw from any line.

Thanks

 

[johnboy6083]

i can only assume that the motor has already been connected as star or delta, and the three connection points for your three phases have been brought out for you to connect to. Not unlike a submersible/borehole pump. What readings are you getting between the windings? The reason you may not be getting a reading on your multimeter is because it may be out of your meters range.

 

[Knobhead]

If there are only three terminals it’s most likely to be star connected. Given that you’re getting different readings to earth for each winding points to failed windings. CR readings for such a small motor would normally be around 20/30Ώ, the main thing is that they should be in balance.

 

[Newpark7]

Ok thank you - so to test the windings do I measure resistance between each of three wires in turn or each wire and earth. I understand if there was 6 wires you could measure each pair of each of the three windings.

 

[Steve Riley]

First check that the motor rotates, these little suds pumps get clogged with swarf and old coolant. They will, however, sit there quite happily stalled and not usually burn out.

Radial arm drills aren't used much for production these days, if its just a few holes a squeezy bottle of coolant would be a lot less messy!

regards, Steve