3 phase motor help

BobReeves · Jul 20, 2004

My neighbor has a large metal lathe that he is trying to get running and has solicited my help because I once told him how to properly wire an AC outlet.. /forums/images/graemlins/crazy.gif I have never messed with 3 phase motors so here I am asking for more help..

He bought a phase converter and has it wired to the lathe. The problem is it will run in one direction only. If you try to reverse it, it just sits there and hums. The wiring diagram on the motor is no help and he doesn't have any diagrams of the reversing switch on the lathe. I believe If I could see a diagram of a 3 phase motor and a reversing switch I might be able to trouble shoot the darn thing.. Anyone know of a web site that might have a diagram that will tell me what wires get switched to where when a 3 phase motor is reversed. Google was a nightmare of 3 phase theory but didn't find what I was really looking for.

Thanks

rockyridgefarm · Jul 20, 2004

Switch 2 of the three motor leads...

BobReeves · Jul 20, 2004

</font><font color="blue" class="small">( Switch 2 of the three motor leads... )</font>

Tried that before posting, the motor ran backwards with the switch forward but did the hum bit when the switch was reversed. In other words.. It just reversed the problem..

Thanks for trying to help...
Bob

dummy · Jul 20, 2004

this article might help, 3 phase On a true 3 phase setup, switching any one leg should cause reverse rotation. Did you swap legs on the motor or on the phase converter?

BobReeves · Jul 20, 2004

Ya, that will be a big help, will print it and attack with my meter tomorrow.... Switched wires on the motor and it did reverse. I think the problem is in the converter wiring or something is wrong with the reverse switch. Now that I have an idea of how this thing works I am pretty sure I can fix it.

Thanks
Bob

dummy · Jul 21, 2004

Hopefully, it will help. Did you swap the legs going into the converter?

BobReeves · Jul 21, 2004

Found the problem was in the switch, once I had the diagram it was really pretty simple to troubleshoot.

The switch is a big rotary job that is forward-off-reverse The one leg that doesn't get reversed was only making contact in the forward position. In the reverse position the motor only had power to two of the legs.

Now the problem is locating a replacement switch. This is a Chinese lathe of unknown brand so we may have to use a little Oklahoma engineering to get something working. At least now we know what the problem is.

Appreciate all the help and suggestions, am reasonably sure we can either come up with a like switch or do a little modifying to make what we can find work..

Bob