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single phase motors.

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Arbalist:
Many years ago someone gave me a motor of around 1/2 HP for a small Lathe I had and no matter which way I wired it, it would only run one way. I asked the guy who gave it to me about this and he said some motors can't be reversed. Is this correct? It wasn't a problem for me as I was able to physically mount the motor the other way round!

Manxmodder:
I had a similar situation a few months back,a mate gave me a brushless ac motor to put on a small bench drill.

It had the wrong rotational direction and to correct it I had to press the rotor of the shaft and press it back on the other way round. Just reversing the whole rotor assembly would have worked but the keyway in the shaft would have ended up on the wrong end of the motor......OZ.

hermetic:
Hi Arbalist, yes it is correct that some motors cannot be reversed, because the manufacturers "hide" the wires or connections you need to do the reversing. It also happens with motors like the old fashioned shunt universal (AC/DC) motors where you have to reverse the brush holder connections.........but the wires arent long enough!! If you are willing to tear the motor to bits and extend/alter wiring, you can usually do it, but it is more sensible to get another motor.
Phil

DavidA:
Hi,  doing a bit of dead thread resurrection.

I happened to be wondering why the motor (subject of above posts) gets so hot when running.

Could it be because the because the start winding and it's associated capacitor are always in circuit ? And thus are across the run winding.

I was thinking that the phase difference between the two windings may be causing the heating.

Perhaps a modification to cut the start winding out when the motor is running would be beneficial, what are your thoughts ?

vintageandclassicrepairs:
Hi David,
In my experience (35+yrs) I have never seen the run winding with a higher resistance than the start
so I think the capacitor is connected to the wrong winding ????
Have you measured the current when the motor is running and compared it to the data plate?
No load amps will be much lower than full load, but incorrectly connected amp readings will be higher
Of course cheap imported motors will not have top quality lamination's and these will run hotter
There maybe a temp rise figure on the data plate ?


John

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