Author Topic: Capacitor start motor, changing direction  (Read 544 times)

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Offline JesterTopic starter

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Capacitor start motor, changing direction
« on: August 29, 2021, 11:38:53 pm »
I picked up a band saw that was missing the original 1/2HP ac motor. I thought I could use a spare 1/2 HP motor I had laying around from an old drill press that I converted to 3-phase with VFD. The surplus drill press motor fits perfectly, however the direction of rotation is reverse to what is needed for the band saw.
I opened it up hoping to reverse the start winding and this is what I found. The diagram is my best guess as to how the wiring actually is based on ohm meter readings.

The blue wire appears to be common to both windings, so I don't think I can reverse it without pulling the field windngs out and bringing out a second wire, any experts out there to verify my best guess.

I can't actually see the connections from the colored wires to the magnet wire.
« Last Edit: August 30, 2021, 12:30:12 am by Jester »
 

Offline CaptDon

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Re: Capacitor start motor, changing direction
« Reply #1 on: August 30, 2021, 01:56:57 am »
Looks like you may have to do some surgery on it to find the other end of the start winding.
I worked at a machine shop many years back and we removed the start capacitor completely
from the motor on a drill press. You had to turn on power and manually give the chuck a spin
in the desired direction to start the motor. This was super handy for using 'reversed drills' that
are used to drill out broken screws/studs/etc. Of course you needed common sense when
'spinning it up' to not get clothing wrapped into the chuck!! We never had any mishaps, but we
had intelligent people who knew and accepted the dangers. (Kind of like when we were allowed
to jump off moving trains doing classification in the freight yards!!!! Can't do that anymore!!!!
Had to dumb it down to the lowest common denominator!!!) I used to put rolling stock from behind
the locomotive into a siding ahead of the locomotive facing the direction of travel!!! That is when
I had a brakeman and conductor as my crew. (Back when railroading was fun and unions
didn't suck and you had work/family balance!!!)

 
Collector and repairer of vintage and not so vintage electronic gadgets and test equipment. What's the difference between a pizza and a musician? A pizza can feed a family of four!! Classically trained guitarist. Sound engineer.
 
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Offline JesterTopic starter

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Re: Capacitor start motor, changing direction
« Reply #2 on: September 02, 2021, 03:31:50 am »
I was able to access the field windings enough to separate the common connection (run & start) and bring out a separate wire for the start winding. It was a bit easier than anticipated.

It's now working CCW! :-+
 


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