Single phase motor reverse rotation

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waigy

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Brook Crompton Parkinson single phase PD90S (from the 70s) 240v 11A 2850rpm 50hz

I'm using it for polishing metal with a tapered spindle adapter and buffing wheels.

I've got 2 questions.

1. (This photo was taken with all the wiring in its original position.)

I've managed to reverse the motor rotation by swapping the two black wires that are behind the copper connector, but after a few quick trials it is constantly blowing fuses.

Can you confirm that I have changed the correct wires to reverse the rotation?

2. The capacitor starts the motor with a massive jolt which forces the buffing wheel so far onto the tapered spindle that I need large pliers to loosen the buffing wheel.

If I fitted a smaller capacitor would it start more gently or is it possible to remove the capacitor and start the motor by hand by rotating the buffing wheel?

The white arrows point to the three wires that go inside to the motor.

P1010335.jpg.d9d14e544c04631041db74e360158026.jpg


 
UPDATE. I just sorted the problem of blowing fuses and the motor is rotating in the direction I want.

I fitted new bearings to the motor a couple of days ago and noticed straight away that the motor was more stiff to turn and wouldn't turn freely if twisted by hand.

I thought that was just the bearings being a tight fit, but I slackened the 3 long bolts that hold the whole casing together by just a touch and it loosened the shaft a lot and it now can spin freely by giving it a quick twist.

It now spins for a long time after the motor is switched off which it didn't do before.

So I've tightened the 3 bolts just enough to keep the motor spinning freely.

But I still have the problem of the capacitor starting the motor with too much force.

I have a metal tapered spindle slid onto the splined end of the shaft which is a fairly tight fit.

That is then held in position by a 6mm screw to stop it rotating on the shaft.

The capacitor starts the motor so violently that the 6mm screw can't hold the tapered spindle on.

I have managed a work around just now of spinning the buffing wheel by hand as fast as I can, then switching the motor on while the wheel is already spinning.
 

 
I can't find out anything about this motor.

I can't make out the kw power output on the label so emailed the company and they can't tell me because it's so old.

I also can't find the same motor anywhere on the internet to find out more.

I'm pretty sure it is 1.5kw.

_8j6-jpg.56036
_8ll6-jpg.56039


l_86-jpg.56037
_86-jpg.56038


 
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I can't access those photos for some reason.

However, can you read the value of the start capacitor?

If so try a smaller one, perhaps 50%, (less micro-farad, same voltage or higher). They are quite inexpensive and you won't do any harm as long as you don't leave it powered up whilst stalled, (i.e. if it doesn't start).  

Your application is free of starting load so it should start easily.

 
How do I find out which capacitor is the starting one?

On another forum someone reckoned it is a permanent split capacitor so does that mean it won't have a start capacitor?

Do these images work?

$_8j6.JPG$_8ll6.JPG$_86.JPG$l_86.JPG

 
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The 4 arrows point to wires that go into the motor.

P1010335wee.jpg

 
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Usually you reverse either the start winding or the run winding but not both .     Not sure about that motor though .  

Could you not just turn the motor around  180 deg.  ?   :C

 
It looks to me that the two capacitors are connected in parallel.  It also looks like they are in circuit all the time which fits with the other opinion you have been given.

A start capacitor would be wired via a centrifugal switch to take it out of circuit as the motor speeds up. Was there one when you stripped it to do the bearings?

 
I have the motor working fine in reverse rotation by swapping the two wires under the copper bar.

It doesn't have a centrifugal switch as when I took it apart to fit the bearings it was pretty much empty inside apart from the magnet/windings.

 
I have the motor working fine in reverse rotation by swapping the two wires under the copper bar.

It doesn't have a centrifugal switch as when I took it apart to fit the bearings it was pretty much empty inside apart from the magnet/windings.
In that case they are "run" capacitors, not just for starting. They effectively create a second phase and contribute to the power. 

I don't think there is much you can do about the start acceleration. Someone else may know a way.  ??

 
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