Single phase motor reverse rotation

[westward10]

You shouldn't need to spin the wheel.
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what you need is a variac. you start it on a lower voltage then increase as it spins up.

This may prevent the start switch activating quick enough.

 

[waigy]

I'm only spinning the wheel to stop the sudden jolt from over tightening the buffing wheel.
The buffing wheel is on a threaded tapered rod and the wheel tightens onto the thread by itself.
This motor starts far too quickly which forces the buffing wheel very tightly onto the thread.
As I mentioned before, it also starts fast enough for the metal tapered spindle to come loose on the shaft.
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I got this motor for 20 quid so I don't fancy paying a fortune for a variac.
Is there a cheap way of gradually increasing the speed?

 

[telectrix]

You shouldn't need to spin the wheel.
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This may prevent the start switch activating quick enough.

years ago, when working i development of motors, we used this method to obtain the parameters for stalling, overvolts, and pull-out torque. was fun doing the "test to destruction" bits. forgot most of the tech. stuff now.

 

[Lucien Nunes]

Looks to me like two caps in parallel between two left terminals. Bottom left has line, 2 caps and run winding, top left has 2 caps and start winding. A picture of the rating plate would help clarify what kind of animal this is.

Yes, Variac start is good. 500W floodlight start is cheaper. Not keen to get involved with anything that might launch a polishing mop c/w taper spindle at its operator though!

 

[waigy]

The kw output part was badly scratched and I can't make out what it says but It has a 5 and maybe a 1 so I have assumed it is 1.5kw.
I emailed the company that makes them and they couldn't confirm the kw power as it's from the 70s.

I've spent a lot of time searching online and can't find an identical motor anywhere to double check the power output.
It's bloody powerful for polishing though, I can almost lift the motor off the ground pushing a part against the buffing wheel and it isn't even thinking about slowing the motor.
I reckon 1.5kw seems about right or 2hp.
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[Lucien Nunes]

Yes, the line current is correct for 2hp. If there's no centrifugal switch it's permanent split capacitor, hence the need for two large cap boxes (continuously rated run caps are bigger than start caps).

 

[waigy]

I'm pretty sure it doesn't have a centrifugal switch.
When I took the motor shaft out to change the bearings the casing inside was pretty much empty apart from the magnet/winding part.
And the shaft was just very basic like this with a bearing on each end.

 

[Lucien Nunes]

PSC it is then

 

[waigy]

Does PSC make it any easier or harder to make it gradually speed up or to have a speed controller?

 

[waigy]

This is one of the capacitors I think they are both the same.

 

[Dilwyn]

To confirm are you spinning it by hand to get reverse motion.

Hi I changed the polarity to a single phase motor by changing over. The 2 red live wires that had 2 capacitors works fine