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Fixing a small motor

Chris Pearson

I want to fix an ancient 1/8 hp motor (Carter Electrical Co Ltd). As far as I can tell, the centrifugal switch has worn out, so that will be fun making a new one.

My question is what resistance seems reasonable for the coils. IR is good (well into the tens of megaohms) but they are a little dark and I would like to be confident that there has been no internal shorting.

The main coil is about 18 ohms and the starting coil 33 ohms. My maths tells me that the running current should be around 0.4 A. I cannot remember a lot about motors, but I realise that the impedance of the coils will be higher at 50 Hz than the (DC) resistance and that back EMF reduces the current. I hope therefore that the resistance values are about right.

Grateful for any reassurance!

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    Looking further, I note that the modern carter company     only makes AC DC brushed and  traditional DC motors. - I'm assuming you have a capacitor-less induction design (where the starter coil phase shift is done by magnetic shunt or shorted turn - rather like the old fan heater motors and record deck motors with one winding and a shorting link to distort the magnetic flux.) ? If not some of what i said is not relevant.

    Mike.

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    Looking further, I note that the modern carter company     only makes AC DC brushed and  traditional DC motors. - I'm assuming you have a capacitor-less induction design (where the starter coil phase shift is done by magnetic shunt or shorted turn - rather like the old fan heater motors and record deck motors with one winding and a shorting link to distort the magnetic flux.) ? If not some of what i said is not relevant.

    Mike.

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