Resistance of electrical motor windings?

It's been a very long time since I study days but I'm pretty sure when you measure the resistance across the windings of a motor it should be a low Ohm value not more than double digits?

Got a motor here with dual windings and the resistance is in the 150k-200k Ohm which does not sound right?

Can someone please confirm or deny my speculations above.

Edit: It's a small 200-250V AC 50Hz single phase jobbie.

Maybe its pico ohms? As in 200k x10^-9 ohms?

The windings should have a very low resistance. It's actually quite difficult to test for shorted windings in motors/transformers with a multimeter as the resistances are usually very low. I'm not sure though how you could be getting a high resistance value. If a winding shorts out due to an insulation fault the resistance should decrease further. Alternatively a short circuit could cause a winding to go open circuit if there is a break in one of the wires. Are you possibly accidentally measuring your skin resistance when taking the readings? Have you tested/replaced the capacitor/brushes etc.? It is possible to get some AC motors rewound depending on the size. I had a lawnmower motor rewound for ~R500.

Sysem said:

Maybe its pico ohms? As in 200k x10^-9 ohms?

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Nah, multimeter is on the 200k Ohm scale, if I drop it below that scale it registers nothing.

Yotch said:

The windings should have a very low resistance. It's actually quite difficult to test for shorted windings in motors/transformers with a multimeter as the resistances are usually very low. I'm not sure though how you could be getting a high resistance value. If a winding shorts out due to an insulation fault the resistance should decrease further. Alternatively a short circuit could cause a winding to go open circuit if there is a break in one of the wires. Are you possibly accidentally measuring your skin resistance when taking the readings? Have you tested/replaced the capacitor/brushes etc.? It is possible to get some AC motors rewound depending on the size. I had a lawnmower motor rewound for ~R500.

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I actually stripped the motor so I only have the casing containing the windings, the capacitor wires are disconnected. It's a motor from 1978.

I will try measuring again tomorrow without any skin contact.

a winding reading in excess of 100k ohm is shot...

motor winding ohmic values range from 10 ohms to 400 odd ohms.

Koosi said:

a winding reading in excess of 100k ohm is shot...

motor winding ohmic values range from 10 ohms to 400 odd ohms.

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That's what I was thinking.

Uhhh.... are you measuring it with a magnet close by? I'm not certain, but that might be stuffing with the results...

All I know from motors and logic, is that you want lots of wire coils, and low resistance so that there's no power consumed by the wire, so that you get as much of the electric field fighting with the magnetic field...

Hmmm, 100kohm seems WAAAY to high.

Possible issues: Wire is broken, and you measuring the resistance of the wire and a tiny "gap" between the broken wire.
Are you using the write settings on your multi meter? Use a resistor you have lying around to see if it's actually measure the right resistance and not something else.

Remove all dirt and grime from the terminals or whatever you measuring the resistance with... remember also, that the wire has an insulation coating over it (enamel, so annoyingly, it looks like pure copper)... So if you measuring straight off the wire, maybe get a knife to remove that coating.

If all else fails, those motors make for fantastic paper weights.

As an aside, if your windings are actually using wire that has 200kOhm resistance, you'll be pumping the massive amount of 1.15mA rms... or 0.3 watts. So I can't imagine it being amazing in the first place.

scotty777 said:

Uhhh.... are you measuring it with a magnet close by? I'm not certain, but that might be stuffing with the results...

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No. I actually split the motor casing so I ended up with the casing part that contains only the stator (windings), no rotor/amature or any other schit.

ponder said:

No. I actually split the motor casing so I ended up with the casing part that contains only the stator (windings), no rotor/amature or any other schit.

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Just make sure that you aren't trying to measure results with exposed wire then, you might be experiencing the resistance of the enamel... I know that was a major problem when I built an electric motor