Synchronous motors questions

[GoatZero]

 i have been reading about synchronous motors, and i actually got one from a microwave , i was playing around with it and suddenly when i was spinning the propeller i got shocked, by touching the terminals

i pulled out a multimetter to meassure voltage in CD and CA and both are getting generated, (way more CA than CD)

so now i wonder

Why is this happening?

Is it generating AC or DC ?

Whats the max voltage i can get from spining this thing ?

I have to go out i will plug it to an oscilloscope later tonight however i wanted to ask so maybe someone gere can give me any leads of why is this happening

[peter.mitchell]

it's a 120v motor rated for 6 rpm.

it will generate AC, at a pretty high voltage, put your multimeter on it in ac, stick it in a vice/vise and SLOWLY spin the shaft with your hand, and then with a drill to see what kind of voltage you get, you might be surprised.

[sleemanj]

maybe someone gere can give me any leads of why is this happening

Ask yourself the question"what is the difference between a motor and a generator".

[amyk]

it will generate AC, at a pretty high voltage, put your multimeter on it in ac, stick it in a vice/vise and SLOWLY spin the shaft with your hand, and then with a drill to see what kind of voltage you get, you might be surprised.

I wouldn't advise the latter - this looks like a geared motor with a very high reduction ratio (designed for 6RPM out) and pushing it much beyond that has a high chance of breaking something.

[Zero999]

That's exactly why he said slowly.

It's not only the gears which could be a problem, if you spin it too quickly, the output voltage could be too high for the insulation, causing it to arc over.

[SeanB]

As it is a synchronous motor it has a permanent magnet on a shaft. Turn the magnet and you make a changing magnetic field in a coil of wire, which generates a voltage. Slightly different construction is used to make an alternator like in your portable genset, but the principles are the same.