Shunt Generator Field Coil Resistance

Thread Starter

Dave2000

Joined Oct 15, 2019
2
I rewound my own field coils in an automotive 12volt shut type generator. The original field coils in series were 3.2 ohms but my new ones I made in series measure 1.6 ohms. The length of wire (132'), size (20 awg) and number of turns are identical as the original but resistance is lower. I am wonder will this be okay as it is connected to an external voltage/current regulator that will perhaps limit the current to the field? Or should I install a resistor in series with the field coil to match the original specs of the field resistance? Or am I all wrong in my thinking?

Thanks,
Dave
 

TeeKay6

Joined Apr 20, 2019
382
I rewound my own field coils in an automotive 12volt shut type generator. The original field coils in series were 3.2 ohms but my new ones I made in series measure 1.6 ohms. The length of wire (132'), size (20 awg) and number of turns are identical as the original but resistance is lower. I am wonder will this be okay as it is connected to an external voltage/current regulator that will perhaps limit the current to the field? Or should I install a resistor in series with the field coil to match the original specs of the field resistance? Or am I all wrong in my thinking?

Thanks,
Dave
If the same length and same size wire produces 1/2 the resistance, then SOMETHING is wrong.
 

Dodgydave

Joined Jun 22, 2012
8,389
20Awg at 132 feet is 1.34 ohms,

your old wire is 24Awg at 132 feet is 3.4 ohms.

Dynamos work on Excited Field voltage, by putting the Field winding across the output of the generator, and then disconnecting them at the regulated voltage, if your windings are lower in resistance it will produce a bigger magnetic field.
 
Last edited:

Thread Starter

Dave2000

Joined Oct 15, 2019
2
As I was typing the clarification below I did some further testing and I believe one of the two coils has a short after being fitted in the generator housing. Thanks for the help guys, Problem solved!!

I should have stated the values a bit more clear. The wire length is 132' per coil not total. So I the new and old coils are as follows;

New coils: 264' of wire 20awg wire reading 1.6 ohms (measured diameter with micrometer 0.32")
Old coils: 264' of wire 20awg wire reading 3.2 ohms (measured diameter with micrometer 0.31")
 

MisterBill2

Joined Jan 23, 2018
3,874
As I was typing the clarification below I did some further testing and I believe one of the two coils has a short after being fitted in the generator housing. Thanks for the help guys, Problem solved!!

I should have stated the values a bit more clear. The wire length is 132' per coil not total. So I the new and old coils are as follows;

New coils: 264' of wire 20awg wire reading 1.6 ohms (measured diameter with micrometer 0.32")
Old coils: 264' of wire 20awg wire reading 3.2 ohms (measured diameter with micrometer 0.31")
A shorted circuit will certainly cause problems with motor coils. So now you just need to repair the problem. Good luck!
 
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