Re: Re: Re: Re: oops put power to field of gen

Posted by Gary_N_WV on September 27, 2003 at 10:57:04 from (69.43.20.75):

In Reply to: Re: Re: Re: oops put power to field of gen posted by Doug in OR on September 27, 2003 at 08:45:08:

A field coil has "resistance"..... any time you pass current thru a resistance, there is a difference of potential across it, sometimes refered to as an "IR drop".
And yes....if you ground the field terminal, the generator will charge.....but were is the other end of the wire that a field coil is made up of?....It is connected to the Battery (in one fashion or another).
Usually, when the relay that controls the field current is open , there is a small resistance added in series with the circuit. If you look on the bottom of a voltage regulator you will see a wirewound resistor which is wound around a piece of ceramic.....this is the resistance.
When 2 resistances are put in the field circuit (the little wirewound one and the "field coil" itself, the battery voltage is devided between them,....lets assume for clarity that both the wire wound and the field coil is of equal resistance...when both are in the circuit, there would be 1/2 the battery voltage across each one....so, your field coil would have 1/2 the voltage across it ...but, when your relay grounds the field, which shorts across the resistor mounted on the voltage regulator, then you have the full battery voltage across the field windings.

Anyway, ....this is all "moot".......We have gotten off the track of what "happy" seemed to be concerned about, and that was ...if the generator was ruined by applying battery voltage across the field winding....and I doubt it !

Gary

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