Alternator Measurement

Jim-Jim · Post by **Jim-Jim** » Sat Mar 15, 2003 5:06 pm

I know this may sound weird but, trust me, I have a valid reason for asking (future plans).
Has anybody ever measured the CURRENT (Amperage) in the alternator brush circuit? This would be for the rotor circuit which controls the output of the alternator. I know it is probably never done for troubleshooting (it should be) but I hope someone, somewhere, sometime just happened to make this measurement (and kept note of it).
Thanks.
Jim-Jim

Don · Post by **Don** » Wed Apr 02, 2003 9:16 pm

If it works anything like a normal alternator on a car, the rotor current isn't "fixed" and the amount of it isn't significant, as it changes according to the load on the electrical system.

The voltage regulator changes the voltage applied to the rotor circuit to control the current coming out of the alternator, so what's happening with the rotor circuit is dependant on several factors, and is frequently changing - More voltage (and thus more rotor current) when more load is applied, or when the battery is semi-discharged.

Don

Jim-Jim · Post by **Jim-Jim** » Wed Apr 02, 2003 10:54 pm

Don,
I know how the rotor circuit works

- what I asked if anybody had happened to measure the current.

I know it is not fixed and I know it controls how much voltage comes out of the stator and I know it varies according to the demand load of the output circuit and I know the rectifier/regulator controls the rotor current, etc - what I asked was if anybody had happened to measure it.

Jim-Jim

Don · Post by **Don** » Thu Apr 03, 2003 9:19 pm

Jim,

Not a "measurement" I know, but the rotor is 4 to 5 ohms in resistance, (got that from some hand written notes in my factory service manual) so if you "full field" it (apply 12 volts to the rotor) the resulting current should be between 2 1/2 and 3 amps - This do you any good?

Don