6 volt question

The sole function of a reverse current relay or cutout as its known to the industry is to sever the Battery from the system after the engine has been shut off. The charging of the Generator is controlled by the three postion switch with increases or decreses the ground to the Generators Field circuit. It is a multi-function switch and also controls the lighting on board the Tractor. As a short-cut or for testing purposes, you can run a jumper wire from the Generators field circuit to the engine block or good ground to full field the Gennie. This will let you know whether the Gennie is charging or not via the ammeter.  If you have the three postion switch in your ammeter box, make sure it is grounded correctly. This is a self grounding switch, so it needs to be grounded in order to get the correct charging rates. As far as replacing your cutout with a Voltage Regulator, you can do that. Wiring will be a fuzz different, the the VR will do the work automatically instead of the 3 position switch. Just remember to disgard the "F" field circuit to the 3 pos. switch before you install you VR.   HTH   If you need any electrical components, wiring harness, info, or help, just drop me a line, be glad to help you out.....

The cutout disconnects the generator when the engine is off. If it didn't, the generator will want to spin like a motor and drain the battery.

In a shunt wound machine like the generator, if you hold the field current constant, the generated voltage will be directly proportional to the shaft speed. So if it makes 6 volts at say 1000 RPM, it will make 12 volts at 2000 RPM. Where its run self excited and the field current varies with the output voltage it won't take as much speed increase to get to 12 volts, but I can't predict that any closer because it is affected a great deal by what field current saturates the magnetic circuit.

The current rating of the generator is not affected by its terminal voltage, that current rating is set by the heating of the current in the armature windings.

They did make 12 volt and 24 volt generators that looked exactly like 6 volt generators. Alternators for cars and small trucks came later than the switch to 12 volts (and for tractors too, JD used generators up to about 1970 on 3020 and 4020 up to 24 volts in the diesel models).

Some say its OK to use the same armature at 6 and 12 volts but say its a good idea to change the field coils because 12 volts on a marginal field coil made for 6 volts is going to cook it eventually or sooner.

Conversely a 12 volt generator regulated to 6 volts charges like an alternator at very low engine speeds. Using a diode (as Steve sells as an option) for the cutout increases the charging efficiency because the cutout take several amps of reverse current before it switches off and that often happens just above engine idle speeds when I"ve had a good ammeter to monitor the charging system (not shown by a voltmeter).

A regulator has two or three relay like devices inside. ONE is the cutout, one is the voltage regulator and the third may be a current regulator that backs off on the field current if the current gets up to the generator rating.

Gerald J.

Thanks Steve. Keep It Simple So us guys who don't have slide rule holsters on our belt can understand these shunt wound machines.

Thanks for the enlightenment Coke. I'm laughing so hard I can't hardly use the keyboard. Guess I spent too many years at a chemical plant.

yea Steve, I picked up on Gerald's little zing bout the voltmeter!!!  Sometimes its better to let sleeping dogs lie!!!!!!!  At least thats what Im gonna do!!!!  Heh!!