Stick in the Fan

[SnowRidge]

Once an alternator with an internal regulator starts producing an output, it should become self exciting. It sounds like Charlie has an alternator with an internal regulator, since he said that he was advised to hook it up as a single wire unit.

If it maintains roughly 14 1/2 volts once started, it sounds like it is regulating properly.

 

[J_J]

Once an alternator with an internal regulator starts producing an output, it should become self exciting. It sounds like Charlie has an alternator with an internal regulator, since he said that he was advised to hook it up as a single wire unit.

If it maintains roughly 14 1/2 volts once started, it sounds like it is regulating properly.

Maybe, but even if it's an internal regulator, the voltage regulator part of the alternator has to send the correct voltage to the field, no voltage to the field, no amps or regulation. A permanent magnet alternator is self exciting. If you can spin it, it will charge, but you still have to regulate the voltage.

And, yes, if Charlie applies 12 v to the field, it will charge at max amps. That is a quick way for any alternator to give a quick fast charge.

 

[SnowRidge]

Maybe, but even if it's an internal regulator, the voltage regulator part of the alternator has to send the correct voltage to the field, no voltage to the field, no amps or regulation. A permanent magnet alternator is self exciting. If you can spin it, it will charge, but you still have to regulate the voltage.

And, yes, if Charlie applies 12 v to the field, it will charge at max amps. That is a quick way for any alternator to give a quick fast charge.

JJ, I'm not sure what point you are making. He doesn't have a permanent magnet alternator. If he did, he wouldn't need to excite it externally to get it started.

Permanent magnet alternators are shunt regulated. They put out their full capacity at all times. The excess is shunted to ground through components mounted on a heat sink.

Conventional alternators with internal regulators don't need external wiring to connect the regulator to the field. It is done internally.

 

[J_J]

JJ, I'm not sure what point you are making. He doesn't have a permanent magnet alternator. If he did, he wouldn't need to excite it externally to get it started.

Permanent magnet alternators are shunt regulated. They put out their full capacity at all times. The excess is shunted to ground through components mounted on a heat sink.

Conventional alternators with internal regulators don't need external wiring to connect the regulator to the field. It is done internally.

I agree that some regulators are located at a distance from the alternator, and some regulators are located on the back of the alternator, and the others are located inside the case. They all do the same thing.

It would be good to see a wiring diagram.


All that you said above is true. We are saying the same thing. Charlie has not described his complete set up. The point is, it seems like he is bypassing the regulator, and when you do that, you force the alternator to put out max amps. You should really go through a regulator for automatic operation.

Some tractors do have permanent magnet alternators, and maybe that is a good thing.

 

[J_J]

Nice alternator lesson.

Alternator Fundamentals - Alternator and Voltage Regulator Operation

 

[SnowRidge]

I don't believe he is bypassing the regulator. He is just supplying excitation voltage momentarily. The same line was connected permanently to 12 volts as wired by PT, if I understand his posts correctly. There should be no problem.

 

[Charlie_Iliff]

How about wiring the alternator excitation connection to the "START" position on the ignition switch? That way, excitation voltage is applied only while you are cranking the engine with the starter motor.

Tim: I tried that and it simply didn't work. I don't know why. The voltage drops, of course, with the starter, but I still expected the alternator to kick in. It didn't.

 

[Charlie_Iliff]

Charlie, Does your system have an internal regulator, or external regulator.

The IGN switch voltage goes to the regulator via the IGN terminal on the regulator, which then excites the field windings by sending the correct amount of voltage to excite the field. If the regulator doesn't have any feed back from the alternator, then I don't think it will supply any voltage to the field windings. On your setup, you need some way to vary the field voltage so as not to overcharge the battery. It seems like I had seen an old timer touch the battery voltage to the field terminal to test the alternators he was rebuilding. By doing that, he forced the alternator to put out max amps. This guy was good, he could take a bad alternator and rebuild it in about 20 min. He had a test stand with an AC motor that turned a belt to the alternator. It's hard to find those guys anymore. Most people just take it in to Autozone or Napa, and get a replacement.

It's internally regulated. Once started, it kicks to 14+ and then gradually backs down to about 13, so the regulator is working fine. It worked also when wired by PT with continuous 12V to that post, which my guru identified as the idiot light post, which excites the field through a light, thus at less than 12V, but then puts 12V from the alternator to that post while running, so the idiot light has 12V on each side and doesn't light.