Alternator question - is this AC? Stator pic included

[baycloud]

Hey there all, I have a non-regulated GM style alternator (with no regulator), and a Balmar ARS5 regulator. I want to get a tachometer output. The Balmar can accept a stator input from the alternator. The alternator manufacturer told me this wire was voltage sense or stator which DC, which was confusing to me. I thought stator would mean AC. I wonder if they confused the regulated vs non regulated model.

My 2 questions are:

• is the pin highlighted below (the "R" pin) AC? It looks like it must be since it seems to be wired directly to a single stator coil
• What voltage should I expect when testing it? I know motorcycle stator voltage was ~30v if I recall

 

[JoeWhite]

I would think it would be pulsating DC rather than AC. Meaning the voltage does not go below zero volts, but remains above zero volts and fluctuates up then to zero. I am not sure what the peak voltage is, that would require an oscilloscope. It will indicate RPM.

 

[Maine Sail]

The green arrow is pointing to the stator tap. Who converted that alt to external regulation?

 

[baycloud]

The green arrow is pointing to the stator tap. Who converted that alt to external regulation?

I bought it that way since I want to use a balmar mc618 regulator

 

[Maine Sail]

A better question is who did you purchase it from?

 

[baycloud]

This stator should give

A better question is who did you purchase it from?

Here is the model. I am testing it out to use with a very small generator.
7102k Alternator

 

[mikeracca]

So this depends on how you look at an alternator. The name alone says it creates alternating current, which is does initially, but there is a diode pack in there that makes the current DC. Then there is a regulator that will attempt to keep a constant usable voltage. Alternators are more efficient and can also keep a steady current flow at a much wider RPM range than a DC generator can.

What you got there looks to me like an alternator. Just remember to put the brushes back into the holder and pin them I’m place before putting the armature back in. There should be a hole on the back plate designed to hold the brushes with a pin (a paperclip works great here).

 

[mikeracca]

The 7102 series alternators were an oddball in the GM lineup. They were used in 71/72 and were a stop gap between the older style externally regulated and the newer 7127 internally regulated family. I don’t know if they have a tach usable output on them, internally they were still pretty much the old school alternator. Also these only put out 35 to 40 amps on average, but some aftermarket replacements could get to 45a. The 7127 series can make up to 60 amps, and has much simpler wiring requirements, while having the exact same case dimensions as the 7102 does.

 

[Maine Sail]

This stator should give

Here is the model. I am testing it out to use with a very small generator.
7102k Alternator

The reason I ask is because that dummy regulator block is our design and our manufacturer promised us it was proprietary/only for us.. I would urge a strong caution on running that alt anywhere North of 60A or heat may kill it. We built a similar alternator only we used a much more robustrectifier& better quality internal components. We would not build one any larger than 100A as that case does tot have the cooling ability to go anywhere North of 100A..

 

[baycloud]

The reason I ask is because that dummy regulator block is our design and our manufacturer promised us it was proprietary/only for us.. I would urge a strong caution on running that alt anywhere North of 60A or heat may kill it. We built a similar alternator only we used a much more robustrectifier& better quality internal components. We would not build one any larger than 100A as that case does tot have the cooling ability to go anywhere North of 100A..

Interesting. Is there a better rectifier that would fit in there? I can solder new connections if needed

 

[baycloud]

So this depends on how you look at an alternator. The name alone says it creates alternating current, which is does initially, but there is a diode pack in there that makes the current DC. Then there is a regulator that will attempt to keep a constant usable voltage. Alternators are more efficient and can also keep a steady current flow at a much wider RPM range than a DC generator can.

What you got there looks to me like an alternator. Just remember to put the brushes back into the holder and pin them I’m place before putting the armature back in. There should be a hole on the back plate designed to hold the brushes with a pin (a paperclip works great here).

After staring at the brushes and pondering for a while I did end up figuring that out. After a while