Alternator Regulator

[silvercbx]

I don't know if this should be here or in the Electrical main section but here goes. On a motorcycle website, we are having a vigorous debate on the Battery and Alternator/Rectifier/Regulator problems. To be specific, we have an Alternator that has a 3-phase stationary Stator and a wire wound rotating Rotor. The 3-phase Stator windings go directly into a 3-phase Rectifier and directly out to the Battery. No problem there. The Rotor is fed, on one side directly to Battery (through the IGN switch) and the other side is grounded by the R/R through a transistor that turns on/off. It is the turning on/off of the Rotor that controls the output from the Stator. The main bike wiring diagram shows the Xtr and the feed to the Rotor but show nothing about HOW the Xtr is controlled.
I'm trying to learn how the Xtr is controlled inside the Regulator. I'm assuming there is a Zener diode somewhere in there but how does the whole thing work? Can it be adjusted or is the Zener (if there) fixed and unchangeable?
If I could be pointed to an internal diagram of a Regulator, I could probably figure out what's going on in there. Some have posted that an R/R has a separate 'sense' wire that goes somewhere (but they cannot say any more).
Currently, we're all arguing about how the charge voltage is set and what limits can be applied to the current AGM batteries being used. Some say 13.6-.8, some say 14.3-.6 - one battery site says the AGM should 'never' be above 14.7-.9 or it will vent out.
I would appreciate any comments or guidance or directions.
Thanks.

 

[MikeHalloran]

It probably depends strongly on which motorcycle, since different engineers take different risks with a company's reputation.
You didn't say which motorcycle.
You also can't assume that they have three phase stators, or even wound rotors. There have been some bizarre setups in motorcycles.



It might be illuminative to find a shop manual for a car made in the sixties, equipped with an alternator and a mechanical regulator, and read up on how that regulator worked.

Within the regulator, there were typically three different coils that served three different purposes.
Modern cars' magical solid state regulators do not include an equivalent of the coil that limited how much current would be pumped into a near dead battery, which is why nowadays you often get to replace the alternator, the regulator, and the battery in rapid sequence when any one of them dies. I guess that's a discussion for another day.

Someone please illuminate what the other two coils did, eh?





Mike Halloran
Pembroke Pines, FL, USA

 

[silvercbx]

First off, most of the newer bikes DO have three phase Stators and, while some use Permanent Magnet Rotors, the ones I'm trying to deal with have BRUSHES which means a wound rotor. While it might be illuminative to read about the old mechanical regulators, I don't know that the electronic regulator has any equivalency. I'm trying to learn how the electronic regulator works (as I said).
But thanks for the input.

 

[GregLocock]

You could have a look in the Bosch electrical handbook (red cover)

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[waross]

Generators had three coils.
1. Reverse current coil.
2. Voltage limit coil.
3. Current limit coil.
Alternators did not need the reverse current coil, the diodes prevent reverse current.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[silvercbx]

Since I'm new here, and that list goes on forever, would you, please, point out my specific transgression on my post? I'm really sorry that I did something in error here.
Thanks

 

[GregLocock]

That's my sig (wow someone reads them), it is general advice not aimed at you.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[silvercbx]

We're getting kinda far astray here.
What I wanted to know is if anyone knew how a Regulator for a 3-phase Alternator with a wound rotor worked internally. The one I'm interested in works by turning the voltage/current to the Rotor on/off to control the Stator voltage. I want to know how it does that.

 

[GregLocock]

So did you lokk in the Bosch electrical handbook (red cover)?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[waross]

There are three basic control modes:
Slow on-off, the current is passed to the rotor. The stator voltage builds up. When the DC output voltage reaches the set point (13.8V?). the current to the rotor is interrupted. When the voltage drops a small amount the current is again allowed to flow in the rotor.
Modulated, The rotor current is modulated to provide a rotor field strength that holds the DC output voltage at the set point (13.8V?)
Pulse width modulated, The rotor supply voltage is switched rapidly between zero and 100% with a train of pulses. The ratio of the on times to the off times determines the average current and as a result the output voltage.
Put a scope on the output of the regulator.
On off will show a train of pulses between zero and 100% voltage. The frequency will probably be below 100Hz.
Modulated will show a steady output somewhere between zero and 100% voltage.
Pulse Width Modulated will show a train of pulses between zero and 100% voltage. The frequency will probably be above 1000 Hz.
100% of the regulator voltage to the rotor may not be 100% of the battery voltage.
The average voltage applied to the rotor will determine the current through the rotor circuit. The current through the rotor circuit and the speed will determine the open circuit output voltage.

Bill
--------------------
"Why not the best?"
Jimmy Carter