More dual field alt questions- what was its advantage?

[Ghoste]

Forgive my ignorance, but what was the advantage Mopar gained by switching to the dual field alternator?

[John_Kunkel]

I can only speculate but I think they did it to eliminate ground problems at the alternator; by controlling the ground at the regulator instead of the alternator they eliminated grounding inconsistency between the various contact surfaces....again, just thinking out loud. 

[Charger RT]

Maybe it was the start of ground control. They still use the same system right up to at least a few years ago cars. Most circuits on mopar fuel injected cars control circuits with grounds.
Tim

[Ghoste]

So no performance advantage from a purely charging point of view?

[Nacho-RT74]

not really sure, but I think the dual field alt is actually a consecuence of the newer electronic reg design. I meant, the dual field alt is a need what born from the newer regulator design, and not backwards.

performance or not ?... well, electronic regulators are known like more efficient than the mechs, so if we can say thats a better response part of the charging system, actually becomes on a "performance" upgrade... don't you think ?

[Ghoste]

I meant more from the terms JUST of the alternators performance.

[Ghoste]

Didn't they start installing dual field alternators BEFORE they started using electronic regulators?

[John_Kunkel]

The factory electronic regulator appeared at the same time the dual-field alternator did but, since almost all aftermarket regulators for the single-field are now electronic, the point is moot....they could have kept the single-field and changed to electronic regulators.

In '70 the powers-to-be at Mopar knew the electronic ignition was right around the corner and the electronic regulator is favored with EI.

[Ghoste]

Okay thanks John.  I had thought the dual field started showing up in 69 and the regulator was 71.

[Nacho-RT74]

nop as I told you, the dual field alt was a need for the elec reg... now whats the reason why now is regulated by ground? I think John got a good argument

In 71 ( actually 72 ) what it was new is the SQUARE BACK, alt with all are dual field by default. Round backs can be found in both setups

[resq302]

hmmm.  Here I thought the square back started in 70. 69 and older was the round backs.   

[Nacho-RT74]

nop... lates 69s C bodies got the first electronic regulators setups, then 70 was standard up to 71s all these years still getting roundbacks BUT dual field... some of them, specially earliers, are casted ready to get any of the setups without mods, dual or single, just getting the propper brush and isolator.

[Ghoste]

So how is it that the electronic regulator operates that the dual field alt is required?

[Nacho-RT74]

you mean on round backs ?

[Ghoste]

Yes.  Or at least I think so. 
Basically I'd like to understand how it all works.  I understand how an alternator works, I understand how regulators work.  I understand the points one versus the transistorized one.  In short I have a simple grasp of the concepts behind it all.  What I don't understand is how a dual field interacts with the electronic regulator in such a way that its use in necessitated.  Why is the round back one different from the quareback one in this case?
I don't need the in depth engineers perspective but I guess I'd like the next step beyond where my limited knowledge is currently.

[Nacho-RT74]

Ok, the dual field and single field makes reference just on how many prongs or brushes are wired on back of the alt. Actually ALL ALTS gets dual field because you need negative field and positive field to create the full magnetic field into rotor, and when this spins, the stator captures that. Diodes banks gets converted/rectified the ALTERNATING CURRENT ( reason why it calls alternator ) into DIRECT CURRENT. The positive side of the sinusoidal alternate signal is captured and send to the stud then to the batt by the positive diodes, and the same with negative side of the sinusoidal signal, but to the chassis, then to the batt.

How the regulator works ?... no matter if electronic or mechanical, they regulate JUST ONE FIELD. With just get the control over one of the fields into the alt, the full magnetic field inside the alt is completelly under control

Now, why do we have "dual" field and "single" fields ? which really is single prong or dual prong, or wired sources, or isolated brushes

earliers mechanical setups, send a positive regulated source through the green wire ( what it takes from blue ign source ). Alternator gets constant negative with the brush mounted on directly on case, without isolation, then this regulated positive source from regulator arrives to an ISOLATED brush ( needs to be isolated due is a positive mounted on a chassis and is also regulated ), controlling the full magnetic field, then the alt output. Need to note than THIS mechanical regulators also needs to be good grounded, to be able to work the system inside, but won't be the signal to be sent to the alt.

Laters electronic setups regulates NEGATIVE side of the fields ( also being a green wire ). Being this the new process, BOTH fields on alt needs to be isolated. Why? because if you don't isolate the brush feeded from the constant positive signal ( blue wire from ign switch ) will short with alt chassis, AND if you don't isolate the negative signal brush, won't be anymore a REGULATED source, so you are not regulating anything and will get max output from alt ALWAYS. You'll be FULL FEEDING BOTH FIELDS ALL THE TIME.

These electronic regulators get the negative source from chassis and the positive source from ign switch ( blue wire ), being the positive source just to make it work, and this time the negative source from chassis, usually called ground is the source to be sent to the alt after be regulated

I hope sounds clear. You know my mother language is not english and sometimes it can be hard to me explian this kind of stuff.

the reason WHY the electronic regulators changed the system to regulate the negative field ? personally don't know, but John could get the point on what he explained

[Ghoste]

No, very helpful Nacho.  One more question then.  With the aftermarket electronic regulator that has been modified to hook into the older wiring set up for a single field alternator, how do they operate to make this possible?

[Nacho-RT74]

simply using different electronics inside than the stock electronic regulators. Remember we have PNP and NPN transistors ( positives and negatives ), better electronics now than then etc...

I bet the "stock" elec regulators available now are not anymore the same than first units used either.

Now you can see why no matter if roundback or squareback you can work any of the alts on any of the systems, as far are correctly sourced &/or modified/matched for that.

You can ground one of the brushes on a dual field alt to convert it into a "single" field alt, OR, modify the case of the single field ( if not disposed from fact like someones did ) drilling a big hole on it to fit the isolated brush assembly into the housing and convert it into a "dual" field alt.

remember last roundbacks WERE ALREADY BUILT FOR DUAL FIELD SYSTEM, between 70 AND 71, and some roundbacks sold as service parts, were disposed on rear housing to be used on any of the setup just using the right brush setup, no need to modify, just service the right brush setup

The round and squareback change is not more than a diff diodes disposition, then the housing disposed for those new diodes disposition. Squarebacks are easier to service. Not anymore pressed in parts ( diodes ) or welded ( stator and diodes terminals ) like roundbacks were. Everything on squarebacks is bolted on: Nothing to do with more or less output.

EXCEPT ON MIDS/LATERS squarebacks alts, which got a wider stator, able to get more magnetic field

[Ghoste]

Thanks buddy. 

[Nacho-RT74]

I have adding and editing my replies where I found something to add or make corrections. Just in case, take care of the last updates

[mhinders]

I think the explanation regarding the single connection version versus the dual connection version is very simple.

With a mechanical charge regulator you automatically  deal with 12V, the electromechanical relay is chopping the 12V to keep it stable, you simply feed the chopped 12V to the positive side of the field and ground the other side.

With the need to have more precise regulation you get into electronics. With electronics it is cheaper and easier to control the ground connection (to control it at 12V makes the electronics more complicated and more expensive). You feed the full 12V to one end of the field winding , and you pull out the previously grounded end of the field winding and let a bit of electronics control the grounding. By keeping it shorted to ground you have full output from the alternator, and you simply decrease the output by having short periods when no current if flowing thru the field winding (i.e. not grounded).

The advantage with the dual version is that you get far better charge control with an electronic regulator.

[Ghoste]

Unless you use one of the retrofit electronic ones that can currently be used with the single alt?

[Nacho-RT74]

not sure how much true is that. Ground is not more than NEGATIVE pole of DC... which is EXACTLY the same than what we call 12 volts positive, is simply POSITIVE from a DC source.

the only difference between + and - on our cars is the + is wired everywhere and for the - we use the chassis like a BIG BUSS BAR, saving on wiring

we just call it ground because we associate the same kind of installation on our tipical home and electrical ALTERNATE CURRENT devices using the chassis to ground the devices and systems, but actually on our cars the "ground" is really take the - pole of batt from the chassis buss, not really a ground.

so THERE IS NOT A DIFFERENCE or a truth on if - or + are one more effective than the other to be used, than just than the design used on how are wired on our cars.

Fiberglass cars are exactly the same, just using double of the wires required on a tipical sheetmetal assembly, because you won't get a GIANT BUSS BAR on chassis.

thats all.

[Nacho-RT74]

Unless you use one of the retrofit electronic ones that can currently be used with the single alt?

some ppl have tried those, without a big success. BUT dunno why. Not saying they don't work. Maybe is just about quality of manufacturer, but not really about if is better regulate + or regulate - using one or another electronic regulator

[Ghoste]

So you don't generally approve of using a single field alternator with one of the retrofit electronic regulators?