alternator question....

[RECHRGD]

When you ground one of the field wires on a dual field alternator to make it function as a single field unit, does the amp rating stay the same?  Thanks, Bob

[b5blue]

Amp output is a function of RPM's so yes and no. Yes you will excite output but amount increases with RPM.  (If I read your question correctly.)

[RECHRGD]

Amp output is a function of RPM's so yes and no. Yes you will excite output but amount increases with RPM.  (If I read your question correctly.)

Question is.......If the output is 65 amps at 2300 rpm when operating as a dual field unit, is it still 65 amps at 2300 rpm when wired as a single field unit?

[b5blue]

Boy ya got me! An alt. output is A.C. current rectified to D.C. by diodes. If you eliminate 1 of 2 fields, I would "assume" you would 1/2 the amps..... 

[RECHRGD]

What I've gathered from "Googling" the subject is;  There really is no difference between a "dual" field and single field alternator other than how the ground is wired.  I installed my new 90amp "dual" field yesterday wired in the single field configuration (attached second field terminal to a ground screw provided on the alternator case).  It obviously is putting out more amps than the stock unit.  The lights don't pulsate at idle anymore, the electric fan runs faster than before and the battery recovers from the starting load much quicker.  All is well....Bob

[A383Wing]

Output is the same...no matter how it is wired...it's the regulator that controls output

[RECHRGD]

Output is the same...no matter how it is wired...it's the regulator that controls output

[mhinders]

When you ground one of the field wires on a dual field alternator to make it function as a single field unit, does the amp rating stay the same?  Thanks, Bob

I can only answer in general terms since I don't know how the 2 internal field windings are internally connected.
The field winding is supplying the magnetic field, stronger magnetic field gives a higher output from the alternator. If one of 2 field windings is not contributing to the magnetic field, the output will be lower, unless the remaining single field can take significantly increased field current to compensate for the lower magnetic field. The voltage regulator is regulating the current in the field windings, which in turns control the output from the alternator.
Martin

[Nacho-RT74]

"dual field" alt is the same than a "single field" alt, the difference is what field is the regulated one.

on single fields, the ground ( negative ) brush is chassis grounded, and positive is isolated from chassis for double reason... any chassis contact will short ( obvious reason ), PLUS this is the regulated field from regulator. As far just one of the field is decreased ir increased by the regulator the complete magentic field willl change proportionally.

THEN "dual fields" got BOTH brushes isolated. Positive for the obvious reason with chassis. THEN THE NEGATIVE was isolated because on electronic regulators THIS IS NOW the regulated field/source, not anymore the positive what it's sourced now directly from ign switch, so negative can't be in contact with chassis because will be sending full output ( both sources being constant ). Thats the reason why both brushes are isolated now

when you ground one of the brushes on "dual field" alts you still will need to get one source regulated and this will be the positive source coming from MECHANICAL REGULATORS. So thats why you are converting a "dual field" on a "single field".

so as you can see the regulator system is what actually makes the work to select what alternator will use or how will you set up this alt.

ACTUALLY all alternators are dual field. thats an incorrect term really because all alternators need to be dual field to create magentic fields inside. The reason why call it like that is because you are wiring one or two fields at brushes.

So on earliers, the green wire arriving to alt, is a regulated positive and on laters the green wire is STILL the regulated source but now NEGATIVE. Blue is positive and constant from ign switch

[mhinders]

Ok, interesting, there's nothing like "dual field", only "single field terminal" and "dual field terminals" alternators.

I thought that there had been some development with the "dual field alternator", but it turns out the only difference is that the old field ground point has become isolated in the later models.

Now it seems (on the web) that 1 of the 2 field ends is connected to +12V, while the other end is connected to the electronic regulator. The voltage regulator is sensing the system voltage, and adjusting the current through the one and single field winding to control the output from the alternator.

The only reason I see for this slight modification of the alternator is that it's somewhat easier (and cheaper) using electronic circuits to control a voltage near ground (0V) than up at 12V, i.e. easier and cheaper to control the current in the field winding with the "dual field terminals".

The "dual field terminals" type can be used as the old one by grounding one field terminal.

If I have understood all this correctly, it means that 2 different types of electronic voltage regulators are available? The old style with grounded field terminal will need a regulator outputting 12V to the field terminal, while the newer using both field terminals will need a regulator that is pulling to ground.

[b5blue]

Now look into "remote sensing" detecting current demand at it's highest point in the harness.....that will get ya scratching your head. 

[Nacho-RT74]

Ok, interesting, there's nothing like "dual field", only "single field terminal" and "dual field terminals" alternators.

I thought that there had been some development with the "dual field alternator", but it turns out the only difference is that the old field ground point has become isolated in the later models.

Now it seems (on the web) that 1 of the 2 field ends is connected to +12V, while the other end is connected to the electronic regulator. The voltage regulator is sensing the system voltage, and adjusting the current through the one and single field winding to control the output from the alternator.

The only reason I see for this slight modification of the alternator is that it's somewhat easier (and cheaper) using electronic circuits to control a voltage near ground (0V) than up at 12V, i.e. easier and cheaper to control the current in the field winding with the "dual field terminals".

The "dual field terminals" type can be used as the old one by grounding one field terminal.

If I have understood all this correctly, it means that 2 different types of electronic voltage regulators are available? The old style with grounded field terminal will need a regulator outputting 12V to the field terminal, while the newer using both field terminals will need a regulator that is pulling to ground.

EXACTLY... I couldn't tell it better!

however, we can't talk about 0 Volts or 12 Volts like talking about AC. We talk about - source and + source on 12 DC volts because is DC coming from electrochemical reaction at batt, or rectified from AC to DC inside the alternator.