JMOR A and B circuit answer

Janicholson · Jul 10, 2012

In a "A" circuit system, the field is externally grounded by the VR or Charge control switch. It gets its power from attachment to the arm (hot) brush inside the gen, or from a third brush picking up electricity (a little remotely) from the commutator segments. Thus when the bat to gen (or arm) jumper is used the field gets current through their windings. This creates residual magnetism in the iron of the field poles.
In a "B" circuit system, the field is grounded inside the generator directly to the case. The field terminal is provided with voltage from the regulation system (not grounded at all). Thus polarizing a B circuit requires flashing the Bat to the F terminal. Momentarily energizing the Field coils to make residual magnetism of the correct magnetic polarity.

Polarizing improperly can and will ruin regulator control components, or not do anything. Jim

JMOR · Jul 10, 2012

Jim, I probably didn"t do a decent job of explaining what I was getting at in my question as to why the BATT to ARM jumper used in polarizing the "A"-ckt gen will not also work to polarize the "B"-ckt generator. In the violet colors, I show a path from battery neg, to VR"s BATT term, jumpered to VR"s ARM term, thru the VR field contacts,and out to gen field, thru field coils, and thru ground back to battery"s + terminal. This looks to me like it should provide field polarizing current. I could just never see the reason that a different polarizing method was always recommended for A & B???????? Seems to me that if this was always done, then people wouldn"t mess up and runi field contacts by jumpering BATT to Field on an A -ckt. They would ALWAYS be doing same procedure no matter "A" or"B"....BATT to ARM. Hope I"m clear as to what I was trying to get at. I guess it is just academic anyway, since the "different" methods are so ingrained.

http://i192.photobucket.com/albums/z232/JMOR_photo/Charging/polarizeB cktviaBatttoARM.jpg

Owen Aaland · Jul 10, 2012

The field coil pole shoes are what need to be magnetized for the generator to start to charge.

For an A type system, in a two brush generator, the A terminal is connected to both the insulated brush and one end of the field coil. The other end of the field coil is connected to the F terminal. In a three brush generator the field coil is connected to this extra brush instead of the A terminal and then the F terminal like a two brush unit.

When you apply battery voltage to the A terminal in an A circuit type generator to polarize it, the current flows from the A terminal through the field coil, back out through the F terminal and is then grounded inside the regulator by the normally closed field relay. In the case of a three brush generator the current must also pass through the windings of the armature to get to the third brush before entering the field coil. In both types there is also current passing though the armature to ground but that has no affect on polarizing the pole shoes.

In a B circuit type system you still need to polarize the pole shoes but the only connection between the A terminal and the field coil is that they share a common ground inside the generator. Energizing the A terminal will not cause any current flow through the field coils since it will merely end at the common ground connection. In order to have the necessary current flow though the field coil to magnetize the pole shoes there must be battery voltage applied the the F terminal. The F terminal relay in the regulator is in an open position so there will be no voltage applied to the field coil by applying voltage to the A terminal of the regulator.

JMOR · Jul 11, 2012

(quoted from post at 22:25:16 07/10/12) The field coil pole shoes are what need to be magnetized for the generator to start to charge.

For an A type system, in a two brush generator, the A terminal is connected to both the insulated brush and one end of the field coil. The other end of the field coil is connected to the F terminal. In a three brush generator the field coil is connected to this extra brush instead of the A terminal and then the F terminal like a two brush unit.

When you apply battery voltage to the A terminal in an A circuit type generator to polarize it, the current flows from the A terminal through the field coil, back out through the F terminal and is then grounded inside the regulator by the normally closed field relay. In the case of a three brush generator the current must also pass through the windings of the armature to get to the third brush before entering the field coil. In both types there is also current passing though the armature to ground but that has no affect on polarizing the pole shoes.

In a B circuit type system you still need to polarize the pole shoes but the only connection between the A terminal and the field coil is that they share a common ground inside the generator. Energizing the A terminal will not cause any current flow through the field coils since it will merely end at the common ground connection. In order to have the necessary current flow though the field coil to magnetize the pole shoes there must be battery voltage applied the the F terminal. The F terminal relay in the regulator is in an open position so there will be no voltage applied to the field coil by applying voltage to the A terminal of the regulator.

This sentence is correct ONLY WHEN generator CHARGING current has pushed the battery voltage so high as to no longer call for charging (typically ~14,4 volts); "The F terminal relay in the regulator is in an open position so there will be no voltage applied to the field coil by applying voltage to the A terminal of the regulator". Just as in the "A" VR, the field contacts in the "B" VR are closed in a static non-running situation, therefore appling 12v ( or 6v in 5v system) to the ARM terminal WILL in fact push current through the field coils. Note: the same is true of field contacts being closed at rest in both the "A" and "B" ckt VRs AND both will be carrying field polarizing current when voltage applied to the ARM terminal..........power path in "B" ckt & ground path in the "A" ckt.

JMOR A and B circuit answer

Janicholson

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JMOR

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Owen Aaland

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JMOR

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