Unused alternator winding

[EEBlackSheep]

I have a motorcycle that is being converted to a race bike.  It has two independent windings in the alternator, one for the electronic ignition, another high current winding for lights etc.  It is *not* a typical three phase motorcycle alternator 0- just two independent windings.   Since it is being converted to a race bike, there is no need for the high current winding (there will be no lights, battery or electric start, just the electronic ignition).

What do I do with the unused winding?  One schematic shows that it should be shorted out; but a number of people on the motorcycle forums says the circuit should be left open.  I would like to understand why - one way or the other.

thanks for the help.

[c4757p]

The winding is a power supply. If you short it out, it will attempt to supply power to the wire with which you have done that. Bad. Best case, it makes the alternator act as a brake. Medium, the wire melts. Worst, the wire in the alternator melts.

If you leave it open, it simply won't supply power. Everyone's happy.

The outlets in your house are supplied by a winding on a transformer, too. You don't short those out when not in use, do you? 

[CodeDog]

is it a permanent magnet alternator?

if so, their windings can be shorted/earthed with no ill effect ... otherwise the shunt regulators
on most motorcycles wouldn't work ...

leaving them open cct is feasible but for safety take care to insulate the floating connector as reasonably large voltages are likely to be generated at high RPMs

it would be good if someone knowledgeable on the subject of permanent magnet alternators could explain
the counter-intuitive result that the output can safely be shorted

[G7PSK]

If its a flywheel type alternator just remove the whole coil.

[Richard Head]

If you short it it will act as an electromagnetic brake and sap power from the engine. The power loss will appear as heat in the flywheel and the windings.

Dick

[tautech]

Often there are 3 windings, power, ignition exciter and ignition trigger windings. They are commonly on a single stator. You could possibly un-wind the one you don't need, but I would leave it open circuit, unless the little extra weight worries you. If you leave it there, just be sure any remaining leads are well insulated.

[Dave Turner]

All else being equal leave it alone. Removing will  probably cause unwanted effects.

[SoundTech-LG]

Short it out, and never win any races
Leave it open, and maybe you will...

[IanB]

is it a permanent magnet alternator?

if so, their windings can be shorted/earthed with no ill effect ... otherwise the shunt regulators
on most motorcycles wouldn't work ...

leaving them open cct is feasible but for safety take care to insulate the floating connector as reasonably large voltages are likely to be generated at high RPMs

it would be good if someone knowledgeable on the subject of permanent magnet alternators could explain
the counter-intuitive result that the output can safely be shorted

I don't think the output can safely be shorted. If you short the output then current will flow through the short, the wiring and alternator will get hot, and the short circuit will act as a magnetic brake on the engine.

The output must be left open, and the output wires must be carefully tied off and insulated so they don't accidentally short against anything else.