>Many an alternator will definately self energize! If you look at the 'one
>wire' 6 volt and 12 volt alternators that are offered for sale, they have no
>external excitation.
>
One wire alternators are unheard of over here together with 6V versions. They
might though have external excitation as the one wire presumably goes to the
battery and the field could be permanently excited at a very low current
probably insufficient to be significant relative to the battery self-discharge
rate.
The standard UK mil 24V 90A alternator to cover all applications not only has a
remote regulator but the stator 3Ø AC output is brought out separately and the
whole machine is not frame grounded, the negative diode connection is a separate
terminal.
>My local starter/generator shop owner (old geezer) told me that most GM
>alternators from the later 70's-80's will run one wire. Before he sells one
>(like the one I bought) from him, he tests them to make sure that they will
>self energize. The only problem with these alternators is that you usually
>need a higher rpm to get them to flash over and start. This can be a problem
>with older mv's. My M6 Chev Bomb truck has one as do two of my CCKW's. On
>the Chevy with the dipper engine, you start the truck, let it warm up for a
>minute then put your hands over your ears and push down on the gas until the
>Ammeter shows a charge. What a noise that engine makes...
>
There is certainly a possibility that a tiny amount of residual magnetism might
remain in an alternator and high revs could have it begin to self-sustain,
however I've not found any of the common UK ones that will do this.
The dipper Chevy engine is not apparently renown for its robustness especially
being revved hard, as most alternators are dynamically balanced and good for at
least 10,000 RPM, most domestic ones here are specified to 12,000 RPM, it is
worthwhile to arrange for a substantial gear-up in the engine/alternator pulley
ratios. Most of the W.W.II engines do not exceed a nominal 3000 RPM or
thereabouts and may be governed, so 3:1 is not inappropriate.
Richard
(Southampton UK)
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