> I have seen a simpler system: simply a (higher voltage) light bulb across
the
> same phase of the two generators.
>=20
> When the generators are at different frequencies, the light flickers.
> When the frequencies are closer, the flicker slows down.
> When both are at the same frequency but different phases the light stays
> steady.
> When at the same frequency and phase, the light stays off.
>=20

This mechanism is also used on the Boeing 727.  The flight engineer (the gu=
y
sitting sideways in the cockpit) would switch in three ac generators onto a
common bus.  There was one generator per engine connect via a variable spee=
d
drive unit.  The FE would adjust the speed of the drive until the flashing
yellow lights went out, and then close the circuit breaker on that generato=
r
to add it to the AC bus.

Dave Challis

--=20
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