Hammond Model A, Руководство пользователя, Страница: 84 / 298

CONSOLE POWER WIRING
(Main and Chorus Generators)
Starting and Synchronous Motors
A shaded pole induction motor is used for starting the generator and is located at
the right end of the generator as viewed from the back. The rotor of this motor will
slide endwise when current is supplied and engage a pinion on its shaft with a gear
on the generator driving shaft, bringing the tone generator up to slightly greater
than synchronous speed.
When the organ is started, the starting switch is turned on and held for about 8
seconds while the starting motor brings the system up to speed. The run switch is
then turned on. This switch simultaneously connects the synchronous motor and
introduces a resistor in series with the starting motor (figure 1), thus reducing
its driving power. With a braking action of the synchronous motor and a loss of
power of the starting motor, the system slows to synchronous speed and the
synchronous motor begins to carry the load. A period of about 8 seconds should be
allowed for this to take place, after which the starting switch may be released. The
starting switch springs back to the off position, and turns off the starting motor,
which is disengaged from the rotating shaft by a spring.
It should be noted that the synchronous motor can supply power only at synchronous
speed. Therefore, if for any reason the system fails to reach synchronous speed it
will not continue to run after the starting switch is released. Failure to start
properly is usually due to increased oil viscosity and may be overcome by an
increase in starting time.
As the schematic diagram (figure 1) indicates, the run switch in its off position
shorts out the wirewound resistor attached to the line panel. If the run switch is
defective in its off position, the generator will not start because this resistor
will be permanently in series with the starting motor. Before assuming that there is
anything amiss with the motors, short out this resistor and start the generator in
the normal manner. If the generator operates satisfactorily, replace the run
switch.
The run switch on all consoles is a two-circuit switch. but types of switches
having two different terminal arrangements have been used, as shown in figure 2.
When replacing a switch, observe the wiring of the old switch and check the
connections of the new switch with an ohmmeter. Note that black and blue are
connected in the on position. and yellow and brown are connected in the off
position, no matter which type of switch is used.
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