Keep the sets clean at all times.
Check the condition of the oil in all the bearings at least once a week and add
oil when needed. At the same time the machine is oiled, inspect the commutator.
If the commutator shows signs of burning or pitting, it should be cleaned off with
00 sand paper.
Several types of AC motors are used with these sets, depending upon the type
of power supplied in the theatre (single-phase, two-phase, or three-phase at 110, 220
or 440 volts). The care and operation of all of these types will be the same with the
exception of the single-phase motor. This motor is identical in principle with the
single-phase repulsion-induction projector drive motor previously discussed. In addition to checking the oil in this motor, the commutator should also be checked, and
the same treatment given it as prescribed for the generator commutator.
34. DC to AC Motor-Generator Sets. -In theatres where direct current only is
available, it becomes necessary to convert the direct current to alternating current
for use in the power amplifiers of PG-3, PG-4, PG-6, PG-7, PG-8 and PG-10 equipments. To do this, some sort of motor-generator set or its equivalent must be used.
One of the motor-generator sets used for this purpose is illustrated in Figure 26.
This motor-generator set is rated at 1/2 k-va. The drive motor is located at the left
and the generator to the right of the generator control panel. The electrical operation of the motor is similar to that of the DC projector drive motor previously
described, except that no speed regulating device is used.
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