Figure 7-19.Combination starter with a disconnect switch.
Figure 7-20.Combination starter with a thermal-magnetic
START-STOP STATION WITH A
Sometimes it is advisable to have a pilot light on
the push-button station to indicate whether the motor is
running. The lamp usually is mounted on the station
and is connected across the holding coil. Such a con-
nection is shown in figures 7-24 and 7-25. Figure 7-26
shows a control circuit with the pilot light on when the
motor is stopped. Normally closed contacts are needed
on this starter. When the motor is running, these con-
tacts are open. Contacts are closed when the motor is
stopped, and the pilot light goes on.
Modern methods of design and construction have
made the electric motor one of the least complicated
and most dependable forms of machinery in existence
and thereby have made the matter of its maintenance
one of comparative simplicity. This statement,
however, should not be taken to mean that proper
maintenance is not important; on the contrary, it must
be given careful consideration if the best performance
and longest life are to be expected from the motor. The
two major features, from the standpoint of their effect
upon the general performance of the motor, are those
of proper lubrication and the care given to insulation.
Lubrication and insulation protect the most vital, and
probably the most vulnerable, parts of the machine.
The designs of bearings and bearing housings of
motors have been remarkably improved. However,
this advance in design can cause problems. The bear-
ings of modem motors, whether sleeve, ball, or roller,
require infrequent attention. In the case of older
designs with housings less tight than on modem
machines, oiling and greasing are done frequently. The
perpetuation of this habit causes the oiling and
greasing of new motors to be overdone. The result is
that oil or grease is copiously and frequently applied to
the out-side, as well as the inside, of bearing housings.
Some excess lubricant is carried into the machine and
lodges on the windings where it catches dirt and there-
by hastens the ultimate failure of the insulation.