certain arc chutes are securely fastened. Be sure
example of troubleshooting a motor-controller
there is enough clearance to prevent interference
electrical system is given in a sequence of steps
when the switch or contact is opened or closed.
that may be used in locating a fault (fig. 10-10).
Replace shunts and flexible connectors, which
We will analyze the power circuit and then the
control circuit.
are flexed by the motion of moving parts, when
worn, broken, or frayed.
Regularly test the CBs by testing them on how
they are intended to function. For manually
POWER CIRCUIT ANALYSIS
operated CBs, simply open and close the breaker
to check the mechanical operation. To check the
When no visual signs of circuit failure can be
mechanical operation and the control wiring, test
located and an electrical failure is indicated in the
electrically operated CBs by the operating switch
power circuit, first check the line voltage and fuses
or control. Exercise care not to disrupt any
(or CB), as shown in figure 10-10. Place the
electric power supply that is vital to the operation
voltmeter probes on the hot side of the line fuses
of the ship. Also, be careful not to endanger
as shown at position A. A line voltage reading
personnel by inadvertently starting motors and
tells you that your voltmeter
is operational. It
energizing equipment under repair.
tells you that you have voltage to the source side
Before returning a CB to service, inspect all
o f the line fuses. Y o u may also check
mechanical and electrical connections. These
between the other lines. To check the fuse in line 1
include mounting bolts and screws, drawout
(L1), place the voltmeter across the line fuse as
disconnect devices, and control wiring. Tighten
where necessary. Give the breaker a final clean-
ing with a cloth or compressed air. Operate
manually to be certain all moving parts function
freely. Check the insulation resistance with a
Megger before reinstalling the CB in the SWBD.
CONTROLLER
TROUBLESHOOTING
Although the Navy maintains a policy of
preventive maintenance, sometimes trouble is
unavoidable. In general, when a controller fails
to operate or signs of trouble (heat, smoke, or
smell of burning) occur, you can find the cause
of the trouble by a simple examination using the
sense of feel, sight, or smell. However, at other
times, finding the trouble involves more detailed
actions.
Troubles tend to gather around mechanical
moving parts. Problems also occur where
electrical systems are interrupted by the making
and breaking of contacts. Center your attention
in these areas.
When a motor-controller system has failed and
pressing the START button will not start the
system, press the overload relay reset push
buttons. Then attempt to start the motor; if the
motor operation is restored, no further checks are
required. However, if you hear the controller
contacts close but the motor fails to start, check
the motor circuit continuity. If the main contacts
don't close, check the control circuit for
Figure
10-10.--Troubleshooting a
3-phase
magnetic
continuity. In the following paragraphs, an
controller.
10-11
