Figure 1-24-Troublesboottng a 3-phase magnetic tine starter.

the dc brake construction is of solid metals and requires

no lamination as does the ac magnetic brake.

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, smell of burning insulation, and so

on.) occur, the cause of the trouble can be found by

conducting an examination that consists of nothing more

than using the sense of feel, smell, sight, and sound. On

other occasions, however, locating the cause of the

problem will involve more detailed actions.

Troubles tend to gather around mechanical moving

parts and where electrical systems are interrupted by the

making and breaking of contacts. Center your attention

in these areas. See table 1-1 for a list of common

troubles, their causes, and corrective actions.

When a motor-controller system has failed and

pressing the start button will not start the system, press

the overload relay reset push button. 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, then

check the motor circuit continuity. If the main contacts

do not close, then check the control circuit for continuity.

Figure 1-24-Troublesboottng a 3-phase magnetic tine starter.

An example of troubleshooting a motor-controller

electrical system is given in a sequence of steps that may

be used in locating a fault (fig. 1-24). We will start by

connections within the controller. However, if voltage

analyzing the power circuit.

is indicated at all three terminals, then the trouble is

either in the motor or lines leading to the motor.

POWER CIRCUIT ANALYSIS

CONTROL CIRCUIT ANALYSIS

When no visual signs of failure can be located and

an electrical failure is indicated in the power circuit, you

must first check the line voltage and fuses. Place the

Suppose the overload reset buttons have been reset

voltmeter probes on the hot side of the line fuses as

and the start switch is closed. If the power contacts do

shown at position A. A line voltage reading tells you that

not close, then the control circuit must be checked. The

your voltmeter is operational and that you have voltage

testing procedure is as follows:

to the source side of the line fuses, L1-L2. You also may

1. Check for voltage at the controller lines, L1, L2,

check between L1-L3 and L2-L3. To check the fuse in

and L3.

line L1, place the voltmeter across the line fuse as shown

2. Place the voltmeter probes at points C and D

at position B between L1-L2. A voltage reading shows

(fig. 1-24). You should have a voltage reading when the

a good fuse in L1. Likewise, check the other two fuses

stop switch is closed and a no-voltage reading when the

between L1-L3 and L2-L3. A novoltage reading would

stop switch is open. The conditions would indicate a

show a faulty fuse.

good stop switch.

If the line fuses check good, then check the voltage

between terminals T1-T2, T2-T3, and T1-T3. The

3. Next, check the voltage between points C and

E. If you get a no-voltage reading when the start switch

controller is faulty if there aren't voltmeter readings on

is open and a voltage reading when the start switch is

all three of the terminal pairs, and you would then

closed, then the start switch is good.

proceed to check the power contacts, overloads, and lead

1-18