alternating-current, for 60 seconds to
this motor may act as a brake and try to
ground.
keep its axle from turning. Check figure
b. Old Equipment. On equipments which have
been in service, it is not considered necessary or
h. In correcting any of the above troubles check
advisable to apply the same insulation tests as on new
with the locomotive diagram, figure 44, and correct the
equipments and the following tests are commonly used:
circuit at the proper point. This will avoid future
confusion caused by the locomotive wiring not agreeing
(1) Main circuits 800 to 1,000 volts, ac, 60
with the diagram.
seconds.
(2) Control circuits 500 volts, ac, 60 seconds.
52. Insulation Tests
a. New Equipment.
Caution
(1) The main generator armature circuit,
On locomotives equipped with
including the commutating field, and the
ground relays, open the ground relay
traction motor circuits and apparatus
cutout breaker before applying
connected thereto, when assembled on a
insulation tests to the main circuits.
new equipment should withstand an
insulation test of 1,800 volts, alternating
c. Insulation Resistance. When locomotives are
current, for a period of 60 seconds to
placed in service, the insulation resistance of the power
ground.
circuits of the generator and traction motors should be at
(2) All control and auxiliary generator circuits,
least 1 megohm. If moisture and conducting particles
and apparatus connected thereto except
have affected the insulation resistance before the
meters and storage battery on new
locomotive is placed in service, this circuit should be
equipment should withstand 800 volts,
thoroughly dried out by running at light load and low
engine speed and rechecked for insulation resistance.
Section V. TROUBLESHOOTING
53. General
b. Failure of Contactors to Close. If fuses are
good and battery is charged, check for open circuits in
a. A general study of this manual and the actual
the control wiring. Also check the contacts on the push
equipment will enable the operator to diagnose and care
button.
for many minor cases of trouble. Some troubles can be
corrected by the operators but some obviously have to
c. Starting Switches Close but Engine does not
be remedied by the maintainers.
In general the
Start. Check for open circuit in wiring, inspect switch
equipment should not be operated under conditions that
contacts and fuse.
will result in serious damage to parts. Correct all
troubles promptly to obtain the longest life of all parts.
55. Falling Off of Power
b. If the purpose and proper function of each part
a. A decrease in engine power should become
of the equipment is learned it will assist in the quick
manifest to the operator by failure to obtain the usual
location and remedy of trouble.
speed with a given load on a given part of the run, or by
character of engine noise or by meter indication.
54. Generator Fails to Crank Engine
b. The falling off of power may be due to engine
If instructions for starting the engine have been
conditions. For possible remedies, refer to TM 55-1046
observed and the engines fail to start, the trouble may
and TM 55-1046-1.
be due to the following:
a. Low Battery Voltage. This is indicated by failure
56.
Loss of Power Indicated by Overspeeding of
of the starting contactors to close or by failure of the
Engine
starting motor to bring the engine up to firing speed;
a. May be due to failure of the field contactors to
check battery charge and examine for corroded
operate properly. Check for open circuits in wiring or
terminals.
poor or dirty or corroded contacts on switches.
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