f. Auxiliary Generator Ammeter.
These are
circuit. It is provided with voltage coils
and a current coil for reverse-current
connected to measure the output of each auxiliary
protection. It closes the circuit when the
generator.
auxiliary generator voltage reaches a
predetermined value above battery
connected to measure the battery charge and discharge
voltage.
current.
e. Voltage Relay. Relays T1 (and T2) measure
h. Engine Shutdown Valve. Energizing the coil of
main generator voltage and automatically control the
the engine shutdown valve will stop the diesel engine.
shunt field motor connections. Relays ES1 (and ES2)
i. BS Contactor.
This contactor places the
measure main generator voltage and commutate a step
batteries in series for engine starting.
of resistance in the self-excited field of the main
j. BP Two Pole Contactor. This contactor places
generator. In this manner, proper engine loading is
the batteries in parallel for charging.
obtained over the current range of the generator.
k. Battery Signal Lamp. This light is lit whenever
the battery switch and the two pole contactor are closed.
16. Traction Motors and Switching Devices
It, therefore, burns whenever the batteries are in the
a. Traction Motors.
The traction motors are
parallel connection.
geared to the driving axles. They are self-ventilated.
l. Battery Relay Panel.
b. Traction Motor Contactors. Magnetic contactors
(1) This relay panel eliminates the need for
P1, P2, etc., connect the motors in the parallel
fuses in the series-parallel battery circuit.
combination.
If the BS contactor and the BP two pole
c. Field Shunt Contactors. Magnetic contactors
contactor were closed at the same time,
M1, M2, etc., connect the field shunt resistors in parallel
the batteries would be short-circuited.
with the motor fields. This results in better performance
However, the short circuit current would
at higher locomotive speeds.
flow through the operating coils of the
d. Reverser.
The electro-pneumatic reversers
battery relay and pick the relay up, thus
change the connection between the motor fields and the
dropping out the BP two pole contactor
armatures for forward or reverse motion of the
.and opening the short circuit.
The
locomotives.
holding coil of the relay then holds the
relay in until the battery switch is opened.
17. Miscellaneous Devices
When the battery switch is opened, the
a. Controller. The controller has two handles with
relay will drop out, allowing the BP two
which the direction and speed of the locomotive are
pole contactor to reclose. However, if the
controlled. The controller is interlocked to prevent
cause of the short circuit is not removed,
movement of the reverser handle while the throttle
the relay will again pick up as soon as the
handle is in running notch.
battery switch is closed.
b. Pushbuttons. These are provided for starting
(2) The battery signal lamp is extinguished
whenever the battery-relay picks up and
the diesel engines.
remains extinguished until the relay is
c. Control Circuit Breaker. This circuit breaker
dropped out.
supplies power from the battery for all control circuits
m. Ground Relay.
except the auxiliary generator field circuits.
(1) The ground relay GR has four contacts
d. Auxiliary Generator Circuit Breaker. This circuit
and two coils, a trip coil and a holding coil.
breaker controls the auxiliary generator field circuits. It
When the ground relay picks up, it
must be closed during all operating periods.
performs
the
following
functions:
e. Main Circuit Shunts and Ammeters. These
energizes the ground relay holding coil;
provide meter indication of the main generator load
lights the ground warning light; opens the
current. The ammeter has a colored band dial showing
P contactors, removes the main generator
various load time limits and also an ampere scale.
excitation and reduces the diesel engine
speed to idle.
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