TM 55-2210-223-12
TO 45A2-2-14-41
1-13. TRACTION MOTORS AND SWITCHING DEVICES (cont)
(2) WHEEL SLIP RELAY (WSR). When a pair of wheels slips, the relay is energized which, in turn, deenergizes the
shunt field and battery field contactors and removes the excitation from the main generator. When the slipping
stops, the engine speed returns to the former setting.
(3) TRACTION MOTORS. The traction motors are direct current series type. One side of the motor is supported by
bearings on the locomotive axle and the other side by a suspension nose cast on the motor and supported on the
truck frame cross tie. Each motor is connected to its axle through a single set of gears.
(4) REVERSER SWITCHES (RVF1, RVF2, RVR1, AND RVR2). The reverser switches control the direction of the
traction motors for forward or reverse motion of the locomotive by changing the direction the current flows through
the traction motor fields. The switches are divided into two sections, one carrying low-voltage battery current for the
interlock circuits, and the other high-voltage current for the traction motors.
(5) REVERSE RELAY (RER). The reverse relay energizes the coil circuits of the power contactors and reverser
switches when the reverser handle is set to FORWARD.
(6) FORWARD RELAY (FOR). The forward relay energizes the coil circuits of the power contactors and reverser
switches when the reverser handle is set to FORWARD.
(7) MOTOR CUTOUT SWITCH (MCO). Controls the coil circuits of the power contactors. It serves to cut out both
motors of either truck for emergency operation in the event that one or both motors on a truck develop trouble.
(8) GROUND RELAY (GR). The ground relay is provided to detect grounding that develops between the traction motor
power circuits and the locomotive frame. When current flows through the ground relay trip coil, it activates the relay
and energizes the holding coil. This action lights the ground warning light, deenergizes the engine run relay and the
battery field and shunt field contactors, and removes the excitation from the main generator. The diesel engine
speed returns to idle. The relay can be reset by moving the throttle to IDLE and pressing the GROUND RESET
button.
1-13
