Operation - TM-10-3930-631-340119

TM 10-3930-631-34

from the positive side of the battery through the 400

provide additional inputs to the contactor logic to open if

amp power fuse, the closed forward contactor contacts

an improper condition is detected.

to the drive motor. When the drive motor operates, the

(4) The power switch and drive regulator

truck moves in the direction selected.

modules regulate operation of the drive motor through

(4) The forward and reverse contactors are

the armature and free wheeling diodes.

equipped with interlocks to prevent current flow to both

(5) The plugging circuit and plugging relay

sides of the drive motor simultaneously. The interlocks

reduce the control cycles to prevent damage to the

are mechanically operated whenever the applicable

control and motor when direction of travel is reversed.

contactor opens or closes.

(6) The

temperature

coefficient

resistor

(5) The hydraulic pump contactor (fig. 2-7)

monitors the temperature of the control heat sink. When

operates in much the same manner. With the key

temperature rises excessively the resistor will reduce

switch, seat switch and emergency cutout switches

the on time of the power switch module .

closed, movement of the control valve levers will close a

(7) Additional safeguards are supplied by four

pump switch. Current then flows from the positive side

thermal relays. If the operating temperature of the drive

of the battery through the 400 amp power fuse, 15 amp

motor rises above a safe operating point, the thermal

control fuse, to the contactor panel and the pump con-

relay will open and halt motor operation. After allowing

tactor coil to the negative side of the battery. A set of

the relay to cool the points will close and operation can

normally open contacts on the pump contactor close

be resumed.

and send current to the pump motor. Current flows

(8) Another thermal relay protects the hydraulic

through the pump motor back to the negative side of the

pump motor in the same manner. Two thermal relays

battery.

monitor the temperature of the hydraulic oil in the

(6) The contactor panel also contains the diode

reservoir and will shut down the hydraulic pump circuit if

suppressor module. The suppressor module contains

the temperature becomes too high.

hash filters to suppress voltage spikes

when the

9-3. Operation

hydraulic pump coil, horn button, contactor coils and

a. General. The following is a more detailed

hourmeter are de-energized.

description of the control operation. By using the wiring

(7) All fuses are mounted in the contactor

diagram (fig. 9-1) and the block diagram (fig. 9-2) the

panel. The four 15 amp control fuses are mounted in

operation can be followed in detail. The points below are

the upper left corner of the contactor panel.

general and will aid in understanding the operation.

e. Static Panel

(1) Any connections, junctions or terminals with

(1) The static panel (fig. 9-6) is mounted in a

the same identification are electrically common.

compartment on the left side of the frame. For easy

(2) All contacts and components are illustrated

access the panel is mounted on a hinged door. When

(fig. 9-1) in a normally de-energized condition unless

the door is opened and swung down into place, the

otherwise specified.

static panel components are accessible for maintenance

(3) Location of components on the schematic

procedures.

diagram will have no bearing on their physical location

(2) Mounted on the static panel are the control

within the fork lift truck.

circuit module, three power switch modules, three drive

b. General Operation.

regulator modules, the plugging relay and three large

(1) The basic time-ratio control is a fixed-

capacitors. The armature diode and free wheeling diode

frequency type. The frequency is non-adjustable and is

are mounted in the front portion of the static panel. A

approximately 300 Hz. The on time of the control, which

positive temperature coefficient resistor is mounted in

is determined by the position of the

speed

the heat sink.

potentiometer, is controlled by the operator's accelerator

(3) The control circuit module sends the current

pedal. The on time is controllable from zero to 100 %

through the power switch and drive regulator modules.

(fig. 9-4).

Circuits within the module

9-5