Hydraulic Pump Circuit.

TM 10-3930-631-34

induced current flows from the forward coil to terminal

must pick up, and there must be a reduction in the

HY1-7 of the diode suppressor module and out terminal

control cycles from approximately the normal 300 Hz to

HY1-6 back to the normally closed reverse interlock

the plugging 3 to 50 Hz. The serverity of the plugging

contact (terminal designation S4-4). Conversely, when

mode is determined by the setting of the plugging

the reverse coil is de-energized, current flows from the

potentiometer.

reverse

coil to the terminal HY1-7 of the diode

(2) The plugging circuit is from the cathode of

suppressor module and out terminal HY1-8 back to the

D2 armature (plugging) diode, and through the bus bar

normally closed forward interlock contact (terminal

to the Al terminal of the static panel. The path continues

designation S3-4). These circuits provide a path to

through Al and A2 drive motor armature terminals, and

dissipate induced current and suppress

voltage

through static panel A2 terminal back to the anode of D2

whenever a directional coil is de- energized.

diode. When the plugging relay contacts close, due to

(5) After a directional coil is energized, all

the induced current, the circuit path for the plugging

circuits between the speed and inching potentiometers

relay is from terminal P1-10 of the control circuit module,

and the P1-5, P1-20, P1-7, and P1-15 terminals of the

through P3-2 of plug P3, the now closed plugging relay

control circuit module become energized. As the

contacts, and back through P3-1 of plug P3 to terminal

resistance of the speed potentiometer is increased

P1-17 of the control circuit module.

g. Hydraulic Pump Circuit.

(accelerator pedal depressed), the resistance of the

speed potentiometer circuit within the control circuit

(1) With the key switch in ON position, the

module increases to cause greater on time of the

operation of any of the parallel pump contacts will

control.

energize the pump contactor coil. Current flows from

(6) After the forward contactor coil is energized,

the positive side of the battery through the power fuse,

current will flow from the positive side of the battery

F2 15 amp control fuse, contactor panel terminal P5-8,

through the power fuse, the now

closed forward

key switch and the now closed pump contacts and

directional contacts, S2 and S1 motor field terminals,

thermal relays to contactor panel terminal P6-3. From

normally closed reverse directional contacts, and Al and

terminal P6- 3, current flows through the pump contactor

A2 drive motor armature terminals to A2 terminal of the

coil and terminal P6-4 to the negative side of the

static panel. From the A2 terminal, current flows to the

battery. A set of normally open pump contactor contacts

A2 terminals of the power switch modules. To complete

now closed to complete the circuit for the pump motor.

the circuit, current flows out of the power switch module

This allows current to flow through the pump motor and

B- terminals to the B- terminal of the static panel, and

from there back to the negative side of the battery.

(2) A hash filter, which is located inside the

(7) As the directional contacts around the drive

diode suppressor module and wired in parallel with the

motor field change position, current will also flow from

pump coil, is used to suppress voltage spikes whenever

the now closed directional contact through a 15 amp

the pump coil is de-energized. At the instant the pump

fuse, D3 and D4 diode (depending upon which direction

coil is de-energized, induced current flows from the

was selected), and R1 resistor to terminal P5-4 current

negative side of the pump coil (K3-2) to terminal HY1-4

flows through terminal P2-11 of plug P2 to the static

of the diode suppressor module. The current path

panel and back to the negative side of the battery. At

continues through the hash filter inside the module and

this same time, control current flows from P1- 2 terminal

out module terminal HY1-3 to the positive side of the

of the control circuit module to the S1 terminals of the

pump coil (K3-1).

h. Power Steering Circuit.

drive regulator modules. To complete the circuit,

current flows out of the B- terminals of the drive

(1) The power steering pump is energized by

regulator modules through the B- terminal stud to the

closing the key switch, emergency cutout switch and

negative side of the battery.

seat switch to complete the power steering circuit. The

f. Plugging Circuit.

current path is from the positive side of the battery

(1) If the lift truck is moving, the accelerator

through the power fuze, F2 15 amp control fuse,

pedal is released, the forward and reverse level is

contactor panel terminal P5-8, key switch, to contactor

moved from one direction to the opposite direction, and

panel terminal P6-10. From terminal P6-10, the path

the accelerator pedal is depressed again, the motor field

continues through the emergency cutout contactor coil

is reversed. To accomplish a plugging mode, the

and terminal P6- 4 to the negative side of the battery.

directional lever must move through its neutral position,

Current flows from the positive side of the battery

the plugging relay

through the 35 amp fuse, and through the ar-

9-7