Specifications

BASICS OF CIRCUIT OPERATION

The control circuit is energized by closing the key switch, seat switch, and moving the for-

ward or reverse lever to either position, and then depressing the accelerator closing the start switch.

This applies power to the control card turning on the PMT driver , which will close the selected

directional contactor and complete the circuits to the drive motor. (See elementary drawings.)

The control card then supplies a gate pulse to 2REC turning it on to a conducting state,

allowing current to flow from the battery through lC, lX, 2REC, motor field, motor armature, sensor,

and back to the battery. After lC charges, 2REC shuts off due to lack of holding current. The con-

trol card checks that lC is charged and unlocks the gate to lREC and 5REC.

The control card then supplies a gate pulse to lREC turning it on to a conducting state, allow-

ing current to flow from the battery through lREC, motor field, motor armature, sensor, and back to

the battery. 5REC turns on and allows current to flow T4-T3, lC, lREC, 5REC to T4-T3. This

current charges the bottom of lC positive with respect to the battery positive bus. This charging cycle

occurs in less than l millisecond (.00l sec.) and 5REC shuts off. This charge is now stored on the

capacitor until it is time to turn off lREC.

Current continues to flow in lREC until the control card fires 2REC. When 2REC conducts,

capacitor lC discharges around the circuit composed of lC, 1X, 2REC, and lREC. This discharge

current opposes the battery current through lREC so that the resultant current is zero. With reverse

voltage across lREC, lREC is turned off. Current continues to flow in the 2REC, lC, motor and

battery loop until the capacitor (card terminal l4) is fully charged negative. This charge exceeds

battery voltage by an amount which is a function of peak motor current, and 2REC turns off. Figure l

illustrates the pulsing of current from the battery.

Figure l Figure 2

During the off time, the energy stored in the motor, by virtue of the motors inductance, will

cause current to circulate through the motor around the loop formed by 3REC. Thus, providing MD=J