Bypass Circuit With Shunt Field Activated

Current In Relation To Time

The logics monitors the current that flows through T1D, T2D and T3D and limits this current flow to a preset value. As this current flows through T1D, T2D and T3D, the drive motor and the current sensor, a voltage is created by the sensor. This voltage is proportional to the current flowing through the sensor and will increase or decrease as current changes. The logics uses this voltage to monitor the current in the circuit. When the current has increased too high, the logics decreases the pulse rate to the transistors to prevent current higher than the preset value.

Thermal Protection Circuits

Control Panel

If the power transistors overheat, heat is transferred to a thermal switch mounted in a common heatsink. The thermal switch will open at a predetermined temperature. When it opens, voltage at logics connection P2-2 will go HIGH (15 volts). The instrument panel will display a “Run Time” diagnostic symbol. The logics will decrease the current limit setting of the drive system and the hydraulic circuit pulsing to 50%. The amount of current allowed to flow through the power transistors is decreased to allow them to cool. When the heatsink cools off and the thermal switch closes, the truck will return to normal operation. Drive system bypass and hydraulic pump contactor operation are not affected by an overheated control panel. NOTE: Standard thermal protection is provided when programmable feature “3” (Thermal Shutdown Selection) is set to “0” (not enabled). Setting the feature at “1” will cut back pump motor speed under thermal indications from either the control panel or the pump motor. Setting the feature at “2” will cut back pump motor speed under thermal indications from the control panel, the pump motor or the drive motor.

Drive Motor

If the drive motor overheats, a thermal switch mounted in the drive motor housing will open at a predetermined temperature. When it opens, voltage at logics connection P2-3 will go HIGH. The instrument panel will display a “Run Time” diagnostic symbol. To decrease the amount of current allowed to flow through the drive motor, the logics will reduce the current limit setting and disable the bypass contactor. When the drive motor cools and the thermal switch closes, the truck will return to normal operation.

Hydraulic Pump Motor

If the hydraulic pump motor overheats, a thermal switch mounted in the pump motor housing will open at a predetermined temperature. When it opens, voltage at logics connection P2-1 will go HIGH. The instrument panel will display a “Run Time” diagnostic symbol. To decrease the amount of current allowed to flow through the pump motor, the logics will restrict the hydraulic pump motor to 50% pulsing and disable the pump contactor. When the hydraulic pump motor cools and the thermal switch closes, the truck will return to normal operation.

Failure Protection Circuit

If the logics detects an improper voltage at P12-6 wire #37 (drive circuit), P12-7 wire #45 (pump circuit), P12-4 wire #71 (pump shunt field circuit) or P12-9 wire #92 (drive shunt field circuit), the line contactor will be deactivated and a “Run Time” diagnostic code (display = F2 through Fb) will replace the BDI indication. Once a failure has been detected, the truck must be repaired before normal operation can resume.

The bypass circuit bypasses T1D, T2D and T3D