Volt

High Voltage Monitoring Systems Description

The hybrid system monitors several high-voltage components for attempted access. Additionally, a minimum amount of isolation resistance is maintained at all times between both negative and positive poles of the hybrid battery and the vehicle chassis. The drive motor generator power inverter module microprocessors and the hybrid powertrain control module 2 monitor the hybrid system for access and loss of isolation detection.

The High Voltage Interlock Circuit is a wire loop that passes through certain high-voltage components. The high-voltage interlock circuit is used to determine if access to high-voltage components is being attempted. The opening of these high-voltage components causes the high voltage interlock circuit to open. The hybrid system may react to the loss of high-voltage interlock circuit continuity by opening the high-voltage contactor relays and discharging the high voltage capacitors. The high-voltage interlock circuit signal is generated by the hybrid powertrain control module 2. The high voltage interlock circuit status is monitored by the hybrid powertrain control module 2, the hybrid powertrain control module and each drive motor control module.

The hybrid system monitors the electrical potential between high- voltage and the vehicle chassis. High voltage should always be isolated from the vehicle chassis by a certain amount of resistance to avoid the potential for a life threatening current path. In the event that a high voltage leak path is detected to the vehicle chassis, the hybrid system will set a diagnostic trouble code (DTC). High voltage DC chassis isolation is monitored by the motor control modules and the hybrid powertrain control module 2.

Testing for loss of isolation requires special tools and procedures. Because of the high voltages present in the hybrid system, a loss of isolation may occur due to insulation breakdown. Insulation breakdown typically occurs only when high voltages and/or current is present. Conditions such as insulation breakdown cannot be diagnosed with a typical DMM because high voltage is not used by the DMM when measuring resistance.