Chapter 3 High-Voltage Vehicle Safety Systems High-Voltage Safety Systems • Interlock Systems • Service Disconnect Services • Isolation Fault Detection Systems
The J1673 standard provides a visual means of identifying high-voltage wires and cables.
A serial interlock loop (SIL) connects each high-voltage device in series.
Each wire that carries high voltage has a serial interlock loop circuit that reports the status to the battery-pack controller.
A local interlock loop (LIP) connects each high-voltage device on a LAN bus.
A grounded switch interlock is a modified LIP system with switches located within its components.
An active bus-discharge circuit is typically located within the power inverter.
The op-amp output voltage in the saturated state is equal to the supply positive voltage. The op-amp output voltage in the low state is approximately equal to the voltage on the op-amp ground.
A window comparator permits the op-amps to sense whether a voltage input is within a specific voltage window.
A high-voltage cutoff switch and an inertia fuel shutoff switch work with the interlock circuit and open in the event of a collision.
The service discon-nect system permits a technician to manually isolate the battery-pack system from other vehicle systems.
An isolation-fault detection system monitors the vehicle chassis ground to determine if high voltage is acquiring an electrical path to the chassis.
The voltage-sensing stage monitors the voltage on both the analog and chassis grounds.
The differential-amplifier stage amplifies the difference between its inverting and non-inverting inputs.
The voltage-comparator stage senses voltages and compares those voltages to a voltage reference value.
The controller uses logic to determine whether a voltage level is within a safe range.
A simple voltage-regulator circuit can be constructed with zener diodes, resistors, and capacitors in parallel and one resistor in series.