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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.
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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.
DC isolation fault detection measures DC leakage to chassis ground.
AC isolation fault detection injects an AC signal onto the bus.
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.