ASE L3 key terms

A low-voltage loop routed through high-voltage connectors, covers, and service plugs. If any point in the loop opens, the controller opens the battery contactors so exposed high-voltage conductors are de-energized.

A service plug or switch that opens the high-voltage circuit, often splitting the pack into lower-voltage sections. The technician removes it and keeps it under personal control before working on high-voltage parts.

Rubber gloves built and tested to a voltage class, worn with leather protectors whenever high-voltage hardware is handled. They are air-tested before each use and retested on a set schedule.

A test instrument rated for the transient overvoltages found on distribution-level circuits. For vehicle high-voltage work, its CAT rating and voltage rating must exceed the circuit being measured.

A rapid release of energy caused by current flowing through air between conductors. It produces intense heat, light, pressure, and molten metal, which is why circuits are de-energized and PPE is worn.

A formal procedure that isolates every energy source, applies a personal lock and tag, and proves the circuit is dead so equipment cannot be re-energized while someone is working on it.

An instrument that applies a high test voltage to measure insulation resistance between high-voltage conductors and chassis. A low reading points to damaged cable, connector, or component insulation.

The electronic controller that measures cell voltages, temperatures, and pack current, estimates state of charge and health, balances cells, and commands the contactors and thermal system.

The percentage of usable battery capacity currently remaining, much like a fuel gauge. It is estimated from current integration, open-circuit voltage, and temperature rather than measured directly.

How much capacity and power the pack can still deliver compared with when it was new, usually given as a percentage and driven by age, cycling, and temperature history.

A self-accelerating chain of heat-releasing reactions inside a cell that raises temperature and pressure until the cell vents or burns. It can spread to neighboring cells, so packs include barriers and vent paths.

A heavy-duty relay that connects the battery pack to the high-voltage bus. It opens on command, after a crash, or when a fault such as interlock loss is detected.

A resistor, or resistor plus contactor, that lets current trickle into the inverter's capacitors before the main contactor closes, preventing a huge inrush current and welded contacts.

Equalizing charge among series-connected cells, either by bleeding energy from higher cells as heat or by moving charge between them, so the weakest cell does not limit usable pack capacity.

Continuous measurement of resistance between the high-voltage bus and chassis. A value below the manufacturer's threshold sets a fault and may block contactor closure or charging.

A traction motor whose rotor carries permanent magnets and whose speed follows the inverter's output frequency. It is efficient and produces strong regenerative braking torque.

Power electronics that switch direct current from the battery into three-phase alternating current for the motor, and convert motor-generated current back to direct current during regeneration.

A fast, high-power semiconductor switch used in inverter and converter circuits. Modules are often paralleled, need cooling, and require isolated gate drive circuits.

A rotary sensor that reports rotor angle and speed to the motor controller, which needs that information to time the inverter's switching accurately.

A converter that steps high battery voltage down to roughly 12 to 15 volts to run vehicle accessories and charge the auxiliary battery, replacing the traditional alternator.

Rapidly switching a semiconductor on and off to create a variable average voltage. In inverters it shapes the three-phase waveform that sets motor speed and torque.

Six power switches arranged in three legs, each leg connecting one motor phase to either the positive or negative bus to produce the alternating output the motor needs.

The supervisory computer that reads driver inputs and sensor data, then sends torque, charging, and thermal commands to the motor, engine, battery, and brake controllers.

The control process that splits a driver's torque request between the internal combustion engine and one or more electric machines to balance efficiency, emissions, and response.

A planetary gearset that divides engine power between the wheels and a generator, letting a hybrid transaxle behave like a continuously variable transmission.

A hybrid operating strategy that holds battery state of charge near a target by using the engine or regeneration to replace energy as it is used.

The rules or algorithms that decide moment-to-moment power split, engine on/off, and battery use to meet driver demand while optimizing efficiency and emissions.

Using the traction motor as a generator so the vehicle's momentum charges the battery while creating braking torque, recovering energy that friction brakes would release as heat.

Coordinating regenerative and friction braking so total braking matches the driver's request, maximizing energy recovery while keeping pedal feel and stopping distance consistent.

A spring and damper assembly that creates pedal feel when the brake pedal is decoupled from the hydraulics, as happens on some hybrids and electric vehicles during regeneration.

A mode in which lifting off the accelerator applies strong regenerative braking and slows the car toward a stop, so the brake pedal is used mainly for harder stops.

The maximum negative torque the controller will allow, set by battery state of charge, temperature, charge acceptance, and motor speed so regeneration cannot damage the pack.

Regenerative torque must be reduced or removed when ABS or stability control is active, because motor braking acts on the drive wheels and can interfere with wheel-slip control.

A high-voltage air-conditioning compressor with its own inverter and sealed lubricant, driven by electricity instead of a belt, so it can run only when needed.

A resistive high-voltage heater whose resistance rises as it warms, limiting current draw. It heats cabin air or coolant in vehicles that lack engine waste heat.

A reversible refrigerant system that moves heat from outside air or waste sources into the cabin, using far less energy than resistive heating in mild weather.

Equipment inside the vehicle that converts alternating current from a charging station into direct current at the voltage the battery needs, while controlling current and talking to the station.

The off-board charging station, cable, and plug that deliver AC or DC power and use signaling to tell the vehicle how much current is available.

A pulse-width modulated signal on the charging connector that communicates available current, vehicle-connected state, and permission to start charging between station and vehicle.