ASE L3 cheat sheet

High voltage is defined as greater than 60 V DC or 30 V AC RMS; circuits below these limits are not considered shock-hazardous under normal dry conditions.

Effects of 60 Hz current through the body: about 1 mA perception, 10–15 mA let-go threshold, 50 mA pain and respiratory distress, above 100 mA risk of ventricular fibrillation.

Class 0 rubber insulating gloves are rated 1,000 V AC / 1,500 V DC; air-test before each use and electrical retest every 6 months.

Use CAT III meters and probes rated at or above the bus voltage; prove the meter on a known live source before and after the zero-voltage verification.

ECE R100 isolation minimums: 100 ohms per volt for DC buses and 500 ohms per volt for AC buses, measured between live parts and chassis.

Minimum PPE for energized HV work: Class 0 gloves with leather protectors, arc-rated face shield, nonconductive footwear; remove jewelry and metal watchbands.

De-energization sequence: power down, disconnect the service plug or manual disconnect, wait the specified discharge time (commonly 5–10 minutes), verify 0 V at the inverter terminals, then lock out and tag.

The High Voltage Interlock Loop is a low-voltage series circuit routed through every HV connector; opening any connector breaks the loop and commands the contactors open. Never jumper an HVIL.

Orange cable and orange connectors identify HV conductors; do not cut, crimp, splice, or probe through insulation.

Typical lithium-ion cell voltages: nominal 3.6–3.7 V, full charge 4.1–4.2 V, discharge cutoff about 3.0 V (LFP cells use roughly 3.2 V nominal and 3.65 V full).

Pack energy in kWh = nominal pack voltage × capacity in Ah ÷ 1000; cells in series add voltage, cells in parallel add capacity.

State of charge estimation fuses coulomb counting for short-term accuracy with open-circuit-voltage lookup and temperature compensation for long-term correction.

Internal resistance rises at low temperature and with age; the BMS derates charge and discharge power limits accordingly.

An isolation fault is detected by the insulation monitoring device; a reading below 100 ohms per volt DC sets a DTC and may open the contactors. Do not clear the code without locating the fault.

Passive balancing dissipates energy from the highest-voltage cells through resistors; active balancing transfers charge between cells with higher efficiency.

The thermal management loop normally holds the pack between about 15 °C and 35 °C; a cell-to-cell delta above 5–10 °C suggests a coolant flow or sensor problem.

Thermal runaway indicators: self-heating with no load, cell swelling, sweet or solvent odor, venting, and arc tracking on bus bars.

The precharge resistor limits inrush current into the inverter DC-link capacitors; a welded contactor shows bus voltage present with the key off.

Back-EMF = k_e × speed and torque = k_t × current; both constants are set by rotor magnet flux, so they scale together.

Field weakening injects negative d-axis stator current to oppose magnet flux, extending operation above base speed at approximately constant power.

The inverter converts DC bus voltage into three-phase PWM at roughly 8–20 kHz; the DC-link capacitor smooths ripple and retains lethal charge after shutdown.

Regeneration occurs when rotor back-EMF exceeds DC bus voltage; the anti-parallel diodes rectify and current flows back to the pack.

Motor phase resistances should match within a few percent; a large imbalance indicates a shorted turn, a poor weld, or a bad connection.

Insulation-test the stator to ground at the manufacturer-specified voltage (often 500 V DC); never apply a megohmmeter to the inverter or its semiconductors.

Resolver or encoder faults cause torque loss, rough operation, or runaway; verify excitation, sine amplitude, and cosine amplitude.

Silicon carbide MOSFETs switch faster and tolerate higher junction temperatures than IGBTs, reducing switching loss and cooling demand.

Desaturation protection in the gate driver detects device overcurrent and turns the switch off in microseconds to prevent rupture.

Power in kW = torque in N·m × speed in rpm ÷ 9549; power in hp = torque in lb·ft × rpm ÷ 5252.

Hybrid control typically keeps state of charge between about 20% and 80%; EV usable windows are roughly 10–90% with buffers at both ends.

Equivalent consumption minimization converts electrical energy into an equivalent fuel cost with a multiplier, then minimizes total equivalent fuel over the trip.

High-speed CAN is commonly 500 kbit/s with 120-ohm terminators at each end; a healthy bus measures about 60 ohms across CAN-H and CAN-L.

Torque arbitration splits driver demand among engine and motors using efficiency maps, SOC, temperature, and component power limits, then broadcasts torque commands on CAN.

Precharge sequence: close the precharge contactor, wait until DC-link voltage reaches about 95% of pack voltage, then close the main positive contactor.

Regenerative capability is reduced or disabled at very high SOC, low pack temperature, or when the charge power limit is low.

Electric motor torque responds in roughly 10 ms versus hundreds of milliseconds for an engine, so controls apply torque-rate limiting and filtering for drivability.

Available regen torque is the minimum of battery charge power limit, motor torque limit, stability-control request, and SOC headroom.

Blending rule: total brake demand = regenerative torque + friction torque; friction makes up any deficit at low speed or high SOC.

Below roughly 5–10 km/h regenerative torque cannot be sustained, so the controller fades regen out and phases friction braking in to hold pedal feel.

When ABS or ESC becomes active, regenerative torque is ramped down within tens of milliseconds to avoid wheel-slip oscillation.

Kinetic energy available for recovery is ½ × mass × velocity²; round-trip recovery efficiency from wheel to pack is typically 60–70%.

One-pedal calibration: accelerator lift commands negative torque up to about 0.2–0.3 g deceleration; friction brakes hold the vehicle at standstill and brake lamps trigger above a decel threshold.

Regen is unavailable with a cold or fully charged pack; the driver must be informed because deceleration feel changes even though hydraulic braking remains intact.

Wheel speed sensors, brake pressure sensors, and the brake pedal travel sensor all feed the regenerative blending controller.

Electric A/C compressors use a three-phase permanent-magnet motor with an integrated inverter, operating from 200–400 V DC; no HV present means no refrigeration.

Positive temperature coefficient heaters are HV-powered and self-limiting, since resistance rises with temperature; coolant-type and air-type versions both exist.

A heat pump delivers a coefficient of performance of roughly 2–4, while resistive heating is about 1.0, so cabin heating strategy strongly affects range in cold weather.

The onboard charger converts AC to DC at 3.3, 6.6, 11, or 22 kW, performs power factor correction, monitors isolation, and negotiates with the EVSE.

SAE J1772 control pilot is a 1 kHz PWM signal; duty cycle encodes the available current and voltage levels encode vehicle state.

DC fast charging uses an off-board charger; the vehicle performs the handshake, verifies isolation, and closes contactors before current flows (CCS, CHAdeMO, GB/T, NACS).

The DC-DC converter steps HV down to 12–14 V at roughly 1.5–3 kW to maintain the auxiliary battery; its failure will strand the vehicle even with a charged traction pack.

Charging inlets carry a temperature sensor and an interlock; overheating usually indicates high contact resistance at the pins or terminals.

HV accessories share the pack isolation monitoring, so a heater or compressor ground fault can disable the entire high-voltage system.