EMC testing for EV chargers: how to prepare and pass the first time

#Which standard applies

IEC 61851-21-2 covers off-board equipment with rated input and output voltages up to 1000 V AC or 1500 V DC, in residential, commercial and industrial environments, indoors and outdoors. Passive cables without electronics are deemed compliant without testing.

#What is tested

Emissions — what the charger sends out:

• conducted disturbances on the AC mains and, where relevant, on signal and DC ports,
• radiated disturbances,
• for AC-connected equipment, harmonic currents and voltage fluctuations (flicker).

Immunity — how the charger copes with disturbances:

• electrostatic discharge,
• radiated and conducted radio-frequency fields,
• electrical fast transients and surges,
• power-frequency magnetic fields,
• voltage dips and short interruptions.

For each immunity test, the charger must meet a defined performance criterion: keep charging normally, recover by itself, or at least fail safely.

#Prepare these before the lab date

1. Operating modes. Agree which modes are tested: standby, charging at rated power, charging at low power, and communication without power transfer.
2. Load. DC chargers need a DC load or battery emulator that can absorb rated power; AC chargers need a vehicle simulator. Check that the load does not create its own noise.
3. Monitoring. Decide how the lab sees that the charger still works: power output, control pilot and proximity signals, CAN or PLC communication, the display and the backend connection.
4. Performance criteria. Write down what counts as a failure for each test. Disputes during testing usually come from criteria nobody defined.
5. Configuration. Freeze hardware, firmware and cable routing. A late change invalidates earlier results.

#Design points that save a retest

• Keep the input filter close to the cable entry and give it a short, wide earth connection.
• Route power and signal cables apart; shield communication lines and terminate the shield at the entry point.
• Check the enclosure joints and openings on metal housings; gaps near the power stage act as slot antennas.
• Run a pre-compliance scan of conducted and radiated emissions on the first prototype.

Our partner laboratory network runs full EMC testing for chargers in a 10-metre semi-anechoic chamber rated AC/DC 2.5 MW, and supports pre-scans during development.