ISO 21782-3:2019

Overview

ISO 21782-3:2019 defines performance test specifications for the motor and inverter of a voltage class B electric propulsion system for electrically propelled road vehicles. Part 3 of the ISO 21782 series focuses on standardized laboratory procedures to measure losses, efficiency, thermal behaviour, torque characteristics and related performance metrics to verify that a motor/inverter pair meets design and contractual requirements.

Key topics and technical requirements

• Scope and reference: Applies to motors and inverters as part of voltage class B systems; normative references and operating point definitions come from ISO 21782‑1 (general test conditions and definitions).
• Measurement of loss and efficiency:
  • Motor and inverter power measurements may use the two‑wattmeter or three‑wattmeter methods (three‑wattmeter recommended).
  • Test diagrams specify DUT, inverter, load, torque/speed detectors and power meters for repeatable measurements.
  • Operating points follow those defined in ISO 21782‑1; test durations, switching frequency and ambient/coolant conditions are specified.
• Temperature rise tests:
  • Thermal tests for motor and inverter measure temperature at defined points after prescribed operating times.
  • Coolant guidance includes liquid cooling at up to 65 °C (if feasible) and minimum flow requirements.
• Torque characterization:
  • Tests for steady-state torque behavior across defined operating points.
• Cogging torque:
  • For permanent‑magnet motors, low‑speed no‑load measurement of cogging torque waveform and peak‑to‑peak value.
• Inverter-specific tests:
  • Measurement of loss, efficiency and conversion rate using AC loads (actual motor, motor emulator, ACL or RL equivalents).
• Chopper tests and test reporting:
  • Part 3 includes chopper measurement procedures and mandatory elements for test reports (see Annex B).
• Practical measurement guidance in Annex A (precautions for loss and efficiency measurement).

Applications and who uses this standard

• Electric vehicle OEMs and suppliers for contract verification of motor and inverter performance.
• Independent test laboratories and certification bodies performing standardized performance and thermal testing.
• R&D and validation teams evaluating powertrain components during development.
• Procurement and quality assurance to define acceptance criteria for propulsion components.

Related standards

• ISO 21782‑1 - General test conditions and definitions for the ISO 21782 series.
• Other IEC/ISO electrotechnical standards may be referenced for measurement terminology and safety.

By aligning testing to ISO 21782‑3:2019, stakeholders ensure consistent, repeatable evaluation of motor and inverter performance-supporting compliance, interoperability and reliable electric propulsion system development.