42 March/April 2025 | E-Mobility Engineering Peter Donaldson examines various means of testing electric motors The mechanical heart Although mechanically simple, compared with internal combustion engines, the electric motors forming the heart of the propulsion system of EVs of all kinds must go through intensive testing. This involves the use of many technologies and procedures to probe performance, efficiency, reliability and safety at every stage of manufacture and integration. During manufacture, electrical testing starts fairly early on in the process: verifying the integrity of insulation under high voltage, measuring the resistance of windings to ensure they are uniform and falling within the specified tolerances. Then both surge testing and partial discharge testing that, can detect short circuits, weaknesses and early-stage faults with the insulation of windings. Mechanical testing at this stage focuses on key areas such as dimensional measurement as a quality control check on casting and machining rotors and stator housings, along with balancing rotors to ensure smooth operation. This is essential to reduce the risk of damage to bearings, insulation and connections from vibration, and knock-on effects to systems coupled to the motor. This is complemented by thermal testing, using infrared cameras to check for hotspots in operation. End-of-line (EoL) testing includes functional runs that replicate the operational conditions that the motor is intended to face, validating torque output and rotational speed (from which power is calculated) along with efficiency. Manufacturers also analyse noise, vibration and harshness during EoL testing as a quality assurance check. System-level tests When the motor is integrated into its intended powertrain, the combined system must face a new set of tests, which involve additional components, and emphasise system-level performance plus different parameters and stressors. Powertrain dynamometers are used to measure torque, speed and power across the full operational range, and the duty cycles they are designed to face, while inverter-motor testing systems are used to evaluate interaction between the motor and its power electronics. Thermal and cooling system testing is Pictured in an anechoic chamber, this eSmart is instrumented with an IMC data acquisition system including the WFT-Cx wheel force transducer and GRAS measurement microphones to test its powertrain (Image courtesy of IMC)
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