Effects of Motor Bench System Characteristics on Motor and Inverter Efficiency Measurement Using a Precision Wide-Band Power Analyzer

Motors are evaluated in bench systems, but the impedance characteristics of these systems often differ from those of actual applications due to variations in cable length. Such discrepancies can lead to different voltage and current ringing phenomena, affecting power loss. Therefore, accurate measurement of power loss at ringing frequencies is necessary to evaluate motor efficiency correctly. In this study, a precision wide-band power analyzer with phase compensation was used to accurately measure high-frequency, low-power-factor ringing loss. The effect of ringing loss above 500 kHz on motor loss was 7.4%. Ringing loss in a motor across various cable lengths, switching frequencies, and DC bus voltages was also quantified. Moreover, a method for estimating ringing frequency, which is an important factor when choosing a power analyzer in a motor inverter system with various cable lengths, was proposed.