Abstract : The waveforms of general-purpose frequency inverters are chopper waveforms, and PWM waveforms are the most common waveforms. This results in high-order harmonics in the input and output of the inverter, making it impossible to accurately measure the output power of the inverter at low frequencies. This paper introduces a method for measuring the output power of the frequency inverter by simulating its analog output, and then calculating the efficiency of the variable frequency motor. Keywords : frequency inverter, variable frequency motor, variable frequency motor efficiency, power, power factor [b][align=center]Method for Measuring the Efficiency of Variable Frequency Motor Zhang Yulin and Rongbin[/align][/b] Abstract : For a common inverter, the wave form is chopper, and PWM is the most common wave form - thus the high-order harmonics exist in the input and output wave of it. Under the condition of low frequency - the output cannot be measured exactly. This paper introduces how to measure the output of the inverter by simulating its quantity - and the method for calculating the efficiency of variable frequency motor. Keywords : Inverter, variable-frequency motor, efficiency, output-power factor. 0 Introduction The output power of an inverter is equal to the input power of a variable-frequency motor. Therefore, to measure the efficiency of a variable-frequency motor, it is necessary to measure both the output power of the motor and the inverter. The output power of the variable-frequency motor can usually be calculated from the torque and speed values ​​measured by a torque-speed sensor. However, because the output side of the inverter contains high-order harmonics, using a current transformer for ease of measurement may lead to current transformer saturation, especially at low frequencies. Using a common current transformer, the output power of the inverter (the input power of the variable-frequency motor) cannot be accurately measured, and therefore the efficiency of the variable-frequency motor cannot be accurately measured. To solve this problem, the following test method is introduced. [b][align=center]For details, please click: Test Method for Variable-Frequency Motor Efficiency[/align][/b]