Assessment Method For Motor Energy Efficiency Based On Online Monitoring

The most significant component is online assessment of motor operating efficiency in energy efficiency assessment of motor system, that is, input power and output mechanical power of motor is utilized to solve the real-time operation efficiency. The input power can be immediately obtained using measured terminal voltage and current of motor. However, in most actual occasions, the output mechanical power cannot be directly measured for the reason that there isn’t measuring equipment of torque and speed. Therefore it’s significant to do research on identification method of torque and speed. The identification method of motor output power is proposed through a series of experiment and theory analysis in this paper. The mainly research contens are presented as follows:1. Online identification of motor speed. For the purpose of identifying motor operating speed accurately, experiment scheme is designed to research on the relationship between measurable electrical parameters and motor speed. Frequency of rotor slot, which can reflect motor speed, is obtained through analyzing frequency spectrum of stator current. Then spectrum aliasing problem between slot harmonic and tooth harmonic is solved to achieve accurate identification of motor speed.2. Online identification of motor output torque. For the condition that torque-meter cannot be installed in actual, experiment scheme is designed to research on online identification of motor operating torque. The air gap torque is identified using measurable electrical parameters. And further the algorithm is improved and output torque is identified based on the relationship between air gap torque and output torque.3. Comparisons among methods of asynchronous motor energy assessment. Several popular online identification methods are analyzed. And the principle and error precision of each method are compared through experiment. The identification method is obtained to fit for engineering practice at last.