Research On Field Test Method Of Motor Efficiency Based On Electromagnetic Force Mechanism

With the acceleration of industrialization in China,the problem of energy waste is getting worse.Among them,small and medium-sized three-phase AC induction motors are the most widely used high energy-consuming electromechanical products.Due to the long service life and rough manufacturing process,this kind of motor running efficiency is generally low,so the study of motor evaluation technology is particularly important.Now the motor efficiency assessment is mainly dependent on laboratory testing,which is complex and costly and can’t be applied to all motors.Aiming at the shortcomings of the current detection method,this paper presents a field-based portable motor energy efficiency detection method.This method is based on the theory of electromagnetic force and electromagnetic induction principle and takes use of the impact on the voltage and current.It takes use of sensorless Speed and torque on-line identification technology to calculate the output power of the motor,mainly including the following aspects.First,this paper briefly introduces the structure and working principle of three phase ac asynchronous motor.The mechanism of the rotor frequency component in the stator current under the action of the electromagnetic induction is described in detail,and the electromagnetic mechanism is explained from the microcosmic mechanism force and air-gap torque generation,through the machine side electrical quantity derived air-gap torque calculation formula,thus confirming the theoretical basis of this article.Secondly,this paper presents a sensorless based rotational speed and torque online identification algorithm,using two kinds of rotor frequency calculation method.By using the fast fourier transform(FFT)to obtain the spectrum,the rotor frequency is extracted,so as to get the motor speed.In order to improve the identification accuracy of the rotor frequency,respectively,using Zoom FFT spectrum refinement technology and the spectrum correction technology based on the ratio method to optimize the stator current spectrum to improve the spectral resolution.In addition,considering the importance of the stator flux in the calculation of the air-gap torque,two stator flux linkage calculation methods are proposed: the new pure integral method and the stator flux observer based on the low pass filter.The new pure integral method uses high precision complex Simpson integral model and solves the integral initial values and zero drift compared with the traditional trapezoidal method,so significantly improved the stator flux linkage identification precision.Although the pure integral method can overcome the initial values,sometimes still can’t meet the accuracy requirements.The low flux filter based stator flux observer model does not exist integral initial and zero drift,so the highest accuracy.The stator flux observer model based on low flux filter doesn’t exist integral initial values and zero drift,so as to identify the highest accuracy.Finally,the system simulation platform is built by Matlab/Simulink and the various aspects of the calculation program were integrated into the module can be directly called which are aimed to verify the validity of the sensorless speed and torque on-line identification technology.Through the simulation and comparison of the two stator flux linkage algorithms,this paper selects the stator flux observer based on the low-pass filter and the motor speed identification algorithm based on the stator current leveling method.Finally,the algorithm is verified by the experimental platform,and the simulation results and experimental results are given to verify the accuracy of the proposed algorithm.