Three-phase Asynchronous Motor Single Phase Operation Analysis

Three-phase induction motor with single-phase source is a special operating state of three-phase induction motor.The single-phase operating mode can directly use civil power supply,which not only enhances the flexibility and expand the operating range of the motor,but also avoid the low efficiency of the single-phase induction motor. Considering the specificity of the operating mode,it is significant to study operating characteristics of three-phase induction motor with single-phase source.Two theories- orthogonal magnetic field theory and revolving theory can be used to study three-phase induction motor with single-phase source.Revolving theory is classified as symmetrical component method,Morill revolving magnetic field analytical method and synthetic current analytical method.Compared with other methods,the synthetic current analytical method has such advantages as convenient computer aided computation,simple analysis and high precision.Thus the synthetic current analytical method is introduced to analyze the performance of the three-phase induction motor with single-phase source.According to he synthetic current analytical method,the three phase induction motor is treated as a single-winding motor.The elliptical rotating field inside the motor is treated as compounded by two circular rotating fields with opposite sequences,which are only induced by the current of reference winding.The other winding currents are considered as a component of the reference winding current after turn number and phase angle conversion.The expressions for positive sequence and inverted sequence currents are obtained by adding the component and the reference winding current together.On the basis of the expressions,and network graphic theory in modern circuit analysis,the loop matrix function,induced electrodynamic force functions,branch impedance voltage functions and branch voltage functions are deduced.The network functions are derived according to the KVL,which are used to analyze the performance of the motor.It is found that the operating performance of the motor is influenced significantly by external capacitance,terminal voltage and frequency.The effect of the variables on the motor is studied by finding out the dynamic rules and drawing corresponding relation graphs.The experimental results certify the validity of the proposed method.