Analysis Of Harmonic And Radial Forces Of Multi-Speed Single-Phase Induction Motors With Capacitor Operation

At present,energy resources are in short supply and the ecological environment is deteriorating.Therefore,it is necessary to improve the efficiency of the motor and cope with outstanding energy problems through energy saving and emission reduction.Single-phase induction motors are widely used in industry and daily life,and their output is huge.It is of important research significance that how to improve their efficiency.The existence of harmonics in the induction motor can cause unsatisfactory results,such as spikes and recesses of the speed-torque curves.Meanwhile,the harmonics can result in stray load losses and low efficiency.At the same time,the presence of harmonic torque produces vibration and noise,which affects the performance of the motor,especially the starting torque and the maximum torque.In this paper,the analysis of the spatial harmonics of single-phase induction motors establishes a theoretical basis for suppressing harmonics of motors and improving efficiency of motors.First,a brief introduction of the type of single-phase motors is presented.Also,the characteristics of various types of motors are analyzed.The harmonic research status of single-phase motors at home and abroad is introduced,and the analysis methods of single-phase motors are studied.Secondly,the working principle and speed regulation theory of single-phase motor is analyzed.Due to the asymmetry of the structure of the winding and the characteristics of the single-phase power supply,the single-phase motor has an elliptical magnetic field waveform in the air gap.The distribution of the air gap magnetic field are analyzed,and the reason for the formation of the elliptical magnetic field is explained.The electrical equations of the motor under different speed conditions are derived,which can be used to calculate the performance parameters of the motor.Then,the equivalent circuit including the harmonics is derived through analyzing the harmonic magnetic field in the air gap of the motor.The Fourier series is used to express the spatial harmonics in the motor.According to the magnetomotive force expression generated by the winding,the expression of magnetic flux in the air gap is obtained,and the electromotive force induced by the air gap magnetic field in the winding is further obtained.Based on the theory of double rotating magnetic field,the harmonic equivalent circuit of the motor is obtained from the expression of electromotive force.The equivalent circuit is used to analyze the running performance of the motor,including the electromagnetic torque of the motor.The harmonic components in the electromagnetic torque are analyzed to determine their frequency and amplitude.Finally,the simulation model is established,and the simulation results are obtained,using which to verify the theoretical analysis.The output torque curve of the motor is analyzed to obtain the magnitude of the torque pulse,and the harmonic component that causes the pulse is determined.An experimental prototype was built and a prototype experiment was carried out to obtain the operating characteristics of the motor,which further verified the correctness of the theoretical analysis.