| With the development of power electronics technology,inverter-fed motor is used more and more widely,but the harmonic voltage injected into the motor by the frequency converter causes the motor efficiency to decline,in view of this problem,In this thesis,time and space harmonics in variable frequency motor are systematically studied.On this basis,the rotor slot of induction motor is optimized by finite element method.Finally,a rotor slot of induction motor suitable for variable frequency power supply is obtained.The main contents are as follows:1.In order to study all kinds of harmonics in variable frequency motor,the space and time harmonics in motor are discussed in detail from the angle of theoretical analysis.In the process of analysis,simple and complicated research methods are adopted,such as from single coil to multiple coils,from single phase to three phase,from space harmonics to time harmonics,from centralized windings to distributed windings.Finally,the distribution law of various harmonics in the motor is obtained,which lays a theoretical foundation for the follow-up study.2.By studying the design characteristics of rotor slot under sinusoidal power supply and combining with the particularity of induction motor supplied by frequency conversion,the differences of motor design concepts under sinusoidal and frequency conversion power supply are compared and analyzed,and the basic rules of rotor slot design under frequency conversion power supply are summarized.3.The resistance increment coefficient and reactance reduction coefficient of the rotor guide are introduced as the criteria to measure the merits of different slots.The finite element eddy current field is used to analyze the electromagnetic field distribution of different slot structures,and the structure is optimized step by step.The transient field of finite element is used to further analyze the loss and harmonic characteristics,which verifies that the slot of convex arc blade rotor proposed in this paper has good effect in suppressing harmonics and reducing losses. |
