| The slot combination and skew slot are important factors that influence induction motor performance,loss,vibration,and noise.But the selection of them is mostly based on prior design experience in the design of induction motors,and existing research has not been able to fully explain the mechanism and law of the influence of slot combination and skew slot on induction motors.On the other hand,when it comes to the rotor skew slot and inverter power supply,the use of the finite element method would take a long time to compute.To address the aforementioned issues,this dissertation developed an electromagnetic analytical model for cage rotor induction motors that can take into account the interaction of harmonics in the induction motor under slot combinations,skew slot,and the inverter power supply.Firstly,the interaction between various harmonics in the motor is theoretically derived,and the modeling process of the electromagnetic analytical model is given in detail.The model equates the cage rotor winding to a multi-phase winding using the rotor multi-loop method.The air-gap function is then calculated using the conformal mapping to account for the slot effect.The inductance is calculated using the winding function to account for the high-order harmonics in the air-gap magnetic field.The skew slot is considered using axial sectioning.The state equation is established according to the equations of voltage and motion,and an iterative approach is used to solve for the electromagnetic characteristics of the induction motor.Secondly,a 7.5 k W three-phase,four-pole induction motor is used as a research object.The stator and rotor currents,electromagnetic torque,and air-gap flux density of the prototype are calculated at no load and at rated load.The comparison with finite element results demonstrates that the model can accurately consider the interactions between various harmonics within the motor.Furthermore,the method of accounting for saturation effects is discussed and its validity is analyzed.The saturation effect and skew slot on the harmonic characteristics of the motor are analyzed.Finally,the stator and rotor currents,electromagnetic torque,and air-gap flux density are computed by the electromagnetic analytical model under various rotor slot number,skew slot angles,and inverter power supply conditions,and the impact of various rotor slot number,skew slot angles,and inverter power supplies on the harmonic characteristics of an induction motor is obtained.Meanwhile,the finite element method is used to verify. |
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