The Electromagnetism And Temperature Coupling Calculation And Analysis Of Induction Motor With Compound Cage Rotor

Due to its many advantages,such as good operation performance,squirrel-cage induction motor is widely used in the industrial field.However,its start-up performance is usually poor because of structural characteristics.In order to match the start-up requirements,the capacity is often several times to the load power,,which made it limited that the application of the induction motor in heavy load or large load fluctuation,in turn causes energy and material waste.The induction motor with compound cage rotor(IMCCR)researched in this paper utilizes the electromagnetic characteristics of different bars to enable the motor to have both high start-up performance similar to a solid rotor motor and good operation performance like a squirrel-cage motor,which opens up a new direction for the research of composited rotor.First of all,according to the theory of electromagnetic field,using time-stepping finite element method coupled electromagnetic fields and circuit calculates the transient electromagnetic performance of a IMCCR prototype in a power level of3 k W.The start-up condition is taken place by locked rotor condition simulation,and it is verified by experiments.the effects of different alloy ratios on the start-up performance are studied.A comparative analysis to the effects of different alloy ratios on the distribution of flux density and current density on rotor is made,and the optimum ratio is obtained.Taking account of all the alloy bars,the variation of the magnetic permeability of the alloy under different operation conditions is investigated by simulation.The continuous curves of the current and speed under the conditions of no-load,half-load and rated load of the IMCCR prototype and common cage induction motor(CCIM)are respectively graghed.According to the trend of the curve,the factors affecting the start-up time of the IMCCR are analyzed.Accordingto the working characteristics of the crane motor,the changes of the efficiency and power factor of the IMCCR and CCIM under low power load are studied,and the performance advantages of IMCCR in low load power are analyzed.For the case of poor power supply stability,the impact of the switching power supply system on the operation of IMCCR is systematically analyzed.The results show that the switching power supply has less influence on the speed and current of the IMCCR.Secondly,on the basis of the traditional double-cage slot,three new slots with different alloy arrangement patterns are proposed.The start-up performance and operation performance of those new slots are compared and analyzed,and it is found that the rotor slot with 80% copper alloy bar in lower cage can substantially improve the start-up performance under the premise of maintaining the same of operation performance as the prototype slot.Based on this slot model,the multivariable optimization design of start-up performance is studied.The conclusion that the alloy resistivity has almost no effect on the start-up performance is obtained,which provides a basis for optimizing the operating efficiency of the motor.Finally,taking the calculation results of the loss in the electromagnetic field calculation as the heat source for the transient temperature field calculation,the transient temperature field in the whole domain is calculated for the prototype model of IMCCR,which provides the basis for monitoring of intelligent motors.For the key problem of high temperature rise of the motor,the influence of dissipating heat structure on the casing and rotor structure on the temperature distribution inside the motor is investigated.The results show that the temperature rise of the motor can be reduced to some degree by changing the structure of the casing heat-dissipation fins and rotor.