Research On Key Problems Of Self-excited Retarder

Self-excited retarder is a new type of retarder which integrates braking and power generation performance.It can not only decelerate the vehicle,but also use the kinetic energy of the vehicle to generate electricity.It has the advantages of safety,energy saving and environmental protection,and has great research value.At present,the basic research on electromagnetic field and temperature field characteristics,calculation of braking moment,mathematical model of temperature change and control of heat recession resistance in the field of self-excited retarder in China are relatively backward.In this paper,a self-excited retarder is taken as the research object,and the ultimate goal is to improve the braking performance.Several key problems of self-excited retarder are studied.There is a coupling relationship between electromagnetic field and temperature field of self-excited retarder.In order to explore the characteristics of electromagnetic field and temperature field of self-excited retarder,this paper simulates the electromagnetic field and temperature field of self-excited retarder based on ANSYS software.Firstly,the three-dimensional finite element model of the self-excited retarder is established,and the electromagnetic field simulation calculation of the self-excited retarder prototype is carried out.The magnetic flux density,eddy current density,eddy current loss and other electromagnetic field characteristics of the self-excited retarder are solved.Then,the eddy current loss obtained from electromagnetic field simulation is taken as the internal heat source,and the temperature change cloud of self-excited retarder is obtained by coupling calculation.In order to improve the accuracy of simulation,the electromagnetic field parameters of self-excited retarder will change with temperature.By modifying the electromagnetic field parameters varying with temperature,the bidirectional Electromagnetic-Thermal coupling simulation calculation is carried out with the method of bidirectional cyclic iteration,and the characteristics of the electromagnetic field and temperature field are obtained after the parameters are stabilized.The mathematical models of braking moment and braking power of self-excited retarder are deduced by force analysis method and numerical analysis method.According to the strong skin effect of eddy current in Electromagnetic-Thermal coupling simulation,a virtualboundary method for calculating the temperature of external rotor is proposed.The temperature field mathematical model of the external rotor is deduced by using heat transfer theory and virtual boundary method,which provides theoretical basis for the design and performance analysis of self-excited retarder.Finally,a test bench for performance test of self-excited retarder is built.Speed and torque tests and traction tests are carried out on the self-excited retarder prototype.The output conditions of the self-excited retarder prototype are obtained,and the accuracy of the mathematical model of braking torque and temperature field is verified.Aiming at the thermal decay of self-excited retarder prototype in the results of bench test and virtual coupling simulation,a fuzzy control scheme for optimizing the temperature of external rotor is proposed.The output mode of the self-excited retarder prototype is adjusted by setting the safety threshold temperature,taking the temperature difference and the change rate of the external rotor as input variables,and taking the change of the conductive angle of the thyristor as output variable.After that,the optimized self-excited retarder prototype is trailed again.By comparing the two bench test results before and after the optimization,the stability of the output performance of the self-excited retarder prototype can be effectively improved.