Research On Optimization Of Maglev Chopper

Compared with traditional rail train, the maglev train has the advantages of less noise, strong climbing ability and small turning radius. For the city rail transit, the low-medium speed maglev train is a very competitive plan of public transportation. This paper study the suspended chopper which is the key device for controlling the suspended height of the maglev train.This paper cooperated with Tongji University "Chopper Optimization of Low-medium Speed Maglev Experimental Line" project, by utilizing new devices and new circuit structure, to optimize the existing chopper in weight, volume and efficiency.This article start with the analysis about main circuit structure of the existing Shanghai Lingang low-middle speed train maglev chopper, through the analysis of theory and simulation, found the existing problems. First, the bus capacitor can not be discharged, if the chopper power-fail suddenly and stop working, all energy in suspension electromagnet transferred to bus capacitor, as a result, capacitor voltage will be increased. So only to use high voltage bus capacitance with large capacity and utilize large power devices. Second, the charging contactor is the same type of main contactor, this increase the size and weight of the chopper, and also add the cost. Third, the chopper used the 1200V IGBT module as the switching device, with much loss, and with fan forced into cooling, which also lead to mass noise. Fourth, wires are used for electrical connection inside chopper, which is not convenient for production and maintenance.Considering problems in the existing chopper, redesign the chopper main circuit, then verified by simulation which in order to minimize the volume, weight and noise, improve efficiency and stability. The optimized of design mainly contain the following four points, first, use chopper switch circuit instead of charge contactor, which can control charge current at starting and provide input over current protection; second, add the bus discharge circuit, which can release the energy transferred from electromagnet to the filter capacitor when power off suddenly; third, using 650V MOSFET switch as the power switch device, replace the 1200V IGBT, this reduce switching loss; fourth, due to decrease of heat, cooling fan is canceled, this reduced the noise of the whole chopper.Based on the theory and simulation analysis above, to redesign the hardware of the chopper. The hardware circuit can be divided into main circuit and control circuit according to function, then introduce the hardware design respectively. After the optimization of the suspension chopper hardware circuit, the chopper turned into small and high-efficiency. For structure, the circuit is connected by pins directly, which simplified wiring and improve reliability.At last, the hardware is tested and results are analyzed. Compared with the existing chopper, the volume decreases 50%and the weight is reduced to 23%, with no fan and noise, which prove the chopper achieved the expected design goal after optimized.