Study On Thermoelectric Properties Of CuCr Contact In Motor Main Breaker

The main breaker of the motor train is an important component of the power supply system of the EMU.In case of failure,it may cause serious damage to the EMU’s high-voltage equipment and threaten the safety of passengers.As the core part of the main circuit breaker,the contact structure of the main circuit breaker directly affects the success or failure of the main circuit breaker.Therefore,the study of the structure performance of the main circuit breaker contacts has extremely importance.for improving the safety and reliability of the motor car.In this paper,hot isostatic pressing(HIP)is used to prepare dense and uniform CuCr contact materials at different sintering temperatures,and the thermoelectric properties of CuCr contacts are deeply and systematically studied.The specific research contents and conclusions of the artic are summarized as follows:(1)The HIP is used to prepare dense and uniform CuCr contact materials at different sintering temperatures.The key oxygen and nitrogen contents are better than the national standards.It is found that with the increase of HIP sintering temperature,Cr granules in CuCr alloy materials is also increasing.(2)The performance test analysis of the prepared CuCr contact shows that as the particle size of the second phase particles decreases,the density and hardness of the alloy will increase,and the conductivity will decrease.The electrical breakdown test of CuCr contacts was carried out and the microscopic morphology after electrical breakdown was analyzed.It was found that with the increase of Cr phase particle size,the electric breakdown ablation area increased,the breakdown ablation traces showed obvious outward extension trend,and the depth of the ablation pit was also deepen.(3)The function image of the breakdown field strength and the number of breakdowns is analyzed.It is concluded that reducing the particle size of Cr can significantly improve the vacuum electric breakdown characteristics of CuCr contact materials.The electric breakdown field strength will vary with the number of breakdowns.And sophisticated phenomenon will appear.Further research has drawn the mathematical expression of the relationship between the radius of CuCr and the breakdown field strength of CuCr alloy.(4)The thermophysical parameters of CuCr alloy and the heat transfer coefficient of the contact surface of the circuit breaker were calculated.The temperature field of CuCr electrical contact under high voltage arc was simulated by ANSYS software,and the relationship between the temperature distribution of the contacts and time is obtained.The overall temperature of the contact shows a trend of increasing first and then decreasing,and the temperature reaches a maximum value of 2626.17 °C after 10 ms of high voltage arcing.The above research results provide an experimental basis for the study of the heat resistance of the overall material of the contact.