The 3-D Temperature Field Analysis Of Overload Relay

Overload relay is widely used in a variety of motor fault protection, which directly affects the running state of the motor. Overload relay operates based on the principle of current thermal effect, so the thermal analysis of the overload relay is important. The traditional engineering calculation method is difficult to acquire the information of the temperature field. By use of numerical analysis technology, the simulation of temperature field under different operating conditions is convenient to display operation characteristics of the overload relay. Therefore, the research on the 3-D temperature field analysis is important for the improvement of the performance and the design of overload relay.In this paper, by taking typical overload relay as object, the main research is as follows:1、According to the principle and the structure of overload relay, the equivalent heat path calculation method is discussed and the equivalent heat path model is established. And the finite element analysis method of the overload relay is analyzed to acquire the temperature distribution more accurately. In addition, the theoretical calculation methods of the curvature, the deflection and the thrust caused by thermal elastic deformation are studied on.2、 The finite element model of overload relay is established by ANSYS. The electricity-heat-structure coupling analysis method is used to study on the characteristics of temperature distribution, stress distribution and displacement change in different current situation. Design of the temperature acquisition circuit, real-time acquire of the temperature of thermal-bimetal system; The results of simulation, experiment and theory are compared to validate the correctness of the simulation method and the error reasons are found out to improve the performance and the design of overload relay.3、 The thermal simulation method of thermal-bimetal system with the shell is studied on. The temperature distribution is analyzed and the results between with and without the shell are compared. Because the space with the shell is limited and the air mobility and the heat dissipation is poor,the temperature of the system with the shell is higher than that without the shell.4、The research on the effects of ambient temperature and position arrangement on the temperature distribution of thermal-bimetal system is studied on. In the allowed arrange of ambient temperature, the effect of ambient temperature on the temperature distribution of thermal-bimetal system is less; what’s more, in the condition of limited design space(the angle between the copper and nickel chromium alloy and between the bimetallic strip is less than 30o), the temperature of thermal-bimetal system is raised with the increase of the angle.