The Research On Permanent Magnetic Actuator Characteristics Considering Eddy Current And Temperature Effect

With short working hours and high action speed, the activity of dynamic iron core and the instantaneous swicth of coil current would generate eddy current in the dynamic and static iron core when the permanent magnetic actuator of vacuum circuit breaker was working. The eddy current would weaken the magnetic field of the permanent magnet, which had a great impact on the characteristics of the actuator. Environmental temperature variations can change the property of the permanent magnet,resistance and capacitance. It also had a great impact on the characteristics of the actuator. The coil temperature rise is also an important factor that cannot be ignored to the reliability of the actuator. It can also improve the dynamic characteristics of the actuator by adjusting the vaule of resistance, capacitance and coil inductance. The study of permanent magnetic actuator’s characteristics taking the influence of eddy current and temperature into account has important significance.This thesis focuses on the study of12kV vacuum circuit breaker with permanent magnetic actuator. And it is based on the finite element method, electromagnetic field theory and temperature field theory.Then the results of actuator’s characteristics taking the influence of eddy current and temperature into account is obtained through theoretical analysis and numerical simulation, and imprvement measures are put forward. The major works are presented as follows:Fist of all, the mathematical model of the dynamic characteristics of the actuator was deduced considering the impact of eddy current.The influence of eddy current on the characteristics of square and circular permanent magnetic actuator was analyzed and studied. The changes of electromagnetic force, speed, action time and other parameters of permanent magnetic actuator with different materials and structures was contrast analyzed.Then its loss was calculated and analyzed. Secondly, the influence of temperature on the property of the permanent magnet, coil resistance and capacitance and other parameters were studied.The characteristics of permanent magnetic actuator was analyzed and studied at different temperatures. The influence of different vaule of resistance capacitance and coil inductance on the characteristics of permanent magnetic actuator was analyzed and studied.The coil temperature rise caused by power loss was calculated, and the measure for preventing coil’s over-heating was put forward. The calculation results show that the action time of the permanent magnetic actuator will increase for the effect of eddy current. In the action process of the actuator, the eddy current loss is great. Low conductivity and high permeability material should be used in the design of permanent magnetic actuator, the structure of dynamic and static iron core also can be specially designed. While the temperature increasing, the action time of the permanent magnetic actuator will increase. By adjusting the excitation circuit parameters, the permanent magnetic actuator can quickly action. In the working process of the actuator, the coil should be avoided long-time working and large exciting current.