Design And Optimization Of Magnetoelectric Velocity Transducer In Vacuum Circuit Breakers

Vacuum circuit breaker is most widely used in the electric power system of transmission and distribution. During normal running, the vacuum circuit breaker is used to control devices and circuit connection or disconnection. Once the circuit or devices are breakdown, the vacuum circuit breaker is used to cut off them quickly in order to keep other circuit running normally. So vacuum circuit breaker has the function of control and protection in the power system of transmission and distribution. Its mechanical characteristic parameters will decide whether the power system runs normally or abnormally.The average speed of dynamic contact is selected as the testing signal, which plays an important role in the status parameters of vacuum circuit breaker. Then, designing a magnetoelectric velocity sensor with the modern sensor technology and finite element analysis theory to detect the average speed of dynamic contact. The thesis’ s main points are as follows:First of all, some advantages of the magnetoelectric speed sensor are introduced, such as without external power, small output impedance, without high gain amplifier, simple circuit, stable performance, etc. Choosing the longer-life magnet-moving velocity sensor. It is indicated that double-coil can improve sensor sensitivity though transforming the output induction electromotive force formula and analyzing the distribution of magnetic field.Using the finite element analysis software, the double-coil structure is compared with one-coil structure, the results show that the sensitivity of double-coil sensor is higher. So the structure of sensor is ensured.Then, a preliminary size of the permanent magnet, coil and coil skeleton are designed though analyzing and calculating the sensor installation space in the vacuum circuit breaker.Based on the sensor output characteristic equation, it is indicated that the structure of double-coil and series opposing can improve the linearity of sensor. Calculating the change of the magnetic flux by the field calculator and importing these data to data-processing software to analyze visually the linearity and sensitivity of sensor. The results show that the structure of double-coil and series opposing improve the linearity of sensor more than series, though sensitivity of sensor is smaller slightly. So the connection mode of coil is sure. In addition, the principle of velocity measurement is sure by sensitivity formula.Finally, the influence of the changes are analyzed in the coil axial layers, coil radialnumber of turns and the distance between the two coils on the performance of the sensor,conducts the optimization analysis on sensor coil and the distance between the two coil using the parameterized analysis method in the finite element analysis software, determines the final optimal size and completes the magnetoelectric sensor optimization procedure.Then the rationality and reliability performance of the optimized structure of magnetic sensors is proved through experiments. The results of experiment indicate that the sensor designed in this paper can performs very well, and meets the requirements of actual detection.