Theoretical Research And Design Of High Voltage Permanent Magnetic Actuators

The permanent magnetic actuator (PMA) is characteristic of few parts, free maintenance, high reliability and adaptability to the vacuum circuit breaker (VCB). It has been used extensively in the middle-low-voltage switches from 10 to 35 kV but had a small share of market compared with that of the spring actuator, and done nothing especially for the high-voltage switches for years. The high-voltage PMA must be driven by a larger startup current resulting in unwanted temperature and hard control, so it is costly and impracticable. On the other hand, to study and develop the PMA researchers depend on too much experience instead of a comprehensive theoretic system.Aiming at the above awkward situation, the dissertation dives into the theory, design, simulation and experiment of the new PMA. The characteristics of actuators are studied based on the mechanical and electromagnetic theories. They are then designed, analyzed and modified though the computer-aided technologies and virtual simulation technology. An advanced test and control system of HV switches is used to verify the motion and electrical characteristics of the single-stable prototype. The dissertation covers the following contents.Firstly, a broad overview of the past and present of PMA at home and abroad is given in the aspects of mechanical structures, permanent magnet materials and placement, windings arrangement, power and control, mathematical physics, CAT and test technologies. The long-trip, high-voltage and low-current PMA is of huge social and economical values from its today and future.Secondly, as a result of study on the electromagnetism of PMA, mathematical models of three kinds of PMA are established, followed by how to solve them, especially the fractal finite element method.Thirdly, an equivalent magnetic circuit is set up for the bi-stable PMA. Then a new method on the basis of spatial flux tubes is proposed to solve the emanative permeance. The magnetic circuit's influence on the retention is also analyzed. Two coupled magnetic short-circuit rings are fixed in the opening gap, which are expressed by mathematic models and simulated to prove a lower opening current and a higher opening speed. The design is aiming at the high-voltage and long-trip PMA. Finally, the initiative design of new single-stable PMA is to solve the closing problem of high-voltage and long-trip one. For the purpose, three chapters from five to seven in the dissertation focus on analysis of the magnetic circuit, design and simulation of the structure and motion as well as the test of the physical prototype, a gap-variable and self-locked single-stable PMA. The results prove that the design is practicable and effective, and improves largely the starting ability when closing. However, it is pointed out that the new PMA is creative but later modification is necessary for field use, not only itself but also the test and control system.