In the optimum design of contactors, it is important to analyze the dynamic behaviors. In this paper, it proposes a new computational approach for analyzing dynamic characteristic of the energy-saving and bouncing-reducing double-coil contactor. According to the contactor's unique characteristic that it has two transferable coils, the paper builds two different sets of equations. One describes the period before the transfer position, and the other describes the period after the transfer position. The equations deal with the electrical circuit, electromagnetic field that can be calculated by using 3-D finite element method and mechanical system considering the influence of friction. The validity of the proposed method is confirmed by experiment. Finally, the paper gives an optimum design for the transfer position of the two coils. The result of the optimum design reduces both of the first and the second bounces of the movable contact.

In the optimum design of AC contactors, it is necessary to analyze the dynamic behavior. Moreover, movable contacts and core bounce have remarkable effect on the lifetime of contactors. A set of differential equations describes the coupling of the electric circuit, electromagnetic field and mechanical system taking account into bounce and the influence of friction. With virtual prototyping technology, the dynamic behavior, especially for contacts bounce, has been investigated according to different electrical circuit parameters. Two approaches are introduced to solve electromagnetic parameters. Based on 3D finite element static nonlinear analysis, the flux linkage and electromagnetic force can be evaluated with different air gap and exciting current for larger gap. In addition, concerning to the shading coil for smaller gap, magnetic circuit can facilitate the calculation. The validity of the proposed method is confirmed by experiments.

The gas-puffer effect has important effects on the interruption capability of a molded case circuit breaker (MCCB). In this paper, on the basis of a simplified model of an arc chamber with a single break, the effect of back-volume of an arc-quenching chamber on arc behavior in an MCCB is investigated. Firstly, using a 2-D optical-fiber arc-motion measurement system, experiments are performed to study the effect of back-volume on the arc-motion and gas pressure in an arc-quenching chamber. We demonstrate that the lower back-volume of the arc-quenching chamber is, the higher the pressure and the better the arc motion will be. Then, corresponding to the above experiments, the gas pressure inside the arc-quenching chamber is calculated using the integral conservation equation. The simulation results are consistent with the experimental results.

Short-time withstand current is one of the crucial nominal parameters in air circuit breaker. A numerical method to evaluate the short-time withstand current is proposed. Cylindrical current carrying bridge is introduced to describe the contact spot between movable and fixed contacts. Taking into account the action of ferromagnetic splitter plates, the variation of the conductor properties with temperature and the variation of contact spot radius with the electro-dynamic repulsion force, a transient finite element calculation model is developed by coupling the electromagnetic field and thermal field. The loaded short circuit current is considered as the short-time withstand current once the highest temperature is near to the melting point of the contact material. It demonstrates that the method is useful to evaluate the performance of the air circuit breaker.

A method is proposed to investigate the dynamic characteristics of a magnet release in molded case circuit breaker. With the static field assumption, two grids of the magnetic torque and flux linkage are calculated with the variation of the current and air gap, firstly. Considering the influence of tripping torque, coupled with circuit equation and mechanism motion equation, the dynamic characteristics may be obtained with Runge-Kutta 4 method. Experiments have been done to verify the method, and the difference between the calculated results and the experimental results is below 10%. In addition, the influence of the reaction spring on the protection characteristics is analyzed using this method. It demonstrates that the setting current varies with the initial angle and the stiffness of the reaction spring, and the variation with the initial angle of the reaction spring is closely linear but the stiffness nonlinear.

In the optimum design of AC contactors, it is important to analyze the dynamic behavior. Moreover, movable contact and core bounces have remarkable effect on the lifetime of contactors. According to a new kind of contactor with feedback controlled magnet system, this paper builds two different sets of periodically inter-transferred equations to obtain the dynamic characteristics of the contactor. The equations describe the coupling of the electric circuit, electromagnetic field and mechanical system taking account of the influence of friction. Then, the paper gives an optimum design to the dimension and the duty ratio of the contactor' pulse modulated wave (PWM) under different exciting, and proves, by experiment and simulation, that the bounce time of the contactor working in the optimized duty ratio is much less than that of the general AC contactors.