Investigations On Design Theory And Application Of Novel High Current Switches

With the increase of electrical energy consumption and high power energy usage, high current technology becomes one of the fast developing fields in the energy production, transmission, conversion, control, etc. Based on two projects of high current electrical switches, a design theory and its application about Vacuum Generator Circuit Breaker (VGCB) with two breaks in parallel and special switch in aluminum electrobath is proposed in this paper.According to the current transfer theory and phase control technique, a novel VGCB with two breaks in parallel is designed in this paper. Difference to the traditional design mode, it adopts a method of asynchronous opening two interrupters, which can select the interrupter with appropriate parameters to connect in parallel. Main Vacuum Interrupter (MVI) undertakes the rated current mainly, while Auxiliary Vacuum Interrupter (AVI) breaks the fault current. The current distribution in two interrupters can meet VGCB design requirement by suitable circuit structure arrangement. It stipulates a corresponding work flow in order to release the contact ablation, due to the difference of broken current characters. The current distribution under rated short-time tolerant current is tested, and so that the electrodynamic force of each part in VGCB is calculated. By synthetical analysis of the force effect and thermal effect, the VGCB can work steadily for a long-time in the closing state.From the current variety analysis of system source, generator source and the out of step fault current, together with the mathematic model of current transformation, transfer process equations of three fault current are deduced. The change trend of current transfer process and influencing factors are obtained due to the simulation results, and so, the coordination manners of MVI and AVI is ascertained. From the simulation of current transfer process, it is known that the current transfer of VGCB in rated short circuit breaking current can make true and current transfer process is related to fault current source style, initial current phase angle, system equipment parameters, contactor separation instant of MVI, and so on. It has exceeded the restriction of current transfer analysis in single current style and fixed contact separation instant at before.Based on the application research, a model of VGCB with two breaks in parallel is manufactured in this paper. By measuring the opening coil exciting time of Permanent Magnetic Actuator (PMA), a requirement of shortening the exciting time further is proposed. By current distribution test, it is proved that the circuit structure of VGCB can implement the current distribution reasonably. By the comparison of current transfer test and simulation analysis, the reason of current transfer and change trend are found. The VGCB model can satisfy the corresponding prescripts of National Standards of China. Some methods of heat dissipation improvement are also introduced.A set of specific high current switch is designed in this paper. It is made up of many small current switches in parallel by synchronous closing and opening technique, so it can switch on-off electrobath with non-powercut. The switching on-off flows are introduced in this paper. By calculating electrical parameters and simulating the switching motion process, the switch can achieve the current transfer of huge current. Through the dynamic and thermal stability analysis, the structure of many breaks in parallel can satisfy the stably running demand in closing state.