Developmental Research on The Current-Type SCR Bridge Phase Modifier with Forced Commutation Using a Pulse Transformer

When the bridge rectifier constituted with self quenching devices.Derives a leading current from the supply system，there is a question how to treat the conservative energy in the AC side inductance at the instant of commutation。Generally，that energy is absorbed into the sunbber circuit and consumed as loss.But，if the SCR bridge with the forced commutation ability is used，that energy can be treated effectively because of the overlap phenomenon.In order to generate the forced commutation pulse voltage，a single phase bridge constituted with the self quenching devices is used，and the generated pulse voltage is applied to the current-type thyristor bridge via a pulse-transformer。By a method of using the neutral point of the input-transformer，more advantage is brought at the point of view of the needed commutation voltage amplitude，the withstand voltage of device，allowable current of the bridge，and the inductance of the AC side，therfore that bridge will be able to apply easily to the high power system Using this current-type bridge，the thyristor phase modifier is constituted。As the reduction strategy of the higher harmonics，the phase-shifted multiplex method is employed。Availability of the method in which the phase shifted by 20°and the triple multiplex，is cirtified.If some ripple in the DC current is admitted，it is possible to select more small inductance of the DC reactor that is an energy storage element.The ratio of the phase modifier capacity(Kvar)to the inherent capacity(Kvar)of such reactor is increased when that DC reactor is used in the phase modifier apparatus。For the smooth movement form“C”action to“L”action and vice versa，every control signal is provided in parallel，and the either of the two is selected by the exchange instructions.Hereafter，the application and improvement of this apparatus will be investigated。

When the bridge rectifier constituted with self quenching devices. derives a leading current from the supply system, there is a question how to treat the conservative energy in the AC side inductance at the instant of commutation. Generally, that energy is absorbed into the sunbber circuit and consumed as loss. But, if the SCR bridge with the forced commutation ability is used, that energy can be treated effectively because of the overlap phenomenon.In order to generate the forced commutation pulse voltage, a single phase bridge constituted with the self quenching devices is used, and the generated pulse voltage is applied to the current-type thyristor bridge via a pulse-transformer. By a method of using the neutral point of the input-transformer, more advantage is brought at the point of view of the needed commutation voltage amplitude, the withstand voltage of device, allowable current of the bridge, and the inductance of the AC side, therfore that bridge will be able to apply easily to the high power system.Using this current-type bridge, the thyristor phase modifier is constituted. As the reduction strategy of the higher harmonics, the phase-shifted multiplex method is employed. Availability of the method in which the phase shifted by 20゜and the triple multiplex, is cirtified. If some ripple in the DC current is admitted, it is possible to select more small inductance of the DC reactor that is an energy storage element. The ratio of the phase modifier capacity (Kvar) to the inherent capacity (Kvar) of such reactor is increased when that DC reactor is used in the phase modifier apparatus. For the smooth movement form "C" action to "L" action and vice versa, every control signal is provided in parallel, and the either of the two is selected by the exchange instructions.Hereafter, the application and improvement of this apparatus will be investigated.