The FZN25-12D type vacuum load break switch and FZRN25-12D type combination appliance adopt a overall structure where the operating mechanism is arranged on the side of the main circuit (available in right or left side arrangement according to user's needs). The main conducting part consists of insulation cover, static contact, movable contact, conductive cylinder, and vacuum arc chamber. The combination appliance also includes a current-limiting fuse.
This product uses the TF351 type vacuum arc-extinguishing chamber with a ceramic outer casing and 25 copper contacts. It features a flat contact structure, which results in minimal electrical wear and a long service life. With high breaking and closing capabilities, it offers strong performance and easy operation and maintenance. The fused switch is integrated with the operating mechanism, combining the functions of an isolating switch, load switch, and grounding switch into one compact structure. It has a small size, convenient installation, and flexible operation.
The switch is equipped with a dynamic isolated contact and a vacuum arc-extinguishing chamber, which are arranged in series and linked according to the specified operating procedure, achieving a one-time operation. The cone-shaped static contact, insulation cover, and movable contact structure separate the busbar and load switch units, ensuring the personal safety of workers. When the grounding switch is closed, the movable contact automatically isolates the breaking point, providing excellent protection. The switch, grounding switch, movable contact, and cabinet door light are strictly in accordance with the "five preventions" mechanical interlocking to prevent misoperation.
The switch mechanism is a spring-stored energy type, featuring both manual and electric energy storage functions. Once energy storage is complete (with the spring at the midpoint), it will automatically close, and for opening, it can be done manually with a decoupling lever or by an electromagnetic coil. This facilitates the implementation of remote control requirements for switch opening and closing operations.
The switch can be powered by both AC and DC sources, and its working principle is similar to that of a circuit breaker. It is generally equipped with a simple arc extinguishing device, but its structure is relatively simple. The diagram shows a type of compressed air high-voltage load break switch. During breaking, under the action of the opening spring, the main shaft rotates clockwise. On one hand, the piston moves upward by compressing the gas through the crank-slider mechanism; on the other hand, the transmission system composed of two sets of four-link mechanisms opens the main contact first, and then the arc extinguishing contacts, blowing out the arc with the compressed air from the nozzle. When closing, the main contact and arc extinguishing contacts rotate clockwise at the same time under the action of the main shaft and the transmission system, with the arc contacts closing first and then the main contacts closing subsequently. During closing, the opening spring is also storing energy. As the load break switch cannot interrupt short-circuit currents, it is often used in combination with a current-limiting high-voltage fuse to not only complete the function of breaking the circuit but also reduce the thermal and mechanical forces caused by short-circuit currents.