Performance And Working Principle Of High Voltage Vacuum Circuit Breakers
High Voltage Vacuum Circuit Breaker Performance Introduction
High-voltage vacuum circuit breakers can be frequently operated or repeatedly interrupt short-circuit currents within their operating current range; their mechanical life can reach up to 30,000 cycles, and the number of full-capacity short-circuit current interruptions can reach 50.
High-voltage vacuum circuit breakers are suitable for reclosing operations and have extremely high operational reliability and service life.
High-voltage vacuum circuit breakers (standard type) employ a vertical insulating cylinder to protect against the effects of various climates; and in terms of maintenance, usually only occasional cleaning or lubrication of the operating mechanism is required.
High-voltage vacuum circuit breakers (pole type) adopt a solid insulation structure—integrated solid-sealed poles—achieving maintenance-free operation.
High-voltage vacuum circuit breakers can be installed in switchgear in fixed, withdrawable, or frame-mounted configurations.
Introduction to the Working Principle of High-Voltage Vacuum Circuit Breakers
Permanent Magnet Operating Mechanism Principle: When the circuit breaker is in the closed or open position, no current flows through the coil. The permanent magnet uses the low magnetic impedance path provided by the moving and stationary iron cores to hold the iron core at its upper and lower limits without any mechanical latching. When an action signal is received, the current in the closing or opening coil generates a magnetomotive force. The magnetic fields generated by the coils in the moving and stationary iron cores are superimposed with the magnetic field generated by the permanent magnet. Under the action of the combined magnetic field force, the moving iron core, along with the drive rod fixed on it, drives the switch body to complete the opening and closing task at a specified speed within a specified time. This mechanism is called a two-position bistable principle structure because the moving iron core can be held at either end of its stroke without consuming any energy. In contrast, in traditional electromagnetic mechanisms, the moving iron core is held at one end of its stroke by a spring, while the other end is protected by mechanical latching or electromagnetic energy. As described above, the permanent magnet operating mechanism achieves all the functions of a traditional circuit breaker operating mechanism through a special combination of an electromagnet and a permanent magnet: the permanent magnet replaces the traditional release mechanism to maintain the limit position, and the opening and closing coils provide the energy required for operation. It can be seen that due to the change in working principle, the total number of parts in the entire mechanism is significantly reduced, potentially leading to a substantial improvement in overall reliability. Due to the inherent characteristics of the permanent magnet mechanism, the reliability of the circuit breaker can be improved. Furthermore, since the opening and closing characteristics are only related to the coil parameters, the opening and closing characteristics of the permanent magnet mechanism can be controlled by an electronic or microcomputer system, achieving intelligent control of speed characteristics and possessing self-detection capabilities. The control circuit can employ electronic control and an external DC contactor for closing.
Arc-extinguishing principle of the arc-extinguishing chamber: The high-voltage vacuum circuit breaker (equipped with a permanent magnet operating mechanism) adopts a vacuum arc-extinguishing chamber, using vacuum as the arc-extinguishing and insulating medium. The arc-extinguishing chamber has an extremely high vacuum degree. When the moving and stationary contacts are energized and opened under the action of the operating mechanism, a vacuum arc will be generated between the contacts. At the same time, due to the special structure of the contacts, an appropriate longitudinal magnetic field will also be generated in the contact gap, causing the vacuum arc to remain diffuse and to burn evenly on the contact surface, maintaining a low arc voltage. When the current naturally crosses zero, the residual ions, electrons and metal vapors can recombine or accumulate on the contact surface and shield within microseconds. The dielectric insulation strength of the arc-extinguishing chamber break is quickly restored, thereby extinguishing the arc and achieving the purpose of breaking. Because this high-voltage vacuum circuit breaker uses a magnetic field to control the vacuum arc, it has a strong and stable breaking current capability.
