Vacuum circuit breaker
Vacuum circuit breaker EX-BB, is designed for switching the electric circuits at normal and emergency modes in industrial and power net units of three-phase alternating current with insulated or grounded via arc-suppressing reactor midpoint conductors with frequency of 50 and 60 Hertz, rated voltage up to 10 kV and for general purpose electric networks.
Vacuum circuit breakers are designed to be used in КРУ cabinets, including КРУВ installed indoor or outdoor, voltage class 6, 10 kV of three-phase alternating current for the systems with insulated midpoint conductor.
BB are used under normal climatic conditions (climatic design УЗ as per GOST 15150-69, groups M6, M7), as follows: upper operating effective ambient temperature is +40°C, taking into account temperature excess inside the КРУ; limiting low operating ambient temperature is -40°C; maximum height above sea level is 4500 m. When the cabinets are used at the height above 1000 m, requirements to the dielectric strength of insulation and nominal current should be reduced by the values in accordance with altitude correction as per GOST 1516.1-76 and GOST 151550-69. Relative air humidity (annual average) is 75% at 15°C; ambient dustiness is up to 10 mg/m; nonexplosive environment.
Vacuum circuit breaker is resistant to mechanical exposure factors as per GOST 17516.1-69 at vibration loads in the range from 1 up to 35 Hz for I degree of fixity, single impacts with acceleration up to 3g, duration from 2 up to 20 ms. BB provides normal operation and normalized parameters at heeling and trim difference in any position.
Vacuum circuit breaker of different designs can be manufactured, as well as supplied with adaptation kits manufactured on custom-order or from drawings provided by the customer. Moreover, it is possible to complete the circuit breaker with spring quick-detachable contacts of original design. Contact set parameters – prong diameter, rated current 1н, short-circuit current 1кз – are determined when ordered.
Arrangement and operation
Alternating current arc extinction is carried out in vacuum extinguishing chamber (VEC) by switch opening in high vacuum (residual pressure is about 10-6 mm mc). Metal vapor is current carrier when arcing. Due to the practical absence of environment in intercontact interval, metal vapor condensation at the moment of current passing through natural zero is carried out within extremely short time (10-5 s), after that electric strength of VEC is fast recovered. Vacuum electric strength is about 30 kV/mm that guarantees current interruption at contact divergence more than 1 mm.
Modern construction of VEC with axial-radial magnetic field is used in the circuit breaker. Placed in such a field, arc is always in diffusive state that decrease the wear which is not more than 1 mm after the switch resource is over.
Vacuum circuit breaker consists of three poles and a case where electromagnetic drives are placed. Electromagnetic drives can be manufactured with a magnetic catch or without it.
Major units of BB for current up to 1000 A are placed inside the closed insulation case made of strength and arc-resistant material; this protects pole elements from mechanical damage and electric arc impact of short circuit current.
Power and control units are manufactured of single-cased or double-cased design.