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.
|Input voltage frequency, Hz||50|
|Rated voltage, kV||6|
|Maximum operating voltage, kV||7,2|
|Test voltage, kV|
— one-minute, 50 Hz
— full lightning impulse
|Rated amperage, A||1000|
|Rated voltage of auxiliary contacts, V|
|Rated AC amperage of auxiliary contacts, A||5|
— arc chute breaking rated current, kA
— normalized percentage of DC component of the breaking current, %
|Average lifetime, years||30|
Vacuum circuit breaker EX-ВВ 6-20/1000 UZ-3 type, further on ВВ, 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 Hz, rated voltage up to 6 kV and for general purpose electric networks.
Vacuum circuit breakers are designed to be used in KRU cabinets, including KRUV installed indoor or outdoor, voltage class 6, 10 kV of three-phase alternating current for the systems with insulated midpoint conductor.