General :
The ultimate quality of electrical power supply is mainly determined by the medium voltage system. One of the most significant parts of this system is constituted by the switchgear circuit breakers.Over breakers employing other arc-quenching principals, vacuum circuit breakers offer several advantages particularly being practically maintenance free and capable of performing switchgear operations even in critical circumstances.The vacuum circuit breakers are perfectly conducting at the opening up to the precise moment of the alternating current zero point and completely insulating instantly after that point, hence vacuum breakers can be assumed to be "the ideal arc interrupting" circuit breakers. The vacuum arc of short lenght and forms of a plasma of high conducting metal vapours sustain a very low arc voltage until extinguishing take place at natural current zero point. Furthermore, the vacuum comprises physically the ideal insulator due to the theoretically impossible start of ionization process which causes the instant condensation of essential metal vapours on shield and contacts. The energy level developed inside the arc-quenching chamber is minimum because of the very low arc voltage related to immediate recovery of dielectric strength. Additionally, the energy necessary to the operating mechanism can itself be very reduced due to low strokes and minimized moving masses. Consequently, with the combination of these advantageous energetic features, from both arc-quenching media and operating mechanism, which provide practically free maintenance and capability of performing wide range of switching operations, the PVB type vacuum circuit breakers are ideal choice for your medium voltage system.
Description :
PVB type vacuum circuit breaker is mainly composed of:
VACUUM INTERRUPTER
Vacuum interrupters are the most critical parts of vacuum circuit breakers since the current is interrupted inside. A standart vacumm interrupter is formed by a cylindrical vacuum containment chamber with insulating envelope sealed between two metal parts. Due to the extremely low pressure of 10³ to 107 torr inside this chamber,only a relatively small contact gap is required to achieve a high dielectric strength.Since the breaking capacity of a vacuum interrupter depends largely on the behaviour of the arc produced between contacts, axial magnetic field concept has been applied to the vacuum interrupters used in PVB type vacuum circuit breakers to increase the breaking capacity.In this method, two main butt contacts have an axial arrangement inside the vacuum chamber; one of them is fixed and the other is an axial motion contact. When the latter moves, tightness is ensured by means of metal bellows, the ends of which are welded to the rod of this moving contact on one hand and to the bottom part of vacuum chamber on the other hand. Material and design of these contacts have been selected with the aim of ensuring the best interrupting performances within the widest conditions of use. A cylindrical shield is provided inside the vacuum chamber on which the contact metal molecules are vaporized by the condensation to prevent the reduction of its insulation ability.Briefly, the design and production of vacuum interrupters ensure permanent maintaining of vacuum quality.
SUPPORTING FRAME:
This master part of the PVB type vacuum circuit breaker is a multifunctional part intended for fixing the vacuum interrupters, the operating mechanism and their connections. It ensures both phase-to-phase and phase-to-earth insulation, the earth being formed by the metal part of the breaker. Its lower part including the bearings for operating shafts of vacuum interrupters connects the operating mechanism to the live part of the circuit breaker. This frame is made of composite material ensuring very high mechanical and dielectric reliability.
OPERATING MECHANISM
All PVB type vacuum circuit breakers are equipped with PCRR 1000 type operating mechanisms processed by using spring stored energy independent from the direct operators access and also by enabling auto-reclosing. This operating mechanism is remote electrical control type and a manual safety operation can be carried out by means of a handle.Moreover, PCRR-1000 type operating mechanism include the pressure springs for contacts which are kept away from live parts and easily accesible for measurement of contact stroke or erosion. The special design of this operating mechanism has been aimed at complying with the particular performances of the PVB type vacuum circuit breakers,especially with regard to reliability and mechanical life.
DIMENSIONS
PRODUCTION RANGE
