Gimba Mafi Yawanci (Wakar Iyali da Kafin Yawanci)

Tana da gaba na circuit breaker na elektrikin da shi ya kai shine bayar da fadada masu karamin. Idan ba a taka da abubuwan da ke daidai, amma yana da kyau a lura cewa, circuit breaker wanda yake da shi ya fi zama daidai a matsayin na yakin. Duk da haka, ana bukatar shi ne don bayar da fadada masu karamin.

Saboda haka, yakin da take da circuit breaker ya kamata ta da inganci kadan da baya. Don in samun wannan inganci, an yi tsarin da ya zama mai zurfi da duk da yadda ake fuskantar da ita.

Fadada da take da masu karamin a lokacin da ake fadatar da su da karamin da suka yi a lokacin da ake fadatar da su, suna da muhimmanci a lokacin da ake gudanar da circuit breaker.

Fadada da take da masu karamin, yanayin da masu karamin suka yi, da kuma karamin da suka yi, suka dogara da abubuwa da ke daidai, da karamin da voltage rating na circuit breaker.
Kurba na yakin da take da circuit breaker ya kasance a kan takardun da aka bayar da ita a kan gabashin.
A nan a kan kurba, X axis ya nuna lokaci a milli seconds da y axis ya nuna yanayin a milli meter.

Idan a lokacin da T0 karamin ya faru a kan closing coil. Ba lokacin da T1 masu karamin ya faru zuwa fixed contact. Ba lokacin da T2 moving contact ya kasa fixed contact. Ba lokacin da T3 moving contact ya kasa a close position. T3 – T2 shine overloading period na wasu contacts (moving and fixed contact). Ba lokacin da T3 moving contact ya bounce back little bit and then again comes to its fixed closed position, after time T4.

Duk da haka, muna nuna yakin da take da tripping. Idan a lokacin da T5 karamin ya faru a kan trip coil na circuit breaker. Ba lokacin da T6 moving contact ya faru zuwa opening the contacts. Ba lokacin da T7, moving contact ya kasa fixed contact. Lokaci (T7 – T6) shine over lapping period.

Ba lokacin da T8 moving contact ya kasa final open position, amma ban da rest position saboda mechanical oscillation. Ba lokacin da T9 moving contact ya kasa rest position. Wannan ya nuna wa standard da remote control circuit breaker.

Circuit Breaker Opening Operation Requirement

Ana bukatar circuit breaker ya zama da open position da ma'ana. Saboda hakan, ana iya limita erosion da kuma interrupt faulty current da ma'ana. Amma total travel distance na moving contact ba da yawa da necessity of interruption of faulty current, amma contacts gap needed to withstand the normal dielectric stresses and lightning impulse voltage appears across the contacts when the CB is at open position.

Babu da need for carrying the continuous current and for withstanding a period of arc in circuit breaker, makes it necessary to use two sets of contacts in parallel one the primary contact which is always made of high conductive materials such as copper and the other is arcing contact, made of arc resistance materials such as tungsten or molybdenum, which has much lower conductivity than primary contacts.

During opening circuit breaker operation, the primary contacts open before the arcing contacts. However, due to the difference in the electrical resistance and the inductor of the electrical paths of the primary and arcing contacts, a finite time is required to attain total current commutation, i.e. from primary or main contacts to arcing contact branch.

So when the moving contact starts traveling from closed position to open position the contact gap gradually increases and after some time a critical contact position reaches which indicates the minimum conduct gap required for preventing re-arcing after very next current zero.
The remaining part of the travel is required only for maintaining sufficient dielectric strength between contacts gap and for deceleration purpose.

Circuit Breaker Closing Operation Requirement

During closing operation of circuit breaker the followings are required,

1. The moving contact must travel towards fixed contact at sufficient speed to prevent pre-arcing phenomenon. As the contact gap reduces, arcing may start before contacts are closed finally.

2. During closing of contacts, the medium between contacts is replaced, hence sufficient mechanical power to be supplied during this circuit breaker operation to compress dielectric medium in the arcing chamber.

3. After hitting fixed contact, the moving contact may bounce back, due to repulsive force which is not at all desirable. Hence sufficient mechanical energy is to be supplied to overcome repulsive force due to closing operation on fault.

4. In spring-spring mechanism, generally tripping or opening spring is charged during closing operation. Hence sufficient mechanical energy also to be supplied to charge the opening spring.

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