How arc take place in circuit breaker?

Answer 1

All circuit breakers try to achieve the same thing: ensure that the rate of increase of dielectric strength exceeds the rate of increase of potential gradient across the gap between the separating contacts.

Explained in another way, the rate at which energy is developed by the arc must be exceeded by the rate at which energy is dissipated through heat transfer.

This can be achieved in numerous ways:

• reduction in arc temperature -which reduces vapourization of contact metals and ionisation of insulating medium.
• reduction in potential gradient -increasing contact separation distance.
• constriction of the arc -by insulating medium pressure, which reduces cross-sectional area of arc, and increases its resistance.
• increasing medium dielectric strength -by replacing contaminated insulation medium.
• speed of operation -minimising energy build up (I2Rt).
• utilising 'current zero' -utilising the natural cut-off point for a.c. current.

All practical circuit breakers utilise a combination of the above methods.

Answer 2

When an electrical circuit is opened an arc is created. This is because of the collapsing magnetic field cutting the conductor and inducing a current in the same direction the current was flowing before the circuit was opened. The breaker is designed with arc shoots to extinguish the arc before it becomes hot and dangerous See related links below

Answer 3

potential difference between contects

Answer 4

Loose connections or a broken breaker.