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Arc Voltage: The Voltage drop across the arc is called Arc Voltage .

Arc Extinction. Arc Voltage: The Voltage drop across the arc is called Arc Voltage . Arc Quenching: ( C.B ) The Arc Produced not only delays the current interruption process but it also generates enormous heat which may cause damage to the system or to the circuit breaker itself.

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Arc Voltage: The Voltage drop across the arc is called Arc Voltage .

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  1. Arc Extinction Arc Voltage: The Voltage drop across the arc is called Arc Voltage.

  2. Arc Quenching: ( C.B ) • The Arc Produced not only delays the current interruption process but it also generates enormous heat which may cause damage to the system or to the circuit breaker itself. • Therefore main problem in a C.B is to extinguish the arc within the shortest possible time so the heat generated by it may not reach a dangerous value.

  3. ARC PHENOMENON During arcing period, the current flowing between the contacts depends upon the resistance. The greater resistance smaller the current that flows between the contacts. The arc resistance depends upon i) Degree of ionisation ( Arc resistance increases with the decrease in number of ionised particles b/w the contact ) ii) Length of Arc ( Arc resistance increases with the length of arc ) iii) Cross section of Arc ( Arc resistance increases with the decrease in X- section of the arc )

  4. The factors that are responsible for maintenance of arc between the contacts are: i) Potential Difference between the contacts. ii) ionised particles between the contacts.

  5. Methods of Arc Interruption • There are two methods of Arc Interruption or Extinction are i) High resistance interruption ii) Current zero interruption High resistance interruption The arc resistance can be increased by cooling, lengthening, reducing x- section and splitting the arc.

  6. It is employed for low power AC and DC circuit breakers. Current zero interruption There are two theories to explain the zero current interruption of the arc. i) Recovery rate theory ( Slepain’s Theory ) ii) Energy balance theory ( Cassie’s Theory )

  7. Recovery rate theory

  8. Energy balance theory

  9. Arc Extinction in oil Circuit Breaker In case of oil circuit breaker the opening of contact which heats the oil surrounds the contact due to arc which causes hydrogen gas bubble to evolve and its removes the heat from the surface. If the rate of heat removal is faster than its generation then the arc is extinguished.

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