What is meant by Current Chopping?
Answer: Current Chopping is a phenomenon of current interruption before the natural current zero is reached.
Why Isolation switches are provided along with the circuit breakers?
Answer: Isolation switches are provided for separating the disconnected element from the live portion of the system for the purpose of safety.
Why asymmetrical breaking current is higher than the symmetrical breaking current in a circuit breaker?
Answer: Asymmetrical breaking current is the rms value of the combined sum of the dc and ac components of the short circuit current at the instant of separation of the breaker contacts while symmetrical breaking current is the rms value of the ac component alone. Thus asymmetrical breaking current is higher than the symmetrical breaking current.
What is recovery voltage in circuit breaker?
Answer: Recovery voltage in circuit breakers is defined as the power frequency rms voltage which appears across the breaker contacts after the transient oscillations die out and the final extinction of the arc has resulted in all the poles of the circuit breaker.
It is the voltage developed after the arc extinction is competed
When does an arc extincts?
Answer: If the rate of rise of re-striking voltage (RRRV) is less than rate of rise of dielectric strength between the breaker contacts arc will not sustain and extincts
What is re-striking voltage?
Answer: The Re-striking voltage may be defined as the resultant transient voltage which appears across the breaker contacts at the instant of arc extinction
For an Resistive Load and Inductive load considered for switching operation of circuit breaker, Switching of which load is difficult and Why?
Answer: In case of switching resistive load, current and voltage will be in phase i.e,when during current zero voltage also will be zero in case of resistive load. Hence the voltage at the breaker terminals during arc extinction is zero or minimal. On the other hand, for switching inductive load during current zero voltage across the breaker will be maximum. This results in re-striking of arc once again. Therefore switching inductive load will be difficult
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