Making and breaking currents of 3-phase AC circuit breakers in power system are respectively in what form

Electrical Engineering XYZ MCQs

Making and breaking currents of 3-phase AC circuit breakers in power system are respectively in what form:

1. RMS and Instantaneous value
2. RMS and RMS value
3. Instantaneous and RMS value
4. Any of the above

Correct answer: 3. Instantaneous and RMS value

Explanation: In a 3-phase AC circuit breaker in a power system, the making and breaking currents occur in different forms.

1. Making Current: The making current is the current that flows at the instant the circuit breaker closes to connect the circuit. This current is typically characterized by its instantaneous value because it is the current at the exact moment of closure.
2. Breaking Current: The breaking current is the current that flows at the instant the circuit breaker opens to disconnect the circuit. This current is often characterized by its RMS (Root Mean Square) value because it represents the effective or average value of the current over a complete cycle.

Therefore, the making current is in instantaneous form, and the breaking current is in RMS form. The correct option is “Instantaneous and RMS value.”