Selecting the Right Circuit Breaker and Its Type

Working Mechanism:

Arc Phenomena:

By F1jmm — Own work, CC BY-SA 4.0, Link

Arc Extinction Methods:

90% OFF — Power System Protection Fundamentals

Categories of Circuit Breakers:

Important Parameters in the Selection of Circuit Breakers:

  • Interrupting capacity /KA: it is the maximum current in which the breaker is designed to interrupt safely at a certain voltage.
  • Instantaneous pickup: The settings at which the circuit breaker operates immediately without any intentional delay. All MCCBS and ICBs possess instantaneous trip settings, while for PCBS it is optional.
  • Short Time settings: It is the characteristic of a circuit breaker to remain closed for a time interval under a range of high fault currents. It is an important factor in achieving selective coordination among circuit breakers.
  • Long Time settings: It is the setting of the circuit breaker to determine the time duration to allow a certain overload current to flow before tripping. (for current magnitudes lesser than short time or instantaneous pickup).
  • Continuous Amps: It is the current which the device will carry without tripping or overheating.
  • Frame size: Frame size indicates the physical size of the breaker as well as the maximum continuous current it can tolerate.
  • Rated KV: It indicates the highest system voltage which the circuit breaker can sustain.
  • Rated KVA or MVA: An important characteristic of a circuit breaker is its breaking or rupturing capacity. It is the maximum current that a circuit breaker is capable of breaking at a given voltage and under specific conditions e.g. power factor.

Selection of Circuit Breaker According to Its Applications/Tripping Device:


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AllumiaX Engineering

AllumiaX Engineering

Leaders in Industrial & Commercial Power Systems Engineering