What is meant by b, c, d, k and z curves in mcbs full form?
Answers
MCB (Miniature circuit breaker) is a resettable device designed to protect a circuit from short circuits and overcurrents. Trip curves of MCB’s (B, C, D, K and Z curves) tell us about the trip current rating of Miniature Circuit breakers. Trip current rating is the minimum at which the MCB will trip instantaneously. It is required that the trip current must persist for 0.1s
TRIP CURVE CLASS B
The MCB with class B trip characteristics trips instantaneously when the current flowing through it reaches between 3 to 5 times rated current. These MCBs are suitable for cable protection.
TRIP CURVE CLASS C
MCB with class C trip characteristics trips instantaneously when the current flowing through it reaches between 5 to 10 times the rated current. Suitable Domestic and residential applications and electromagnetic starting loads with medium starting currents.
TRIP CURVE CLASS D
MCB with class D trip characteristics trips instantaneously when the current flowing through it reaches between Above 10(excluding 10) to 20 times the rated current. Suitable for inductive and motor loads with high starting currents.
TRIP CURVE CLASS K
MCB with class K trip characteristics trips instantaneously when the current flowing through it reaches between 8 to 12 times the rated current. Suitable for inductive and motor loads with high inrush currents.
TRIP CURVE CLASS Z
MCB with class Z trip characteristics trips instantaneously when the current flowing through it reaches between 2 to 3 times the rated current. These type of MCBs are highly sensitive to short circuit and are used for the protection of highly sensitive devices such as semiconductor devices.
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