Which type of MCB tripping curve is most appropriate for protecting standard domestic lighting circuits?
Type B MCB
Miniature circuit breakers are classified by tripping curves that describe how many times the rated current must flow before the magnetic element trips instantaneously, matching the breaker to the inrush behaviour of the load.
A Type B MCB trips magnetically at about three to five times its rated current, which is ideal for circuits with little switch-on surge such as domestic lighting and general-purpose socket outlets.
Because lighting and resistive loads draw only a small initial current, the low Type B threshold gives fast protection against faults without nuisance tripping.
A Type C MCB trips at about five to ten times rated current, chosen for moderately inductive loads like small motors and fluorescent banks, so it is less sensitive than needed for plain lighting.
A Type D MCB trips at about ten to twenty times rated current, suited to high-inrush loads such as transformers and large motors, far more than a lighting circuit requires.
Type A is a very sensitive curve used mainly for semiconductor and measuring circuits and is not a standard general-purpose domestic type.
Hence, the answer is Type B MCB.
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