Overload Protection of Mains Electrical Circuits by Robert Wall

A new guide by Robert Wall on overload protection of mains electrical circuits.

Robert Wall writes:

The fundamentals.

All electrical circuits must have some means of protecting against overload. This may be done by including a fuse or circuit breaker in the circuit, or the protection may be designed in to the supply that is feeding the circuit. We will only consider fuses and circuit breakers, as these are most likely the device that will be encountered in a normal environment.

How to determine the ratings.

First, you need to know the current that the load demands, under all conditions. You then need to choose a fuse or circuit breaker that will not blow (or trip) when carrying that current, but with only the smallest safety margin under worst-case conditions. Finally, you must choose everything in between – cable, switches, plug & sockets, etc – so that each will safely carry the current that will guarantee that the fuse will blow, or the circuit breaker will trip, under all conditions (paying particular regard to ambient temperature and the ability of the cable expecially to stay cool, i.e. it must not be buried in insulation).

Read the full guide here: Overload Protection of Mains Electrical Circuits
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