by the short-circuit current fl owing through it to trip its circuit breaker by
direct mechanical action. These devices are operated by (1) an electromagnetic
force created by the short-circuit current fl owing through the trip device
coil (the trip coil is usually connected in series with the electrical circuit or in
some instances to the secondary of current transformers) or (2) a bimetallic
strip actuated by the head generated by the fault current. The bimetallic strip
is usually connected in series with the circuit.