
240 Shipboard Electrical Power Systems
10.2 OVERLOAD PROTECTION
The fuse and circuit breaker clears fault only if the overcurrent is greater than 200%
of its own rated current. That leaves a protection gap between 115% overload allowed
in most equipments for an hour or two and 200% overload. This gap is bridged by
the overload protection. In its simplest and often used form shown in Figure10.6,
it consists of a pair of bimetallic links that remains closed in normal operation, but
deforms differentially to open the contacts when overheated.
Ambient Temperature
–50
80
60
100
40
120
0 25 –25 50 75 100°C
Standard and fast-acting fuses ...