Advertisement
I
= prior load current.
P
In fact, the cold curve is simply a special case of the hot curve where prior load current I
for the situation where a cold system is switched on to an immediate overload.
Figure A-3 shows a typical thermal profile for a system which initially carries normal load current, and
is then subjected to an overload condition until a trip results, before finally cooling to ambient
temperature.
θ
(%)
100%
Overload Current
Condition
Normal Load
Current Condition
t (s)
Figure A-3
⎯ 280 ⎯
6 F 2 S 0 8 4 2
= 0, catering
P
Trip at 100%
Cooling Curve
Advertisement
