Toshiba GRL150-100 Series Instruction Manual page 153

I = prior load current.
P
In fact, the cold curve is simply a special case of the hot curve where prior load current I
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
⎯ 152 ⎯
6 F 2 S 0 8 2 8
= 0, catering for
P
Trip at 100%
Cooling Curve