Toshiba GRT100 Series Instruction Manual page 227

where:
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 N-2 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.

()
100%

()
100%
80%
Figure N-2 (2) Thermal curve with Prior Load Current (
Overload Current
Condition
Normal Load
Current Condition
t (s)
Figure N-2 (1) Thermal Curve without Prior Load Current
Normal Load
Current Condition

226
Trip at 100%
Overload Current
Condition
t (s)

6 F 2 S 0 7 8 9
= 0, catering for
P
Cooling Curve
Trip at 100%
Cooling Curve
=
80%)