Iec Thermal Overload Protection Curves - DEMA 400 Series User Manual

4.3.1.2

IEC Thermal Overload Protection Curves

IEC Thermal Overload Protection formula and sample curves according to this formula are
given below. Formula characteristic is determined by the Te, k, Iθ, %θp and %θtrip
parameters. When setting ranges for these parameters are considered, it is calculated that 400
Series relay can run 1,540,000 unique IEC Thermal Overload Protection curves; for its
impossible to demonstrate all of the curves on a chart, sample curves are given on the below
chart to express an overview of the characteristic
I
( )
k×I
Θ
t= T × log
e
2
e
I
( )
k×I
Θ
45
2
-%Θ
p
-%Θ
trip