GE P642 Technical Manual page 221

P64x
and the IEC 60255 IDMT Reset equation is:
β
 
t T
=
 
r
α
1 M
−
 
where:
t is the operating time
●
op
t is the reset time
●
r
T is the Time Multiplier setting
●
M is the ratio of the measured current divided by the threshold current (I/Is)
●
β is a constant, which can be chosen to satisfy the required curve characteristic
●
● α is a constant, which can be chosen to satisfy the required curve characteristic
C is a constant for adding Definite Time (Definite Time adder)
●
● L is a constant (usually only used for ANSI/IEEE curves)
The constant values for the IEC IDMT curves are as follows:
Curve Description
IEC Standard Inverse Operate
IEC Standard Inverse Reset
IEC Very Inverse Operate
IEC Very Inverse Reset
IEC Extremely Inverse Operate
IEC Extremely Inverse Reset
UK Long Time Inverse Operate*
BPN (EDF) Operate*
UK Rectifier Operate*
FR Short Time Inverse Operate
Rapid Inverse (RI) characteristic
The RI operate curve is represented by the following equation:


t K
=

op
0 339 .

−

where:
t is the operating time
●
op
● K is the Time Multiplier setting
M is the ratio of the measured current divided by the threshold current (I/I
●
Note:
* When using UK Long Time Inverse, BPN, UK Rectifier, FR Short Time Inverse, or RI for the Operate characteristic, DT (Definite
Time) is always used for the Reset characteristic.
P64x-TM-EN-1.3
b constant
0.14
8.2
13.5
50.92
80
44.1
120
1000
45900
0.05

1


0 236 .

M

Chapter 9 - Current Protection Functions
a constant
0.02
6.45
1
2.4
2
3.03
1
2
5.6
0.04
)
s
L constant
0
0
0
0
0
0
0
0.655
0
0
197