Woodward SEG HighPROTEC MRA4, Device Manual

Page: 323 / 510

I2>-Protection Module – Unbalanced Load Protection [ANSI 46]
If the heat amount is not reduced when the permitted unbalanced load current is overshoot again, the remaining
heat amount will cause an earlier tripping.
EN MRA4 04/09 Page 323
1 10
0.1
1
10
100
1
.
10
3
1
.
10
4
K=200
K=100
K=50
K=20
K=10
K=5
K=1
Typical NPSI-Relay Operating Curves
(Curren t I2/I2s (%))
T
im
e
(s
)
10000
0.1
t I2% 0.5
,
200
,
( )
t I2% 0.5
,
100
,
( )
t I2% 0.5
,
50
,
( )
t I2% 0.5
,
20
,
( )
t I2% 0.5
,
10
,
( )
t I2% 0.5
,
5
,
( )
t I2% 0.5
,
1
,
( )
10 1 I2%
t = Tripping delay
t -cool = Cooling time constant
Theta
0
= Heat (thermal) energy before the cooling down has started
Theta(t) = Momentanous heat (thermal) energy
Legend: