Overload Trip Time Calculation
45
Note: In overload procedure, current is limited to 5 x Motor FLA to prevent saturation in calculation, so trip time at 5 or
8 times motor FLA will be identical.
The approximate
trip time is given in the following equation:
OLT = Overload Trip setting (default 115%)
OLD = Overload Delay setting – trip delay at 5 x Motor FLA,
(default 4 sec).
Example 1: Motor FLA = 80A, actual current = 120A,
I
%
= 120 x 100 / 80 = 150%
If settings are as in default then
Example 2: Same motor and setting, but current is 400A,
I
%
= 400 x 100 / 80 = 500%
If settings are as in default then
Example 3:
Motor FLA = 80A, actual current = 200A, Overload Delay (OLD) = 10
I
%
= 200 x 100 / 80 = 250%
Seconds)(In
6
OLD
OLTI
000,375,1
Time Trip O/L
2
2
%
×
−
=
FLAMotor
100
Current Actual I :Where
%
×=
sec. 99
6
4
151501
000,375,1
Time Trip O/L
22
=×
−
=
sec. 4
6
4
151500
000,375,1
Time Trip O/L
22
=×
−
=
sec. 47
6
10
151250
000,375,1
Time Trip O/L
22
=×
−
=