Technical Manual
P&B Engineering
ISSUE 7 28/9/99
Page
21
Current Unbalance Time Constant
This setting determines the time that the current may be unbalanced before a trip is initiated. The setting is adjustable
via the keypad. The value To has the range 20 - 120 seconds in steps of 1 second, the default value being 30 seconds,
and it refers to the inverse slope of the time verses %unbalance characteristic which has a reference point
corresponding to an Unbalance of 10%.
The unbalance trip function is an inverse-time characteristic of the form
T = 100 To
where
To = time constant setting
(uB)
2
uB = The unbalance in %.
However the minimum trip time is 1 second and the minimum pick up is the same as the setting “unbalance Current”
above.
5 %
20 %
0.1
1
10
40%
5
10
20
30
40
50
100
200
% UNBALANCE
LOWER
UPPER
LIMIT
LIMIT
EXAMPLE
To=120
To=20
To=70
20
70
120
Summary of Contents for MPC2000+
Page 4: ......
