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MPC2000+ Technical Manual
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
2
(uB)
However the minimum trip time is 1 second and the minimum pick up is the same as the setting "unbalance Current"
above.
P&B Engineering
where
To = time constant setting
uB = The unbalance in %.
LOWER
LIMIT
EXAMPLE
5 %
20 %
120
70
To=20
20
10
1
0.1
10
20
5
% UNBALANCE
ISSUE 7 28/9/99
UPPER
LIMIT
40%
To=70
To=120
30
50
40
100
200
Page 21
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