Thytronic NA11 User Manual

141
NA11 - Manual - 02 - 2009
APPENDIX
8.3 APPENDIX A3 - Inverse time - RECTIFIER, I
2
t and EM curves
Mathematical formula
The mathematical formula for RECTIFIER, I-squared-t (I
2
t) and Electromechanical curves (EM) is:
[1]
Where:
t = operate time (in seconds)
t
I>inv
= setting time multiplier (in seconds)
I = input current
I>
inv
= threshold setting
K = coeffi cient:
K = 2351 for RECTIFIER curve (RI)
K = 16 for I
2
t curve
K = 0.28 for Electromechanical curve (EM)
α = curve shape constant:
α = 5.6 for RECTIFIER curve (RI)
α = 2 for I-squared-t (I
2
t) curve
α = -1 for Electromechanical curve (EM)
A = coeffi cient:
A = 1 for RECTIFIER curve (RI)
A = 1 for I-squared-t (I
2
t) curve
A = -0.236 for Electromechanical curve (EM)
B = coeffi cient:
B = 1 for RECTIFIER curve (RI)
B = 0 for I-squared-t (I
2
t) curve
B = -0.339 for Electromechanical curve (EM)
For all inverse time characteristics, following data applies:
Asymptotic reference value (minimum pickup value): 1.1 I>
inv
Minimum operate time: 0.1 s
Range where the equation is valid:
[2][3]
1.1 ≤ I/I>
inv
≤ 20
If I> pickup ≥ 2.5 I
n
, the upper limit is 50 I
n
Note 1 Symbols are concerning the overcurrent element. The comprehensive overview of the inverse time characteristics concerning the 50/51 and
50N/51N elements is dealt within the PROTECTIVE ELEMENTS section
Note 2 When the input value is more than 20 times the set point , the operate time is limited to the value corresponding to 20 times the set point
Nota 3 With setting more than 2.5 In for the 50/51 elements and 0.5 IEn for the 50N/51N elements, the upper limit of the measuring range is limited to 50
In and 10 IEn respectively.
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t =
t>
inv
·
A·(I/I>
inv
)
α
-B]
K
t =
t>
inv
·
A·(I/I>
inv
)
α
-B]
K

Thytronic NA11 Specifications

General

Brand	Thytronic
Model	NA11
Category	Relays
Language	English