Thytronic NA10 User Manual

APPENDIX
132
NA10 - Manual - 04 - 2022
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 = coefficient:
• 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 = coefficient:
• A = 1 for RECTIFIER curve (RI)
• A = 1 for I-squared-t (I
2
t) curve
• A = -0.236 for Electromechanical curve (EM)
B = coefficient:
• 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.
t =
t>
inv
·
A·(I/I>
inv
)
α
-B]
K

Thytronic NA10 Specifications

General

Brand	Thytronic
Model	NA10
Category	Relays
Language	English