Thytronic NG10 - APPENDIX A3 - Inverse Time EM Curves; Mathematical Formula

APPENDIX
127
NG10 - Manual - 04 - 2022
8.3 APPENDIX A3 - Inverse time EM curves
 Mathematical formula
The mathematical formula for RECTIFIER, I-squared-t (I
2
t) and Electromechanical curves (EM) is:
Where:
• t = operate time (in seconds)
• t
E>inv
= setting time multiplier (in seconds)
• I
E
= input current
• I
E
>
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
E
>
inv
• Minimum operate time: 0.1 s
• Range where the equation is valid:
[1]
1.1 ≤ I
E
/I
E
>
inv
≤ 20
• If I
E
> pickup ≥ 0.6 I
En
, the upper limit is 12 I
En
Note 1 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
t =
t
E
>
inv
·
A·(I
E
/I
E
>
inv
)
α
- B
K