Page 47 - Application Guide Semiconductor Fuse Link

Appendix

(c) other principal symbols used in this guide

General

r.m.s. root-mean-square
In nominal continuous current rating A
In’ continuous current rating in a real-world application A
I instantaneous curren A
2
2
I t integral of i over a specifi ed period of time A s
temperature ºC
o reference ambient temperature ºC
a ambient temperature in a real-world application ºC

F instantaneous voltage across fuse V
2
K I t correction factor (for applied voltage)
VPK peak arc voltage of fuse V
2
Meyer’s constant A s mm- 4
KM
A cross-sectional area mm 2

A.C. circuit

V r.m.s. source voltage V
I r.m.s. prospective (available) short-circuit current A
f frequency Hz
angular frequency ( = 2 f ) rad/s
L inductance H
R resistance
angular instant at which short-circuit occurs w.r.t. voltage rad
wave
-1
circuit power-factor angle (= tan vv L/R ) rad

X circuit inductive reactance (= vv L )

D.C. circuit

VDC source voltage V
T circuit time constant (= L/R ) s
IRMS effective r.m.s. current for a specifi ed time A

cyclic loading

r.m.s. current which will cause melting in a specifi ed time A
IMELT
IRMS r.m.s. current over a complete cycle A
pu RMS per-unit r.m.s. loading ( = IRMS /In )
KN , x, y parameters in cyclic endurance equation
N number of cycles
highest peak-to-peak temperature excursion within fuse °C

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