Correlation between inrush current and system impedance
Correlation between inrush current and system impedance
(OP)
I am aware that source impedance is a determining factor when considering inrush. I was wondering if there is a correlation between the two that would provide one with a ballpark of what the inrush current will be more or less based on source impedance and transformer rated current (Ir).
I am aware that the inrush current is also dependent on other factors such as transformer design, core material, point-on-wave of energisation.
Thus allowing for all these (assuming worst case) and given that the primary voltage is x volts, Ir = y amps, source impedance = Zs (positive sequence) is there a way of deriving a ballpark figure for the inrush current?
Thanks.
I am aware that the inrush current is also dependent on other factors such as transformer design, core material, point-on-wave of energisation.
Thus allowing for all these (assuming worst case) and given that the primary voltage is x volts, Ir = y amps, source impedance = Zs (positive sequence) is there a way of deriving a ballpark figure for the inrush current?
Thanks.






RE: Correlation between inrush current and system impedance
RE: Correlation between inrush current and system impedance
Thanks.
RE: Correlation between inrush current and system impedance
MikeL.
RE: Correlation between inrush current and system impedance
I downloaded this file from this forum a long time ago.
Please see attached file.
RE: Correlation between inrush current and system impedance
-Air core reactance of winding on which energized- depends on inductance ie diameter and length of winding(ie kVA rating)
- Instant of switching on the voltage sine wave (max at zero &min at max voltage)
- Magnitude and polarity of residual flux in core
- Coupling factor -depending on connection (star/delta) and core construction (single phase,3 phase 3 limb or 5 limb)
RE: Correlation between inrush current and system impedance
Iinrush = Ipeak / (1 + Ipeak * Xsource)
All values in per unit.
Source:
https://books.google.de/books?id=qW_OBQAAQBAJ&...
RE: Correlation between inrush current and system impedance
RE: Correlation between inrush current and system impedance
I peak = peak of first cycle of inrush current with zero source reactance. I inrush= Peak of inrush with source impedance of X. Westighouse(now ABB) handbook is very clear on this.It is assumed that inrush will come down linearly with applied voltage. But normally source impedance too low compared to transformer impedance and such corrections are never applied.