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Inductor inrush current stress

AC voltage source is connected to the inductor. Then AC power is applied, inrush current may be considerably higher than regular, and corresponding magnetic forces may cause higher mechanical stresses in the inductor assembly.

Problem Type:
Axisymmetric multiphysics problem of transient magnetics coupled to stress analysis.

Geometry:
Inductor inrush current stress AC voltage source is connected to the inductor Core Insulation Winding AC 18 V ~ 31 mm 38 mm Ø 12 mm Ø 36 mm

Given:
Relative magnetic permeability of the steel core μ=2000;
Electric conductivity of the winding (copper) g = 56 MS/m;
Number of turns w = 600;
Applied voltage value (amplitude) U = 18√2 V;
Frequency f = 60 Hz.

Task:
Calculate the peak current value and mechanical stress in the inductor winding.

Solution:
The current wave period is T = 1 / f = 16 ms. We choose the time step of 1 ms that guarantees a smooth time-plot. Nine periods are simulated (150 ms).

Results:
The peak current value is 1.8 A (+65% to the rated value) appears 7ms after switching the voltage on. The color map of mechanical stress in the coil is shown below.

Inductor inrush current stress

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