Impedance Frequency Analysis of Stator Winding of Electric Motors using High-Frequency Equivalent Circuit

This study aims to develop a technique for simulating high-frequency circuit to estimate the voltage distribution within the winding when surge voltages enter the stator insulation system of rotating electric motors. The motor under consideration in this paper is a three-phase induction motor with a rated output of 75
$\text{kW}$
and a rated voltage of
$3\text{kV}$
. The winding consists of two parallel wound type with 10 turns and 16 windings per phase featuring 4 poles. To measure distributed voltage at any point, the three-phase winding and neutral were disconnected, and measurement leads were attached to each turn winding. By analyzing the structure and arrangement of the motor stator windings, circuit constants including the resistance
$R$
, selfinductance
$L$
, mutual inductance
$M$
, and capacitance
$C$
were determined. Using these circuit constants, a lumped constant highfrequency circuit model was constructed. the frequency characteristics of impedance
$Z(f)$
of the winding were obtained by performing transient analysis simulations with LT-Spice software. The calculated
$Z(f)$
values were then compared against the measured ones of the actual stator winding, validating the highfrequency circuit model. The results indicated a good agreement between the calculated and measured
$Z(f)$
values, suggesting the reliability of the developed high-frequency circuit model for the subject motor.