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When no load operation, taking into account the equivalent "p" circuit and the Amper-turns equation, the absorbed current, can be approximated to be only the magnetising current

.

The line-to-line voltage, the phase current (U₁, I₁) and the active power (P₁₀) are measured for no load operation conditions (Figure 3).

Figure 3

The impedance of the magnetising circuit is computed and after separation of the stator Joule looses and mechanical looses, the equivalent resistance of the magnetising circuit is determined (considered to be a series equivalent circuit). It results

R_m = 2,31 W.

The reactance of the magnetising circuit is then computed. It results immediately the magnetising inductance

L_m = 0,3 H.

Note.

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