# 3 phase synchronous machine with salient rotor inductances and resistances measurement

I am trying to find if the following method to determine experimentally 'natural' inductances and resistances (not synchronous, transient, subtransient etc..) of a synchronous generator is valid theoretically.

As for practicality, it will depend I suppose on the capacity of the LCR meter to detect small inductances fluctuations due to rotor position.

Assuming a concentrated windings stator and a two pole salient rotor with brushed exciter :

For resistances, this is straightforward:

• Field resistance measurement: between both field leads.

• Stator single phase winding measurement: between phase and neutral point.

Inductances :

• Field self inductance measurement:

Shunt all stator phases to neutral point. Measure inductance and take average value after stepping the rotor a full rotation.

• Field to stator phase mutual inductance:

Shunt two phases to neutral. Measure field inductance while stepping the rotor to find the maximum. Take this value, and subtract the field self inductance. This gives the stator phase to field mutual inductance.

• Stator phase self inductance:

Shunt two phases to neutral, shunt the field winding. Measure the remaining phase inductance between phase and neutral. Rotate the rotor to find maximum minimum and average values. average is self inductance, (max - min)/2 is the self inductance component due to saliency effects.

• Stator phase to phase mutual inductance:

Shunt field. Shunt one phase to neutral. Measure inductance between the next phase and neutral, leaving the remaining phase lead disconnected. Rotate the rotor to find the minimum and maximum values. Compute average. Remove this average from stator self inductance, this gives the average mutual inductance between two phases, while (max-min)/2 gives the saliency inductance component.

• Dampers self inductances and mutual inductances with respect to the other windings:

Not measurable with an LCR meter, only through transient analysis.

Then one should take into account iron core losses due to the measurement done by LCR meters at around 120 to 160 kHz, which is not ideal for electric steel, so one should apply a correction factor.

• For now, the best I found is :eleceng.adelaide.edu.au/research/power/pebn/… which discourages the use of a LCR meter, not only because of skin effect, but because of low current used which makes the measure in a portion of the B/H curve that is not representative of the machine working conditions. The effect is a lower measured inductance Commented Aug 19, 2023 at 11:13