How to Measure Inductor/Reactor Coil Impedance??

That's the lowest voltage 3-phase system I have ever seen.

We have tested with 3 phase variac applying 31V/phase ...making star point at other ends of all three reactor coil

Whatever you do: Don't get zapped!

Do you have a work permission to play around with your reactor coils?

Given your history I would stick to calculations rather than hands on measurements.

Is this a bicycle generator with three phases?

Impedance is a function of inductance and frequency. There are unlimited resources for reference that indicate the relationship between them; it is even part of the school Physics syllabus these days.

Bingo! Exactly what the textbooks say! :-)

Sigh. There is so much information available right under our fingers. From how to does one make three phase power measurements from a test equipment company to free textbooks from a reputable science literature distributor. Still people ask questions about three phase power in a way that demonstrates that they don't get it.

Try not to hurt anyone.

If this is for a balanced three phase system doesn't it bother you that the readings vary so much? The coils should be closely matched, if they are physically the same then there must be some variance in the connections and/or your test setup. Also if you want an accurate impedance you should not use the DC resistance, use the AC resistance at the operating frequency which will be different due to the skin effect.