Re: Mutual Inductance and Coupling Measurement

From: 	Edward V. Phillips[SMTP:ed-at-alumni.caltech.edu]
Sent: 	Friday, August 08, 1997 2:50 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re:  Mutual Inductance and Coupling Measurement

	Here is a pretty fundamental way to measure the mutual
inductance, provided you have a millivoltmeter.  Feed a known
60 cycle current (say power line in series with 100 watt light
bulb) through one winding and measure the induced voltage
across the other.  Suppose, for instance, that the mutual
inductance is 100 microhenries.  This represents a reactance
of 0.0377 ohms at power line frequency, so the voltage will
be omega x M x I = 377 x 100 E-6 x 1 =37.7 millivolts.
	Having measured M the coupling factor k is the 
mutual inductance M divided by the square root of L1 x L2,
where L1 and L2 are the winding inductances.