Original poster: Rob Maas <robm@xxxxxxxxx>
Tesla list wrote:
The coupling coeff. k can be calculated from the relation
k = SQRT(1 - i_0/i_short)
i_0 is - at a given primary voltage V_p - the primary current drawn
by the transformer when the secundary winding is open
i_short is - again at primary voltage V_p - the primary current, but
now the secundary winding is shortened.
You can make a series of measurements for a certain range of V_p.
You will then observe that in the lower range of V_p the value of
k will rise rather steeply to its nominal value; increasing the
value to the rated value of V_p of the transformer the value of
k will taper off slightly.
Typical value of k for an NST is about k = 0.95
If it is a 230V transformer, the value of k at 50-75 V may be around
k = 0.90; at V_p = 150 V, the value of k may reach its max. value of
say k = 0.955; by increasing V_p to 230 V, k may drop to 0.950.
See the 'transformer' link in
http://myweb.tiscali.co.uk/teslatutorial/index.htm
for more details.
Success with the measurements!, Rob