From: mynamespacedbydots@xs4all.nl   
      
   "Don Pearce"   
   >>   
   > Could you explain these tests in a little more detail? I'm not sure   
   > why the inductance appears to be dependent on the voltage.   
      
      
   It's due to hysteresis losses of ferromagnetic materials like the lamination   
   in transformers.   
      
   Take f.e. a mains transformer and measure the current trough the primary,   
   while the secondary is open:   
      
   1) at mains voltage, f.e. 230Vac   
   2) at about 1/10 of the first, f.e. 24Vac.   
      
   Calculate Z from Vac/Iac and XL from Sqrt(Z^2 - Rdc^2).   
   Than calculate L from XL/(2.pi.f)   
   Usually Rdc can be ignored, so XL practically equals Z.   
      
   3) you will find two quite different figures for the inductance.   
      
   Gio   
      
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