compendium
Non-sinusoidal magnetising current of a transformer

The magnetising current of a transformer (at a sinusoidal primary voltage) contains odd-numbered harmonics of a higher order (overtones).
The modulation of the magnetization characteristic far into the saturation range is typical for transformers used in power engineering (B > 2T).
If the magnetization characteristic can be described sufficiently by the polynomial (with zero-symmetry) 		 
(55)
(a frequently used approximation) then the spectrum of the magnetising current also contains the 3rd, 5th 7th and 9th harmonic besides the fundamental wave (1st harmonic).
For a sinusoidal voltage 		(56)
 
follows the magnetic flux density-time function  
(57)
and because of  
(58)
one obtains  
(59)
and with Ampere´s law the conlusion above on the magnetising current.
Using the experiments on non-linear distortion one can watch the occurence of higher harmonics in the course of the magnetic field force H(t) at sinusoidal magnetic flux density B(t) (if the B-H characteristic is beeing modulated into the saturation range). In the case of measuring transformer (B = 0,03 ... 0,05 T) and pulse trasformer (B = 0,4 T) the dimensioning of the magnetic circuit ensures that the modulation remains in the linear part of the B-H-characteristic.