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Transformer Riddle No.64 - Harmonic content in transformer noload current
Can you please tell me is there any possibility that 5th harmonics can be higher than 3rd harmonics in outer two phases of the transformer?

Kindly reply to me it is very urgent.

Author : Sreelatha - From: India
 
#1
Wed, March 30th, 2011 - 15:20
No because:

As you know the figure of transformer magnetizing current goes to square wave related to degree of its core saturation.
In ORTHOGONAL FUNCTIONS, Φi, defined in a≤x ≤b is called orthogonal (or unitary, if complex) if it satisfies the following condition:



The Fourier series of an even function contain only cosine terms and may also include a DC component. Thus, the coefficients bi  are zero.
The Fourier series of an odd function contain only sine terms. The coefficients ai are all zero.
The Fourier series of a function with half–wave symmetry contain only odd harmonic terms with ai = 0 for i = 0 and all other even terms and bi = 0 for all even values of i.

For example consider the periodic function of square function in Figure below



Applying the orthogonality relations , we find that all ai coefficients are zero.  We also can  determine the coefficients associated with the sine function in this series. For example, the first term, b1, is calculated as follows:



As you see in square wave the peak amount of bigger harmonic will be smaller (bi=4/iπ) in comparison of smaller harmonic. 
Author : Hamid - From: Iran
 
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