Magnetizing current in a transformer is non-sinusoidal due to the non-linear nature of the transformer’s magnetic core. The core material exhibits a non-linear B-H (magnetic flux density versus magnetic field strength) characteristic, meaning that as the magnetic field strength increases, the magnetic flux does not increase proportionally. This non-linearity causes distortion in the magnetizing current, resulting in a waveform that deviates from a pure sine wave.
The current waveform is non-sinusoidal in the BH curve because the relationship between magnetic flux density and magnetic field strength in the core material is non-linear. When an alternating voltage is applied, the varying magnetic field causes the core to move through its hysteresis loop, which is not a straight line. This results in a magnetizing current that contains harmonics, deviating from a pure sinusoidal waveform.
The no-load current in a transformer is non-sinusoidal. At no load, the current drawn by the transformer, known as the magnetizing current, is primarily used to magnetize the core. Due to the non-linear magnetization characteristics of the core material, this magnetizing current is distorted and contains harmonic components, making it non-sinusoidal.
Magnetizing current in a transformer is the current required to establish the magnetic flux in the core. It is present even when there is no load connected to the secondary winding. This current compensates for the core losses and maintains the magnetic field necessary for transformer operation. Because of the core’s non-linear characteristics, the magnetizing current typically includes harmonic components and is non-sinusoidal.
During the open circuit test of a transformer, the current observed is not sinusoidal due to the core’s non-linear magnetic properties. In this test, the transformer operates with no load, and the primary current consists mainly of the magnetizing current. The non-linear B-H relationship of the core material causes the magnetizing current to have harmonic distortion, resulting in a non-sinusoidal waveform.