Question

A 1,500kVA dry type transformer has the following characteristics at rated power:

Primary Voltage V1=11kV;
Secondary Voltage V2=380 V;
Primary Copper Loss =7 kW;
Secondary Copper Loss =9 kW;
No-load Losses (with THD I<5%)=5.5 kW;
Rated true power factor =0.95.

(a) What constitute the No-load Losses in a transformer? Why is it dependent on the Total Harmonic Distortions of current?

Answer 1

No-load losses in a transformer are primarily due to core losses, including hysteresis and eddy current losses, and are influenced by the Total Harmonic Distortion (THD) of current because harmonics increase the energy dissipation within the core material.

Step-by-step explanation:

The no-load losses in a transformer refer to the energy dissipated when the transformer is energized but no load is connected to its secondary. These losses consist primarily of core losses, which include hysteresis losses and eddy current losses in the core material. The hysteresis losses are due to the lagging behind of the magnetic domains in the core material when the magnetic field changes, while eddy current losses are due to circulating currents within the core material itself, which create heat. No-load losses are dependent on the Total Harmonic Distortion (THD) of current because harmonics can increase eddy current and hysteresis losses due to the increased magnetic flux densities and higher frequencies involved, which enhances energy dissipation within the core.