The use of higher flux density in the transformer design

The correct answer is: B. reduces iron losses.

Iron losses are caused by the eddy currents and hysteresis losses in the transformer core. The higher the flux density, the greater the eddy current losses. However, the hysteresis losses are not affected by the flux density. Therefore, the use of higher flux density in the transformer design will reduce the iron losses.

The other options are incorrect because:

• A. The weight per kVA is not affected by the flux density.
• C. The copper losses are caused by the current flowing through the windings. The higher the flux density, the higher the current flowing through the windings, and therefore the higher the copper losses.
• D. The part load efficiency is not affected by the flux density.