Question

1- How do you evaluate the power

factor of the transformers when lightly loaded? And why?

2- How can eddy current loss be reduced?

3- How can hysteresis loss be reduced?

4- How can copper loss be reduced?

5- What are the main methods to control transformer noise?

Answer 1

1. The power factor is the most important term associated with transformer. The power factor is defined as the ratio of real power to the absorbed power. During a lightly loaded condition of transformer there is a risk that over compensation may occur therefore the power factor needs to be monitored regularly during the light load condition of transformer. By calculating the amount of of reactive power absorbed by the transformer we can calculate the power factor.

2. There are various types of losses occurring in a transformer. Such losses can be suppressed by various techniques. The Eddy current loss can be reduced if the resistance of the core is increased. We know that in a transformer the core is made up of lamination of Steel sheets therefore if the laminations are thin then the core of a transformer will have high resistance.

3. The hysteresis loss is a loss in transformer in which the energy is dissipated in the form of heat. This heat is produced by work of magnetising force against the internal friction of the machine. This loss can be reduced if a material having least hysteresis loop area is used. Since Steel has very less hysteresis loop area therefore is widely used in construction of transformers.

4. The copper loss is generated in a transformer due to the DC resistance of the machine. To minimise the copper losses in transformer the windings of Transformers are made thick .

5. Noise in a transformer is another factor which needs to be controlled. Various sound damping materials are employed in transformer to damp the noises emanating from it. The main cause behind large noise generation in a transformer is the magnetostriction effect. Various acoustic damping material, oil barriers, cushion padding are used to reduce the noise from a transformer.