Power Transformers - Introduction

A Transformer can be defined as a static electrical device which transfers power from one circuit to another by means of electromagnetic induction. The transfer is accompanied without any change in the frequency.

The term power transformer is generally used to refer to transformers with a rating of 500kVA or greater.

Power transformers are used in distribution systems wherever there is a need to interface between different voltage levels i.e. to step up and step down voltages.

Power transformers are generally of the liquid-immersed type. However, Power transformers used for indoor applications may be air-cooled.

Based on the size ranges, transformers can be classified into three types.

Small Power Transformers : 500 to 7500kVA
Medium power transformers : 7500 to 100MVA
Large power transformers : 100MVA and beyond

The average life of a transformer is around 30 years.