# Blog

## How do you calculate the capacity of an autotransformer? ## What is the theory of auto transformer?

• Theory of Auto Transformer. In Auto Transformer, one single winding is used as primary winding as well as secondary winding. But in two windings transformer two different windings are used for primary and secondary purpose. A diagram of auto transformer is shown below. The winding AB of total turns N1 is considered as primary winding.

## What is the formula for power transformation in a transformer?

• Power transformation formula: The total power S (Con-VA) in VA is conducted from the autotransformer is equal to the transformation ratio times of the product of the secondary voltage and secondary current. S (Con-VA) = k x V 2 x I 2 At the same time,

## How to find the unknown value of the auto transformer?

• Transformation ratio = primary input voltage / secondary output voltage = Primary current /secondary current = Secondary turns / primary turns Also using above formula you can find the unknown value of the auto transformer.  