A transformer transfers electrical energy from one circuit to another through the medium of a magnetic field. The transformer may step up voltage, step it down or deliver energy at the same voltage.

The safety isolating transformer is one of the most widely used of all transformers. It is designed to achieve an accurate voltage ratio within a specific load range.

There is no direct connection between the windings. They are only connected by the intangible lines of magnetic flux in the core. In some types of circuits the transformers may have 1:1 ratio—that is to say no step-up or step-down function. The only reason for this transformer is to isolate the load currents from the supply.

Single Phase Power

Watts = VA x Power Factor (pf)

VA = Secondary Volts x Secondary Amps

Three Phase Power

VA = 1.73 x Secondary Voltsline-line x Secondary Ampsline

Auto transformers

Effective Core Size = VA _actual [1 – (V _minimum ÷ V _maximum )]