3.0 Transformer Basics
Primary turns, Np
An alternating voltage, Vin applied to the primary creates an alternating current Iin in the primary winding.
The current produces an alternating magnetic flux in the core.
The alternating magnetic flux generates a voltage, Vout, in the secondary
For sine-waves, the flux density, B = Vin / ( 4.44 N A f)
– where N = Number of turns,
– A is the cross sectional area of the core,
– and f is frequency.
Since for a given transformer, B, A and f are constant: -
– Step up or step down ac voltage
– Step up or step down ac current
Because there is no electrical connection between the primary and secondary windings they provide isolation from one electrical circuit to another.
It is these unique properties of transformers that make them so widely used in all kinds of electrical / electronic equipment.