Introductory Electrical Engineering With Math Explained in Accessible Language

11Transformers: Not the Movie

11.1 Introduction

In this chapter, we will examine transformers, components created by combining inductors.

11.1.1 Transformers

Inductors have this name because they induce current into other elements.

Suppose we have a coil inside another one, like shown in Figure 11.1.

Figure 11.1 Two coils, one inside the other.

Both coils are electrically insulated from each other and we apply an alternating current to the first one. This first coil will develop a variable magnetic field, and because the other coil is closer, the second one will absorb part of this magnetic field and produce a variable current. In other words, without any electrical contact, the first coil produced or induced a current on the second one.

A new component was born: the transformer.

In a transformer, the first and the second coils are normally called primary and secondary windings.

11.2 Connected by the Magnetic Field

There is no electrical connection between the primary and secondary coils. However, they are connected by the magnetic field, and they will work by mutual influence.

Like we have explained before, the magnetic field developed on the primary will induce a current in the secondary. Consequently, this secondary current will produce a magnetic field in the secondary, which will induce current on the primary and so on, ad infinitum.

The primary and the secondary ...