Introductory Electrical Engineering With Math Explained in Accessible Language

12Generators: And Motors

12.1 Introduction

In this chapter, we will examine electric generators that are direct applications of electromagnetic induction and their cousins, electric motors.

12.2 Electric Generators

Electric generators are devices that can generate alternating current (AC) by the movement of a wire winding inside a magnetic field, for example.

Figure 12.1 shows the idea behind a simple generator: a winding of wire that rotates inside a magnetic field generated by two static magnets.

Figure 12.1 Electric generator (winding at 0°).

In real life, windings are attached to an axis that rotates by external force like the turbine of a hydroelectric power plant.

As the winding rotates, its turns of wire cut the magnetic field lines, represented by the arrows in Figure 12.1. This process induces electrical current in the winding.

12.2.1 How It Works

Suppose the winding is, initially, at the position 0°, represented by Figure 12.1. The winding is cutting the magnetic field at a position of minimal induced current. The induced current at this point is 0.

Moved by external forces, the winding rotates anticlockwise and cuts more magnetic field lines. The induced current increases gradually across the winding. When the rotation reaches 90°, as shown in Figure 12.2, current reaches its maximum positive value.

Figure 12.2 Electric generator (winding at 90°).

Rotation ...