Basic Rectifier Circuits

If the terms e and E_m are changed to i and I_m, then the equation for the rectified current results.

The first term is the desired rectified direct-current component c; the second term is a component d having the same frequency as the source; the third term is a second harmonic e having a frequency twice that of the source; and the fourth term is a fourth harmonic f having a frequency four times that of the source. These separate components are plotted in Fig. 9, and, if they are combined, as by adding at the broken lines, Fig. 9(b) results.

Full-Wave Rectifier. A sine-wave voltage a will produce a full wave such as shown by b of Fig. 10. The equation for the rectified full-wave voltage across the load is

This equation can also be used to represent the rectified current. The first term is the desired rectified direct-current component. The other terms are the second, fourth, and sixth harmonics; other harmonics are neglected. These components can be represented in the same manner as in Fig. 9 and then can be combined to give the wave of Fig. 10(b). Polyphase Rectifiers. When a large amount of power, perhaps a kilowatt or more, is to be rectified, polyphase rectifiers are used.

Figure 10. A full-wave rectifier. The impressed voltage is shown at a, and the rectified current and voltage at b.

Three-phase rectifiers are often used with large radio transmitters,⁸ and rectifiers of greater numbers of phases are commonly used in large industrial installations.⁹

Bridge Rectifiers, A full-wave bridge rectifier is shown in Fig. 11. For either direction of the applied alternating voltage, current will flow through the resistor as shown. The transformer may be omitted if desired.