The Copper-Oxide Rectifier

Author: E.E. Kimberly

Some minerals and combinations of minerals and oxides demonstrate valve action when placed in an electric circuit. An outstanding example of this phenomenon is that of copper and its red oxide. A copper disc coated on one side with a thin layer of cuprous oxide exhibits a much higher electrical resistance when a current is passed through it in a direction from copper to oxide than when the direction is from oxide to copper.

Commercial rectifiers employing this principle may be bought complete or may be built up of the oxide-coated discs to suit a definite purpose. See Fig. 27-41. Contact is made on the bare side of the copper disc and also on the oxide-coated side by lead or foil washers in the tightly-bolted stack.

Fig. 27-41. Copper-Oxide Rectifier (Note the heat-radiating fins)

Figs. 27-42 and 27-43 show typical circuits and arrangements of parts for copper-oxide rectifiers. Such rectifiers are widely used in radio receivers; in small battery chargers; in rectifier-type instruments; and in many other services, such as in electroplating, industrial truck-battery charging, electrolysis prevention, welder controls, airplane-engine starting, motion-picture projection arcs, "quick-chargers" for batteries, and other high-current loads. Generally speaking, this rectifier is competitive with motor-generator sets up to 12 volts at any current. Above 12 volts the choice of a rectifier would depend on other factors, such as reliability, freedom from moving parts, negligible amount of maintenance required, and ease of control from the a-c side.

Fig. 27-42. Circuit Diagram of Fig. 27-41

Fig. 27-43. Circuit of Full-Wave Copper-Oxide Rectifier