Electrical Engineering ⇒ Topic : Copper Oxide Rectifiers

Copper Oxide Rectifiers

Copper oxide rectifiers are made from copper discs which are usually 25 mm in diameter or smaller. These discs are heated to form a copper oxide on their surface. After the heat treatment they are quenched and the oxide film is removed from one side. The remaining oxide film provides rectifying action. Contact is made to the film through the copper on which it is formed and a lead disc pressed on to the upper surface Fig.(a). The rectifier thus formed will permit a current flow from the film to the copper and will block currents from flowing in the opposite direction. This device is not a perfect rectifier

                                                                      Fig.(a) Elements of the copper oxide rectifier

• This type of rectifier is usually designed to operate at 45°C or less. The voltage impressed on each cell is usually limited to a range of 5 to 11 volts, depending on whether the rectifier is used on continuous or intermittent duty.
• The efficiency of the copper oxide rectifier seldom exceeds 65% to 75%. This indicates a voltage regulation ranging between 25% and 35%.
• This rectifier is not stable during early life. The resistance in the forward direction tends to increase with use at a rate dependent on temperature of operation and its load. Theover-all change of about 15% can be expected in the output voltage. The change is gradual and may continue for a period of several years. This feature must be taken into consideration in adapting it to its circuits.
• The copper-oxide rectifier, because of low efficiency, is unsuitable for rectifying large amounts of power.
• This type of rectifier finds use in control circuits and is adaptable to various voltages and currents.