Cathodic protection rectifier

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Cathodic protection rectifiers are AC-powered electrical equipment that provide direct current for impressed current cathodic protection systems.[1]

Typical cathodic protection rectifier with transformer tap voltage selection bars at the top of the front panel.
Simple cathodic protection diagram

Rectifier units are often custom manufactured and equipped with a variety of features, including oil cooling, automatic output adjustment, various type of electrical enclosures, remote monitoring, remote output adjustment, an AC electrical outlet, selectable AC input setting, three phase AC input.


Cable connections

The rectifier output DC negative terminal is connected to the structure to be protected by the cathodic protection system.[2] The rectifier output DC positive cable is connected to the auxiliary anodes. The AC power cables are connected to the rectifier input AC cable terminals.

Output adjustment

The output of the rectifier is usually determined by a cathodic protection expert to optimize the level of protection on the target structure. Many rectifiers are designed with taps on the transformer windings and jumper terminals for connection of jumper bars. The jumper bars or tap bars are moved among taps to vary the voltage output of the rectifier unit.

Rectifiers for water tanks and used in other applications are made with solid state circuits to automatically adjust the operating voltage to maintain a target current output or structure-to-electrolyte potential.[3]


Analog or digital meters are often installed to show the operating voltage (DC and sometime AC) and current output. Typically a shunt circuit composed of a calibrated resistor and voltmeter is used for current output measurement.

Power sources

Most CP rectifiers are supplied power from the electrical grid and in locations far from AC power lines, alternate sources of power are used. These include solar panels, thermoelectric generator or, for small output systems or rectifier units for current requirement testing, batteries are used.[4]


  1. ^ Peabody p.157
  2. ^ Peabody p.158
  3. ^ Baeckmann, Schwenck & Prinz, p.233
  4. ^ Baeckmann, Schwenck & Prinz, p.225