Rectifier

A rectifier is the DC power source commonly used in impressed current cathodic protection systems.

Quick Definition

A CP rectifier converts AC power to DC power so current can be discharged from anodes to protect a metallic structure.

Why This Term Matters

Rectifiers provide adjustable current output for impressed current CP systems. Their voltage and amperage readings are important operating data, but they do not prove adequate protection by themselves.

A rectifier must be connected with correct polarity. Reversed polarity can cause severe corrosion of the intended protected structure.

Core Concept

DC output

The rectifier produces DC voltage and current. The positive terminal is normally connected to the anode system, and the negative terminal is connected to the protected structure.

Output adjustment

Rectifier output may be adjusted using taps, controls, or other output settings. Adjustments should be based on field measurements.

Inspection

Rectifier inspection commonly includes voltage, amperage, AC power, fuses, breakers, wiring, cabinet condition, tap settings, and RMU condition if present.

Troubleshooting

Output trends can indicate problems. High voltage with low current may suggest high resistance or an open circuit. Low voltage with high current may suggest a short or increased current demand.

Common Mistakes

  1. Assuming rectifier output proves protection.
    Why it is wrong: Output does not prove current distribution or criterion compliance.
  2. Ignoring polarity.
    Why it is wrong: Reversed polarity can damage the protected structure.
  3. Increasing output without checking interference.
    Why it is wrong: Higher current output can affect nearby structures.

Field Example

A rectifier is found operating at 20 volts and 8 amps. That confirms DC output, but the technician still needs structure-to-electrolyte potentials and current distribution data to evaluate whether the structure is protected.

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