Hind Rectifiers Limited
An ISO:9001:2008 Company
Cathodic Protection Transformer Rectifier

Cathodic Protection Transformer Rectifier

Cathodic Protection Transformer Rectifier

HIRECT make Cathodic Protection Transformer Rectifier unit (TRUs) comprise of Automatic, Manual & CVCC controlled. CP-TRU is used for cathodic protection of buried pipelines across the country,storage tanks at terminals /refineries and other buried structures.


TRUs are used to prevent submerged (Soil or water) metallic structures from corrosion. All submerged Pipelines (Oil, water etc.), concrete structure of bridges/ buildings / sea ports etc can be protected from corrosion by doing CP.

TRUs impress DC Currents in to the Carbon-steel/steel structure to be protected in opposite direction to the galvanic corrosion currents & protects the structure from corrosion.

To obtain the optimum level of protection under varying conditions, it is necessary to vary the impressed current continuously so as to maintain a constant level of protective potential at the structure. This continuous monitoring and control can be achieved by providing an automatic control for the cathodic protection system.

HIRECT offers several types of TRU which are designed, manufactured and tested under strict quality assurance system to achieve highest quality standards.


All the Transformers used in TRUs are designed to give high efficiency with low loss. The coils are wound with high conductivity, annealed, insulated electrolytic copper and core material is high permeability, low loss CRGO/CRNGO. The insulation material used is of high standard Class F. Designed and tested as per IEC 76/IS 2026 standards.


Rectifiers are based on internal quality standards and our own make Diodes / Silicon Controlled Rectifiers. Rectifier circuits have different topology depending upon the load requirements.

Designed and tested as per IEC146/IS 3136 standards.

Modes of Operation

Auto Reference Mode

The operation of the TRUs in this mode will be fully Automatic and will be controlled by reference electrode feedback.The unit will automatically maintain reference voltage or P.S.P. within ± 15 mv of the set value under all conditions.

Manual Mode

The DC output voltage of TRU will be controlled in 24 symmetrical steps by means of a separate Autotransformer with Coarse & Fine tapping.


The unit will be operated in Constant Voltage or Constant Current mode.

In constant voltage mode the DC output voltage will be settable from 0 to rated value in stepless manner by means of voltage adjustable pot.

In constant current mode the DC output current will be settable from 0 to rated value in stepless manner by means of current adjustable pot.

Features and Benefits

Types Of Unit Natural/Forced Air Cooled, Oil Cooled | Indoor or Outdoor type.
Control Element The DC Output will be controlled through latest solid state Silicon Controlled Rectifiers (SCRs) with plug in type control card of electronic circuits.
AC Inputs Single phase or three phase, 50 Hz/ 60 Hz
DC Outputs DC output Voltage - Upto 200V
DC output Current - Upto 500A
Meters 48 x 96 mm, 3 ½ Digit Digital meters as under
  • Input Voltage:0 to 750 V AC
  • Input current:Ammeter with suitable CTs
  • Output Voltage :As per output rating
  • Output Current:Ammeter with suitable shunt
  • PS.P: 0 to ± 19.99 V DC
Indications Mains ON , Auto Mode , Manual Mode , Auto Ref. mode , CVCC mode , under protection, Over protection , All Ref. Fail , Current Limit.
Protection Normally we provide following protections
  • MCBs with HRC Fuses in AC Input & DC Output
  • Over current limit & short circuit protection through electronic controller
  • Glass cartridge fuses in the all auxiliary power lines to control circuit
Operational Climatic condition TRUs are designed to work under severe environmental conditions with ambient temperature of 50 ° C and humidity of 95 % (non condensing). Enclosure confirming to class IP 55 degree of protection.
Enclosures Enclosures are fabricated from 2.5 mm/2.0mm/1.5 mm CRCA sheet and confirming to IP55 degree of protection. Stainless Steel Cabinets for corrosive atmosphere. Lockable doors shall be provided in the Front and Back. Polycarbonate window is provided viewing meters and indications.
Finish Powder coating /Paint of required shade and thickness with proper treatment to suit corrosive/site conditions.

Additional Features

Following additional features can be provided as per Specifications along with Rectifiers

Interrupter Timer

The Interrupter timer is used for carrying out ON/OFF CP survey using the current interruption technique.

  • Stand Alone Interrupter Timer
  • GPS synchronizable Interrupter Timer

SCADA Monitoring Facility

Isolated 4- 20 m A are provided for DC output voltage, DC output current and pipe to soil potential (PSP)

Remote Monitoring through GSM Data Logger

The parameters values can be remotely monitored using the GSM based remote monitoring systems

Multichannel TRU as per requirements

Optimizing space and size of the TRU for varied outputs.