Earth Return Current Units – Ground brush

The first function is to prevent the passage of current through the axle boxes (bearings).

The flow of electric current through the axle box roller bearing of railway vehicles is one major problems for the safety and reliability of rolling stock.

It is necessary to use devices shunting the greatest part of the current through the axles and wheels without flowing through the roller bearings.

The second function is to insure rails equipotentiality.

The third function is to Transmit Trains signal detection between 2 rails portions for each districts.

An additional function can be integrated in the ERCU is the pulse generation with a dented wheel.

Uses of ERCU Ground brush

The benefit of using the ERCU from Mersen is to benefit of the design of the company which have created this device using its own impregnated graphite brushes.

Mersen strongly recommend to use Mersen carbon brushes, specially designed for ground brushes Mersen.

Mersen recommends to use Mersen brushes, specially designed for Mersen ERCU.

Brushes are made of an agglomerated mix of copper and graphite powders. The copper percentage is high in the to give a low electrical resistance and the ability to the brushes to carry up to  25 A/ cm², without any damage for the contact disc.

Contact discs are made in a special bronze.

ERCU performances are obtained only with this type of brush.

Configuration

Three configurations are possible depending of the application (Train, Tramway or Metro)

• Axial or axel end for trains and Metro
• Radial or top for trains and Metro and
• Into the wheel for low floor tramways

Current range

Depending of the number and the size of the impregnated carbon brushes, the ERCU range covers from 200 to 800 Amp with ERCU equipped with 1 to 4 brushes (12,5x32; 16x25; 20x25; 20x40; 25x50mm).

Short time withstand current

• Short time withstand current 100ms can go up-to 7kAmp
• Short time peak withstand current can go up-to 19kAmp.

IP protection

The range offers IP 547 as basic protection but adding some gaskets, some ERCU can offer IP56.

Material used

• Material of body = Stainless Bronze, connection tinned
• Material of cover = 3 mm thick zinc plated (15 microns) steel cover plate, Aluminium Alloy,
• Brass or Stainless steel
• Material of spring and screws = stainless steel
• Material of insulating ring = Compound polyester 

Pulse generator or speed sensor

An angular speed sensor is mounted on the ERCU and transmits to an electronic system that can:

• Detect when a wheel slips to control traction or engine speed, or to trigger an anti-skid system.
• Detect whether the train is running or stopped, in order to trip or release safety systems such as door locks.
• Detect which way the train is traveling.

Mersen do not provide the sensor itself but prepare a space to install it.

Cable connections

Connexion plate can be designed for “external” or “internal” connexions to
meet your requirements. Also the cover of the ERCU can be electrically isolated.

Painted cover

Mersen can supply the covers painted in relation with the colour of the train.

Cataphoresis protection

Mersen offers a cataphoresis coating of the cover for a protection to 1000h to salty mist test.

Slip discs

The slip disc is the component fixed on the wheel on which the brushes are in contact to pass the current.

Identification

Each ERCU is identified with a lot number but Mersen can also add QR code.

Tooling

Beside the spare parts, Mersen can supply the necessary tooling to set perfectly your equipment to the technical requirements of your network and optimize their use.

LCC; RAMS; Type tests

Mersen team provide type test and different studies (Life Cycle Cost, RAMS, FMEA, Eco Design and recyclability, etc…) to secure the reliability of your equipment and its conformity to standards and legislations.