Multi-Section Digital Axle Counter MSDAC-730P

MSDAC-730P is a multi section digital axle counter system that is designed using the principles of fail-safety and has a two-out-of-three fail safe architecture. It is microcontroller based and has redundant power supply arrangement. Its modular nature allows you to plan your upgrade and extensions without any problem. It is extensible with 8 detections points in a module set. It provides an easy to use GUI for configuration. 

It is used for detecting railway track occupancy primarily in a station. It is used for track circuiting a whole station. MSDAC-730P is modular in design and can be used with 40 detection points per chassis. Each detection point has a track sensor that identifies a track section boundary. A track section can be defined with 2/3/4 detection points. 

The system consists of the following components:

  1. Axle Detectors
  2. Electronics Field Units
  3. Central Evaluator
  4. SM's Reset Panel
  5. Monitoring Unit

The Central Evaluator of MSDAC-730P has been designed to be modular. The system can be configured for up to 40 field units in steps of 8.  Therefore, the system has the provision to scale up or scale down according to the requirement at station.

The Axle Detectors are installed at the limits of a track section along with their electronic field units on track side. The number of detection points is decided based on the tracj circuiting requirement of a station. The field units are connected with Central Evaluator by means of ½ Quad cable. The Central Evaluator is installed at the station and is powered by 24V DC local supply. The field uits are also powered using 24V DC that is dereived from the power source that powers the central evaluator. The Axle Detectors operates on high frequency (21 KHz & 23 KHz) electromagnetic wheel detection technology. When a train wheel passes over the Axle detectors, the change in electromagnetic field is sensed. This change triggers a complex algorithm that decides if a wheel has passed over the axle detector. The Axle detectors and the electronics associated with it is working on the principle of Phase Modulation.

The wheel-detection events are converted into pulses and these pulses are counted by the field units. These countsa re stored as well here. The stored counts as well as the healt of the track sensor are monitored and are continuously transmitted bynthe field unit by means of telegram packets to Central Evaluator on the ½ Quad cable that also powers the field unit. The central Evaluator receives the count from each of the field unit it is connected to and it then takes the decision of the track section is occupied or not. This decision is taken based on 2003 voting logic in a fail safe manner. MSDAC signals the occupancy of the track section by means of an electro-mechanical relay called VR relay. The contacts of VR is used in the signaling circuits of signalling system at the station.

MSDAC has a mechanism to reset a particular track section to recover from an error or a failure condition. This is done through the SM's reset panel. The section is to be physically verified by the SM to be unoccupied and then the reset command is to be given from the reset panel. This command is received by the central evaluator and it then send the command to the respective field units to zero their counts.

It is designed in accordance with the RDSO specification No. Specification No. RDSO/SPN/176/2005 to meet CENELEC SIL-4 standard.