1. Introduction
The railway transport and rolling stock maintenance sector in Ukraine requires a high level of reliability of automation systems. Modern locomotives, passenger carriages and specialized track equipment are controlled by microprocessor control systems. The basis of these systems are industrial controllers that operate under harsh operating conditions: vibrations up to 5g, temperature amplitude from -40°C to +70°C and constant electromagnetic interference.
In such conditions, the uninterrupted power supply to the non-volatile memory of the controllers is a critical requirement. In this article, we will consider the technical aspects of applying the battery Allen Bradley 1756-BA2 in the railway industry, analyze typical failures, and propose technical maintenance strategies according to the standards ДСТУ EN and ISO.
2. Critical components of the moving equipment control systems
The central element of the architecture of control for many modernized electric locomotives and signaling systems is the Allen-Bradley ControlLogix series controllers. For saving user data and configuration in case of power failure, a lithium battery Allen Bradley 1756-BA2 (3V, 1200 mAh, lithium-thionyl chloride) is used. It ensures the retention of information in the RAM memory of the processor modules and memory according to the standards IEC 61131-2.
In addition to the battery 1756-BA2, the following interrelated components are operating in the locomotive control cabinet:
- Allen Bradley 1756-PA72 — AC/DC power supply module with redundancy.
- Schneider Electric TeSys D — electromagnetic starters for switching circuits of auxiliary drive motors (standards EN 60947-4-1).
- WAGO series 750 — input/output modules for signal collection from coupling sensors and braking systems.
- Phoenix Contact QUINT POWER — power supplies with 24 VDC output voltage and SFB (Selective Fuse Breaking) function.
3. Typical Layout Scheme of Equipment on a Mobile Site
The motion control and diagnostics process is built on a hierarchical principle. Below is a description of the technological flow and locations of critical components:
- Sensor level (field): Inductive wheelset speed sensors, brake main pipe pressure sensors (0-10 bar) and bearing temperature sensors are installed directly on the wheelsets.
- Data collection level: Signals are sent to distributed input/output modules (for example, WAGO 750), located in sealed undercarriage boxes (protection class IP65 according to EN 60529).
- Main control unit: The control cabinet in the locomotive machine room contains a ControlLogix rack with a processor and a battery Allen Bradley 1756-BA2. This unit processes safety signals, controls the traction drive, and transmits data to the driver's control panel via an EtherNet/IP or CANopen bus.
4. Failure Modes and Impact of Downtime on Production
Full or partial failure of the control system due to battery discharge 1756-BA2 causes erasure of the operating program and configuration data in the CPU memory. This results in stopping the locomotive on the track or in the depot.
Технічна примітка: Літієві батареї мають нелінійну криву розряду. Падіння напруги нижче порогового значення 2.0V призводить до миттєвої втрати пам'яті процесора під час циклу перемикання живлення (Cold Boot).
Economic losses from vehicle downtime are very high:
- Cost of unplanned downtime of a mainline electric locomotive on the line: from 1200 € to 3500 € per hour due to disruption of traffic schedules and penalty sanctions by the carriers.
- Costs of evacuating a faulty train with a helper locomotive.
- Risks of emergency situations (safety requirements according to standards ISO 26262 / EN 50126).
5. Maintenance Strategies: Preventive versus Predictive
For railway transport, the traditional approach "failure is removed after the fact" is unacceptable. The modern industry is transitioning to a condition-based maintenance (Condition-Based Maintenance) and preventive maintenance (Preventive Maintenance) strategy according to ISO 13306.
| Comparison Criterion | Reactive Maintenance | Preventive maintenance |
|---|---|---|
| Frequency of replacements | After an emergency failure (unpredictable) | Planned (every 12-24 months) |
| Mean Time to Repair (MTTR) | 8–14 hours (including software reload) | 0.5 hours (hot swap) |
| Compliance with safety standards | Low (deviation from norm EN 50128) | High (full compliance with regulations) |
6. Practical Example: Depot Failure and Its Elimination
During the pre-trip inspection of the freight electric locomotive series VL80 (modernized with installation of Allen-Bradley system), an error code "PLC Battery Low" appeared on the driver's display. Instead of starting the trip, the locomotive was sent to the inspection track to prevent an emergency stop on the mainline.
Work Execution Procedure:
- The electrical mechanics team disconnected the input power supply of the control cabinet (in accordance with the electrical safety requirements DSTU EN 50110-1).
- Thanks to the design of ControlLogix modules, the battery Allen Bradley 1756-BA2 could be replaced while the processor was either powered on or off (depending on the version of the chassis with power redundancy support during replacement).
- The integrity of the program was checked using RSLogix 5000 software.
- The locomotive successfully passed the diagnostic test and was allowed into operation 45 minutes after the fault was detected.
7. Spare Parts Management
To ensure uninterrupted operation of repair enterprises for rolling stock, it is necessary to optimize inventory. Lithium batteries have a limited shelf life due to the natural self-discharge of chemical elements.
- Minimum Safety Stock (Safety Stock): Keep at least 10% of the total number of installed controllers in stock, but no less than 5 units of batteries 1756-BA2.
- Date of manufacture control: Buy batteries only from verified suppliers with origin certificates (CE, UkrSEPRO), since counterfeit power elements lose their capacity within a few months.
- Умови зберігання: Зберігайте літієві елементи при температурі від +15°C до +25°C у сухих приміщеннях згідно з рекомендаціями виробника.
8. Conclusion
Reliability of automation systems in mobile equipment depends on small, seemingly insignificant components, such as lithium-ion memory batteries. Regular audit of equipment condition and usage of original spare parts minimizes the risks of unplanned downtime. For selection and ordering of reliable automation components visit UNITEC-D E-Catalog.
9. Normative References and Sources
- DSSTU EN 50126: Railway Transport. Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS).
- DS TU EN 61131-2: Software Controllers. Part 2. Requirements for Equipment and Testing.
- ISO 13306: Technical Maintenance. Terminology of Technical Maintenance.
- Technical documentation from the manufacturer Rockwell Automation regarding the ControlLogix systems.
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