Applications
A locomotive is a railway vehicle that exceeds 20 metres in length and weighs up to 200 tons and is designed to haul convoys of goods or passengers. Powerful motors with electric or hybrid drive (diesel-electric) guarantee the traction necessary to tow coaches and the ability to climb slopes while maintaining stable speed. Locomotives are the main elements in a train; many trains have two units, one at the head and one at the tail.
Requirements:
Control of the master controller
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Pneumatic braking system
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Air conditioning system
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Pantograph management
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Stability on curving tracks
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Firefighting system
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Requirement:
Control of the master controller
Control of the Master controller is crucial for driving a locomotive. Traditionally managed with rotary potentiometers, these devices have been replaced by non-contact position sensors, which reduce wear and ensure greater durability. Accuracy and resistance to vibration and environmental conditions are of paramount importance.
Solution:
The GRN sensor can be easily integrated into the throttle through shaftless mounting, which offers freedom of movement and ease of installation. This technology eliminates problems related to mechanical wear and reduces interference, in addition to being suitable for new generation trains and trams.
Requirement:
Pneumatic braking system
Train braking systems rely entirely on pneumatic circuits, which guarantee quick response times and have lower maintenance requirements than hydraulic solutions. The maximum working pressure is typically 16 bar. The safety of the convoy depends on constant and accurate pressure monitoring. In addition, pressure transmitters must be able to withstand harsh environmental conditions, such as high temperatures, vibrations and humidity, and must be compatible with advanced electronic systems, such as ABS and ECP.
Solution:
The KM RAIL pressure sensors, with solenoid valve output, are easily integrated into the pneumatic control panels in the cabin. This configuration ensures continuous monitoring and compatibility with the main rail systems, while EN50155 certification means they are also compliant with safety regulations.
Requirement:
Air conditioning system
In passenger trains, passenger comfort depends on specific HVAC systems. Compared to the systems used in buildings, the pressure of the system is higher, with much broader operating temperature ranges. These systems require accurate pressure and temperature monitoring to ensure effective cooling and ventilation.
Solution:
The Gefran KM RAIL pressure sensor with M12 connector constantly monitors the air pressure in the ducts, detecting variations due to dirty filters, leaks or malfunctions. With its mechanical strength and rapid response, it ensures airflow balancing in real time. The Gefran TR6 temperature sensor accurately measures the thermal value of incoming and outgoing air, providing critical data to the control system to modulate cooling or heating.
Requirement:
Pantograph management
The pantograph must ensure a stable contact with the overhead line so that power can be supplied to the train. Increasing speed increases friction and amplifies the effect of unevenness in the line, making contact less reliable. For this reason, in addition to position control through sensors that adjust the height and width of the pantograph according to the conditions of the line, the speed of the train and external factors, it is also essential to monitor the force exerted on the electrical cable. This ensures continuity in power supply, minimises component wear and ensures optimal safety and performance of the electric drive system.
Solution:
The pantograph management system consists of three components that work synergistically:
- The Gefran RK5 position transducer, with internal cylinder mounting, is designed to withstand shocks and vibrations, while Hyperwave technology ensures reliability and durability.
- The KM RAIL pressure probe with EN50155 certification manages the movement of the pantograph.
- The Gefran TH load cell constantly monitors the contact force of the pantograph with the overhead line: sufficient to ensure continuity of supply but controlled to avoid premature wear of both the pantograph and the railway cable.
Requirement:
Stability on curving tracks
Suspension control on locomotive and coach axles is used to adjust suspension position and pressure according to line conditions, train speed and external stresses, improving passenger comfort, train safety and track and vehicle durability. The anti-tilt system maintains the locomotive and coaches/wagons stable, compensating for tilting on curving parts of the line.
Solution:
Gefran offers the RK-5 and KM RAIL pair of sensors for a complete anti-tilt system: the RK-5 unit detects cylinder positions precisely, while the KM RAIL sensor continuously tracks fluid pressure. The result is a dynamic and coordinated control of the vehicle’s position, translating accurate data into better balance, comfort and operational safety.
- RK-5 is a non-contact magnetostrictive position transducer, designed for internal installation in cylinders.
- KM RAIL is an ultra-compact pressure transducer created specifically for railway applications. Made of stainless steel, it is certified as compliant with RAIL EN 50155, SIL2, PLd; its protection rating is IP69K.
Requirement:
Firefighting system
Fire safety in trains is guaranteed by systems that use inert gases, water mist or aerosols. These systems require continuous monitoring of pressure in the cylinders (which is typically between 42 and 80 bar) to ensure effectiveness in the event of an emergency. Railway regulations require “RAIL” and “fire and smoke” certifications.
Solution:
KM RAIL pressure sensors with M12 connector are certified for railway applications (EN50155) and comply with “fire and smoke” regulations. They are built in a way that minimises the use of plastic materials and that makes them suitable for use in critical environments, ensuring safety and reliability even in emergency conditions.
Operating Principle
A locomotive is not a single machine, but a complex set of subsystems that work in a closely interdependent manner. The heart is the drive unit: in electric models, energy comes from the overhead line via the pantograph, while in diesel-electric versions, a diesel engine powers a generator that produces current for the drive motors. In both cases, power is transferred to the axes, transforming energy into motion.
Complementing functions, essential for reliability and safety, are linked to this core. The braking systems (almost always pneumatic) guarantee rapid and controlled decelerations, taking advantage of the compressed air distributed throughout the entire convoy. To maintain a stable power supply, the pantograph must always touch the overhead line, and this contact is regulated by pressure and application force. In passenger trains, comfort depends on air conditioning systems that maintain optimal temperature and pressure inside the coaches.
Each subsystem communicates with the others: the delivered power influences braking; the stability of the suspensions affects the efficiency of the pantograph, while fire safety systems protect vital compartments. A locomotive is therefore a machine-system, where mechanical robustness, pneumatic control and advanced electronics intertwine to transform hundreds of tons of steel into a vehicle that can move huge loads with precision and continuity.
Requirements and Technology
A locomotive has different requirements that reflect the nature of its subsystems. Each of them plays a specific role, but they all contribute to ensuring traction, safety and continuity of service.
- Master Controller: The driver’s main command requires precise and resistant position sensors, which can translate a human gesture into stable power regulation.
- Brake system: Safety relies on pneumatic networks that work at pressures up to 16 bar; every pressure variation must be monitored with the utmost reliability.
- Air conditioning in coaches: Here the priority is comfort: pressure and temperature must remain under constant control, with components already validated by the manufacturers of railway HVAC systems.
- Pantograph: In addition to pneumatically powered rising and lowering movement, the contact force with the overhead line must be measured so as to ensure continuous power supply without excessive wear.
- Suspensions and stability (anti-tilt): During curves and stresses, it is essential to compensate for inclination to ensure comfort and reduce structural stress, by combining position and pressure sensors.
- Fire-fighting systems: Last but not least, the monitoring of inert gas cylinders or water mist requires certified transducers, which must be compliant with RAIL and “fire and smoke” regulations.
Viewed together, these requirements show how a locomotive is a technological mosaic, a balance of mechanics, pneumatics and electronics, where each subsystem supports the other. Gefran offers a complete range of pressure and position sensors, easily integrated into any system, to ensure efficiency and safety on locomotives.
