Railway Resistive and Inductive Elements

Power Resistors in Railway Vehicles

Consuming the excess energy is the main motive to use resistors in power train circuit of a rail vehicle. Either of braking effort without mechanical wear or preventing the power electronics converter switches from highly damageable excessive over voltages, or both; power resistors have a wide range of utilization area in rail vehicles.


The physical conditions inherent to railways; enforce power resistors to be more robust, rugged and reliable than the conventional resistors utilized in industry. EN 60322 is the main standard for railway dynamic brake resistors, defining the technical design and test challenges specific to railway operational conditions. There are also other standards relating to vibration, insulation, and etc., which specifically address the railway conditions referred in EN 60322.

Rail vehicle type is the main decisive factor in the design and test guideline of power resistors utilized in rail vehicles. The primary reason for the power resistors being vehicle dependent is the fact that the rail vehicles are designed in a customized vehicle concept with regards to propulsion power, total passenger count, and operational speed limits. Therefore, the resistor requirements of each vehicle type usually differ from each other.

Most of the modern rail vehicles are equipped with the propulsion power electronics having ability to feed the braking energy back to catenary. In mass transit networks like metros and tramways; catenary power supplies do not have sinking ability to intercept regenerative energy and transfer it to the grid due to the one-quadrant operation capable diode based power electronics circuit structure. Braking the rail vehicle through power resistors is the safe way for the vehicles used in light duty rail transport like metros and tramways.

In contrast to the public transport railway networks; main line railway networks like intercity passenger transport or heavy freight logistics usually have catenaries having ability to provide energy flow from grid to trains, or vice versa. Concerning the mainline railway vehicles; power resistors are mainly used in diesel-electric locomotives. Also the electric locomotives which do not have bidirectional energy flow ability must use power resistors to utilize regenerative braking.


Standards for Railway Resistor Applications


  • IEC 60322 : 2001 Railway applications - Electric equipment for rolling stock - Rules for power resistors of open construction.
  • IEC 61373 : 2010 Railway applications - Rolling stock equipment - Shock and vibration tests.
  • EN 50124-1 : 2001 Railway applications. Insulation coordination. Basic requirements. Clearances and creepage distances for all electrical and electronic equipment.


Dynamic Braking Resistors in Public Transport Rail Vehicles


The rail vehicles used in public transport networks are operated in an accelerate/decelerate drive cycles between stations. The propulsion energy flow is from the catenary to traction motors and then from traction motors to converter side. Direction of energy flow periodically changes between the stations. In a service life of a metro or tramway vehicle; public transport rail vehicles have thousands, maybe millions times of acceleration and deceleration phases. So, it is very critical to use regenerative braking through deceleration phase in order to extend the life span of mechanical brakes. Power resistors are the key components for regenerative braking to be successfully applied under all conditions of catenary voltages. Also the dynamic braking resistor has lower wear and tear than the friction braking.



The braking resistors are designed according to braking power, braking time, isolation requirements, mounting place, and cooling method. The railway braking resistors could be located on the vehicle roof, under the vehicle or in special compartments. The air natural cooling or forced air cooling methods could be used for cooling down the braking resistors.


Features of Power Resistors Utilized in Public Transport


  • Negligible ohmic value change in case of sudden temperature rise of resistive elements
  • Highly robust mechanical structure against vibrations
  • Long life against thermal cycling due to the accelerate/decelerate phases


Dynamic Braking Power Resistors in Heavy Rail Vehicles

Braking is not a periodically changing event in heavy rail vehicles. Acceleration and deceleration is highly dependent on the slope of the railway. Freight locomotives may carry up thousands of tonnes of loads from seaports to the hills or may carry down huge amount of freights from hills to the seaports. So the braking resistors are key components for the mechanical brakes not getting immediately worn out. The braking resistors may have continuous braking profile for long durations. Power resistors used in heavy rail vehicles must show highly robust mechanical structure at high temperatures. Also not to degrade the braking power of locomotives while the resistors are getting hot, it is crucial that resistance change should be kept minimal in temperature rises.



Features of Power Resistors Utilized in Heavy Rail Vehicles


  • Negligible ohmic value change in case of sudden temperature rise of resistive elements
  • Continuous operation at high temperatures
  • Highly robust mechanical structure against vibrations


Crowbar Resistors, Heaters


The main idea for the crowbar resistors is to protect the traction converter power electronics switches from highly damageable excessive over voltages. There are two types of crowbars.

1. Soft Crowbar : Soft crowbar is utilized to reduce the DC link voltage in case of DC link overvoltages. Soft crowbar resistor is connected to DC link with a serial connected IGBT.

2. Hard Crowbar : Hard crowbar is utilized to force the high speed circuit breaker getting open in order to protect whole converter parts from massive damage caused by overvoltages. Hard crowbar resistor is always connected to DC Link with a serial connected thyristor.

Crowbar resistors are designed to dissipate high energy in a very short time periods. While sizing the electrical ratings of crowbar resistors; input frontend converter component ratings, HSCB rating, the energy stored in DC link capacitance should be taken into calculations



Features of Crowbar Resistors Utilized in Traction Converters


  • Very compact mechanical structure
  • Highly reliable mechanical structure against sudden temperature variations
  • Highly robust mechanical structure against vibrations
  • Negligible ohmic value change in case of sudden temperature rise of resistive elements


Wagon Heater Resistors


Wagon heating resistors are employed either in regenerative braking path or standalone on public rail transport vehicles. Wagon heating resistors are not only resistors as they include double protection devices and diagnosing capabilities.


Protections Used in Heating Resistors


  • Overheating protection of heater elements
  • Excessive heating of wagons
  • Protection against fan faults
  • Protection against power supply faults of sensor supplies
  • Redundant circuit breaker against contactor failure
  • Both switching on/off the heating resistors state signals are transmitted to train control system

Hilkar wagon heating resistor solutions are designed and manufactured in the scope of EN 60322 Standard. Sub-components used inside the heating resistors comply with EN50155 Railway Standard.


Locomotive Testing & Trackside Resistors


Hilkar designs and manufactures custom design load banks for testing of Diesel Electric Locomotives. Power train of diesel electric locomotives consist high power rated diesel engine, an alternator and rectifier units. Testing units are usually connected to DC part of the diesel electric power trains. This is to test both the diesel engine, alternators and rectifier units before commissioning the locomotives.

Hilkar can provide customization either in mechanical or electrical design concepts. Both continuous rated power and pulsating peak power inputs coming from diesel electric power train are perfectly dissipated with well structured thermal design of testing units


Features of locomotive testing units are:


  • Customizable mechanic structure and packaging
  • Ability to cool MWs of dissipated power
  • Customer oriented solutions for the control of testing units
  • Negligible ohmic value change in case of sudden temperature rise of resistive elements


Trackside resistor units are employed in public transport catenary supply grids. The voltage range of catenary supplies are defined in EN 50163 Standard. Traction converters of metro, tramway vehicles are designed in accordance with the maximum allowable catenary voltages defined in this standard


Since the traction power supply of 750Vdc or 1500Vdc catenary public transport grids are diode based converters, their DC side voltages are not controllable. So, there should be some units to limit catenary voltages in order to run the rail vehicles safely. Trackside resistors are the voltage limiters in the case of catenary supply over voltages.



Inductive Components for Rail Vehicles


Inductive components are the critical components for both of auxiliary converters and main drive power electronics systems. Inductive elements for on board AC and DC drive systems must have rugged mechanical structure against vibration and a state of art thermal design in order to have the most compact size.


Air Core / Iron Core Chokes – Reactors


In order to filter out the harmonic components of the catenary supply of converters, line chokes are used. For air core reactors, inductance is kept constant to filter out harmonics during short circuit instances.

Sine filter inductive components; customized for inverters; are usually employed in order to supply traction motors with low harmonic sinusoids.


Transformers for Auxiliary Converters


Transformers at the output stage of auxiliary converters usually supply accessory loads and power supply of electronic circuits. Transformers for auxiliary converters usually require very compact design with well thermal responses in case of full load operation in steady state.




EN 61373 for vibration tests; IEC 60310 for the general standards of railway related inductive components.


Fire Protection Standard EN 45545


Dedicated to serving our customers with customized solutions for on board equipments of rail vehicles such as fire/smoke protection standard EN 45545. Hilkar has a broad range of inductive products ensuring EN 45545 both in air core and iron core reactors/transformers.