Traction Transformers – "Tractronic®"

Designing and manufacturing traction transformers for rail operators and train manufacturers worldwide, Siemens produces TT transformers that

increase train efficiency and performance - handle highest ratings in a minimum of available space - serve local content demands for worldwide application - afford maximum reliability and flexibility.

Find out how Tractronic Thinity transformers will boost your railway operation

Download info package

Compliance statement

Siemens Energy complies with the laws and regulations affecting traction transformers

Siemens Energy is closely monitoring the development of transformer regulations worldwide e.g. European Eco Design Directive and US DOE rules. Siemens Energy adheres to the rules and regulations communicated e.g. in US and Europe and complies with all relevant requirements for every transformer product delivered. As a trustful and responsible partner Siemens Energy understands the importance of these regulations and will continue to monitor potential future requirements. We will continue to adapt and comply with all relevant regulatory changes.
Areas of application

Turning energy into speed

On-board traction transformers transform energy into speed that moves passengers and freight. As a part of the traction chain, they are crucial to the performance of train and operator services. Siemens designs and builds traction transformers in 5 specification profiles.    

Traction transformers for every application

The perfect transformer for every vehicle

With over a century of experience in transformer technology, Siemens is one of the world’s leading suppliers for customized, state-of-the-art railway transformers. The secret to Siemens stellar track record is a refined system of global logistics, internationally binding quality standards, highly trained skilled workers and specialization.

Compact, light and efficient

Siemens develops and produces traction transformers for rolling stock applications of all relevant ratings and voltage levels. The focus is on maximum reliability, economic efficiency and safety – and ensuring that the transformers are perfectly in line with the customer’s requirements.


Design options

  • power ratings – frequency, capacity and voltage
  • size, weight and place of installation
  • dissipation and short-circuit voltages
  • losses and impedance voltage characteristics
  • driving patterns and medium-frequency performance
  • materials and technologies to meet environmental requirements (e.g. ester coolant)    


Leveraging data for maximum transformer performance

Siemens Transformers offers the opportunity to track the transformers in operation. Operators can not only monitor but optimize transformer performance. Monitoring and data analysis are the important factors for digitalization of traction transformer for rollingstock applications.


A new generation of sensors monitors transformer health

A modular multisensory system continuously monitors the “health” status of the transformer and modifies operation behavior according to the results of an onboard optimization algorithm. The Siemens monitoring system leverages a new generation of sensors. These sensors transmit data to a local, remote or cloud-based control system. After data processing, the actors will – if necessary – receive commands for correcting the operation behavior.


Benefit from the performance data of other traction transformers

Economical and technical information of each traction transformer is updated online and collected to optimize all similar transformers in operation. Our real-time monitoring system optimizes cost of operation cost and maintenance intervals, increasing energy and economic efficiency.


Rely on Siemens Transformers – anywhere, anytime

Siemens traction transformers operates a worldwide manufacturing and service network to serve customers all over the world. Their more than 20 manufacturing sites worldwide adhere to European quality and sustainability standards – regardless of the manufacturing location.


The top 3 customer benefits of Siemens strong global presence

timely responses to inquiries,

short processing time on spare parts orders,

fast access to services directly on-site.


This ensures that customers can rely on Siemens traction transformer, components and services, anywhere, anytime.


Developed, tested and certified

Siemens traction transformers are setting standards of quality and versatility around the world. Close cooperations with international standards committees guarantee the compliance with the specific requirements and standards.


Siemens is a founding member of the IRIS Initiative, and consistently implements its requirements. Our railway components comply with all the relevant standards, for example: DIN, EN, IEC, IEEE, ISO, EAC / GOST and ANSI, as well as the current fire protection standard EN 45545. With our certified components, we actively support the worldwide vehicle approval process; hence our traction transformers comply with all relevant standards, for example:


  • DIN EN ISO 9001
  • DIN EN ISO 14001
  • OHSAS 18001
  • EN 15085-2 CL 1
  • GOST
  • IRIS


Covering every preference

Siemens traction transformers owe their excellent track record to a refined system of global logistics, internationally binding quality standards, highly trained skilled workers and specialization in five basic transformer specification profiles.

Tests for maximum reliability and customer satisfaction

Siemens uses the most advanced and comprehensive routine tests, type evaluations and special tests for maximized product reliability and customer satisfaction. Siemens traction transformers are tested essentially in the same way as power transformers to ensure maximum safety and quality.

  • Measurement of winding resistances
  • Measurement of ratios and proof of polarity
  • Measurement of idling dissipation and idling current
  • Measurement of relative short-circuit voltage,
  • short-circuit dissipation and total dissipation
  • Testing with applied power-frequency withstand
  • voltage (testing of winding)
  • Testing with induced power-frequency withstand
  • voltage (testing of winding)
  • Testing of step switch/tap changer (if present)
  • Inductance measurement on a case-by-case basis

Type evaluations examine different transformer properties, normally these are measurements of heating and lightning impulse voltage testing. For measurement of heating, losses are fed in based on the preceding measurement and subsequent types of operation. In the process, differing oil temperatures and the coolant temperatures (i.e. air/water) are recorded. The winding temperature is determined indirectly based on winding resistance. It measured after the feed-in has been terminated. Pressure and throughflow measurements within the cooling circuit can also be subject of an evaluation. In transformers fed straight from the overhead lines, the high-voltage winding undergoes a lightning impulse voltage test.

  • Measurement of magnetic field strength at different
  • distances from the tank wall in three orthogonal directions
  • Noise measurements
  • Partial discharge measurement
  • Mathematical proof of sudden short-circuit resistance.
  • Upon request, tests may be performed at an accredited third-party laboratory.
Downloads and Support

Make use of our services

For your convenience, we have gathered relevant downloads in one spot. If your question is still unanswered, please feel free to contact our Energy Support Team.

Contact the Energy Support Center

Energy Customer Support

+49 180 524 70 00

+49 180 524 24 71

Energy Customer Support

Freyeslebenstrasse 1

91058 Erlangen



Making a difference

Rail operators and train manufacturers worldwide rely on Siemens Transformers expertise and experience for transformer designs that push limits and set records while affording maximum reliability.          

Streamlined for top-of-the-line performance

15 kV

Rated voltage


Rated power

0 Hz


The German Rail operators DB and DB Regio utilize this traction transformer for EMU applications in Desiro HC trains. The 4,850-kilogram unit is mounted on the roof and comes with a streamlined design – its air deflectors increase down-thrust and stability.    

Minimum in size and weight meets intelligence and maximum efficiency

15/25 kV

Rated voltage


Rated power

2000 kg


At 25% less weight, this 16,7/50Hz-frequency traction transformer for the new Mireo® regional train if the German rail operator, Deutsche Bahn, comes with a maximum power-to-weight ratio. Intelligent recording of maintenance-related data reduces life-cycle and maintenance costs while increasing safety and availability.

An allrounder for freedom across borders and voltage systems

15/25 kV

Rated voltage


Rated power

At 12,500 kilograms in weight, this 16,7/50Hz/DC-allrounder for heavy AC locomotive applications is mounted under the floor. Its impressive rated power and variable voltages allow trains to cross into nearly all European countries – no exchanging of locomotives necessary.    


Get a traction transformer for your application

You need a tailored transformer to solve your specific challenges? Talk to us. We will design a transformer that gets you right on track.