High-current industrial transformers

With their reliability, low losses, and maintenance-friendly designs, Siemens Transformers sets standards in cost efficiency.

Tailor-made and designed to withstand the harshest conditions, Siemens transformers provide power for industrial applications, in which current itself is a major resource – from steel manufacturing to electrolysis, from mining to offshore oil and gas platforms. Reliability and cost effectiveness are the main requirements to modern converter transformers. Find out in our exclusive whitepaper how you can specify your converter transformers to enhance your system stability while saving costs at the same time. If you operate furnace transformers you might be interested in learning what measures can be taken to further increase the reliability and lifetime of your transformers. Please find our whitepaper below.

Furnace transformers white paper

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Industrial transformers info package, ene 12, 2018

Important parameter for your specification

Do you need a tailored transformer to solve your specific industry challenges? Download our important parameter for your specification.

Important parameter for your specification

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Top performance meets superior environmental and safety standards

Furnace transformers as well as heavy-duty rectifier and converter transformers connect processes to the power grid. Their purpose is to supply a critical resource to energy-intensive industrial applications – high currents with very specific voltages. These transformers must meet rigorous requirements. Siemens ' expertise in design and precision manufacturing ensures customers enjoy top performance and efficiency in terms of both cost and energy. At the same time, units need to be extremely reliable in operation and environmentally sound while affording the highest level of safety for those working in their vicinity.

Heavy-duty powerhouses that withstand harshest ambient conditions

Siemens transformers are leveraged in very different environments, from mining to oil and gas extraction, from steel plants to chemical industries. Each area of application requires specific transformer designs to supply the right kind of power for very specific projects in very specific environments. Siemens transformers for all industrial environments. Their especially rugged designs withstand exposure to dirt, gases, short circuit forces, and high magnetic fields.


Siemens transformers built for industrial applications deliver extended voltage regulation ranges. They can provide extremely high currents and have the capacity to feed multi-pulse rectifier units to ensure low system perturbation. This allows them to withstand cyclic load and high thermal stress while remaining highly reliable. In addition, furnace transformers withstand frequent overcurrent and overvoltage caused by short circuits in the furnace or by tripped high-voltage circuit breakers.

Why Siemens Transformers

Design experience and market intimacy at your service

As a leading supplier for over six decades, Siemens not only brings more than 100 years of experience in transformer technology to its industrial transformers but a production and service network that spans the planet. This global network keeps response times short, ensures just-in-time delivery, and gives you the same extensive know-how and the same technology and quality wherever you are.    

Rich customization options and unique designs

Siemens Transformers translates individual customer requirements into unique premium-quality transformers with a reputation for superior reliability and an impressive service life. Siemens has developed a wide range of design options to ensure its tailor-made transformers cover all customer use cases.

Design options for high-current transformers for industrial applications

Specifications for voltage, power rating, ambient climate, network topography, and noise level are typical transformer criteria.
Further design options include:

  • Cooling and extreme-heat protection
  • Oil-directed cooling designs for high power densities in small installation places
  • Transducers – rugged technical designs for voltage regulation as an alternative to electrical parts
  • Defined earthing and electrical grounding to avoid loop currents
  • Direct or indirect voltage regulation
  • On-load or off-load tap changer
  • Compensated lead connection designs to decrease magnetic fields
  • Shielding designs to decrease the effects of high magnetic fields
  • Monitoring

Cross-benefitting from breakthrough innovations

Within its Global Technology Center, Siemens has dedicated two Centers of Competence exclusively to driving innovation in large and medium power transformer. As a result, Siemens transformers across the board benefit from design breakthroughs, even those originally achieved for other – sometimes more complex – transformer types. This ensures cutting-edge technology across the entire transformer portfolio.

Superior performance density in minimum-footprint designs

What makes Siemens transformers stand out in the market is the superior performance density they bring to especially compact and lightweight designs. 

Protect your transformer assets

Siemens Transformer Online Monitoring System transforms service into reliability

The impact of transformer outages on the process industries in which they are used can be severe because outage costs may not be limited to the cost of transformer repairs. In industrial applications, an outage may result in standstills and a total loss of production. Related costs can quickly rise to a level that affects even larger organizations. An effective way to minimize this risk is the continuous monitoring of key parameters during transformer operation. According to an independent study, online monitoring systems can detect 60% of all typical transformer errors before they occur.

The 5 top benefits of the Siemens TDCM sensor

  1. Evaluate and time replacements with better accuracy
  2. Identify incipient faults and take action to avoid costs of a high-impact failures
  3. Potentially reduce of insurance indemnity for defects
  4. Gain a better understanding of operative conditions and control
    to further decrease costs and the risks of faults
  5. Benefit from predictive maintenance and optimize the maintenance process

Benefits of Siemens Transformer Online Monitoring System

The Siemens online monitoring system for transformers incorporates the most advanced analytical technologies. It helps to effectively reduce failure risks while increasing the efficiency of maintenance during operation.


Remanufacturing transformer originals

When a transformer reaches the end of its lifecycle, it needs to be replaced to maintain the operation. Although there are ways to fast-track replacements, ordering, designing, building and even delivering a replacement transformer generally requires careful planning well ahead of its installation. Siemens experts work closely with customers to reliably remanufacture transformer originals. Customer can choose a 1:1 replica or opt for a new transformer that fits into the existing vault or chamber but offers greater capacity.



Same dimensions, higher power density                     

In steelworks especially, the notoriously small transformer chambers set challenging limits for capacity expansion. Thanks to extensive expertise in cooling designs and in handling high magnetic fields, Siemens is able to offer higher power density with much smaller real estate requirements than the competition.    


The factory acceptance test, which Siemens transformers undergo fully assembled in Siemens own test bays, includes tests against standards specified by the customer. 

These standards include but are not limited to:

  • ISO 9001, 14001 for certified plants
  • The certification according ISO 29001, a standard important for customers in the oil and gas industry, is a unique advantage of the Siemens transformer production site in Dresden.
  • IEC 60076-1 for power transformers
  • IEC 61378-1 for converter transformers and as an additional standard for transformers for industrial applications
  • IEEE Std C57.12 is a standard for general requirements for liquid-immersed distribution, power, and regulating transformers
  • IEEE Std C57.17 describes the electrical characteristics and mechanical requirements for arc furnace transformers. This is a standard relevant to customers located in the US.    
Transformers Types

Powering industries

Siemens designs and builds a wide range of tailor-made high-current electric arc furnaces, rectifiers, and converter transformers for applications in process industries where power is a key resource.

Electric Arc Furnace Transformers

Transformers for melting processes

AC EAF transformers are specifically designed to withstand the exceedingly severe conditions accompanying metallurgical steel melt processes in

  • foundries,
  • in secondary steelmaking,
  • in ferroalloy production.

Technical features

  • Ratings up to 300 MVA
  • Secondary voltage up to 2 kV
  • Electrode current for steel up to 120 kA
  • Electrode current for ferroalloy up to 180 kA

EAF design options

  • Direct or indirect regulation or booster
  • On-load or off-load tap changer
  • Oil- or vacuum-type OLTC, also reactor-type OLTC
  • Series reactor (built-in or separate) for long arc stability
  • Air- or water-cooled secondary bushing arrangements and designs
  • Internal secondary phase closure (internal closed delta)
  • Special magnetic shield designs – a Siemens specialty
  • OF- or OD-cooling


Heavy-Duty Rectifiers

Transformers electrolysis and smelting

Heavy-Duty Rectifiers (HDR) are used for

  • industrial processes, which require a significant direct current (DC) supply. Typical areas of application are aluminum electrolysis or smelting operations.
  • high secondary currents, together with the harmonic currents generated by the rectification systems.

Technical features

  • Ratings up to 225 MVA
  • Secondary voltage 2 kV to nearly 0 V depending on the application

HDR design options

  • Direct or indirect voltage regulation 
  • Double-star or bridge connection
  • Double-tier design and/or keel line arrangement
  • Double-tier with or without intermediate yoke
  • On-load or off-load tap changer
  • Filter connection or filter winding
  • Additional phase-shifting windings for 12-pulse or higher pulse systems
  • Interphase reactor, saturable reactors (transductors)
  • Air-cooled secondary bushing arrangements and designs
  • Numerous different vector groups and phase shifts    

Converter Transformers

Transformers for large-drive industrial applications

Converter transformers

  • supply the input for variable-speed drives, e.g. for large-scale industrial drives, pump stations, rolling stock in mining applications, or blast furnaces.
  • allow multi-pulse (up to 36) rectifier operation.

Technical features

  • Ratings up to 200MVA
  • Secondary voltage between 800V - 36kV, depending on the drive
  • Additional winding to filter harmonics
  • Combination with a frequency converter

Design options

  • Double-tier or multiple-tier design
  • On-load or off-load tap changer
  • Filter winding and/or earth screen
  • Various vector groups and phase shifts
  • Variable-speed drive design
  • ATEX certification
  • Operation in harsh environment
  • Alternative insulation liquids    
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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.

Ready to meet any challenge

Solving the specific challenges of each customer, Siemens Transformers brings expertise, superior technical design, and rigorous dedication to quality to transformers for every kind of application. As a result, customers benefit from transformers with trademark low failure rates, exceptionally long service life, and a track record of cost-saving operation.       

Active-part cooling for mass-optimized replacement transformers with increased ratings

150 MVA

max. ratings capacity    

0 kA

max. electrode current for steel    

0 kA

max. electrode current for ferroalloy

Siemens used oil-directed cooling to build a mass-optimized transformer replacement for Gerdau Steel, in Georgia, USA. At a total mass of 96.9 tons per 100 MVA, this unit comes to less than a ton per 1 MVA.

Mastering one of the most complex transformers ever built

0 ratings

46.8 / 4x16.5 / 20 (filter) MVA    

0 ratings

132.0 / 4x 0.509 / 23.7 kV    

15000 kA

current x4

Boasting a double-star connection for a 24-pulse diode rectifier and a high HV voltage, this highly complex rectifier transformer for Asturiana de Zinc, Spain, is a feat of design and engineering. Connections include a YN a0, D y337.5° y157.5° + Y y7.5° y 187.5°, with interphase reactor and transductors. With a maze of voltage subsystems, this rectifier transformer sits in the tank of another active component and uses interphase reactors und transductors.

Landmark safety and top performance


pulse converters fed by 4 low-voltage systems in double-tier


Atex certification for ex zone

0 kV

rating with 4x 2.0kV ± 5 % (NLTC) and 16/4x4MVA

This design comes with unique safety features. It boasts a Sergi explosion prevention system and a high-performance liquid insulation medium that is fire safe, robust, and biodegradable. ZADCO in Abu Dhabi, UAE, uses this transformer for offshore oil and gas extraction in an environment too hazardous for conventional designs.


Get in contact with our Sales Support and Customer Service for Power Transmission and Distribution

Do you need help on a concrete project? Do you need a quote for any of our products or solutions? Do you need support for your installed equipment? Do you have a technical question? Do you need something totally different? You can contact us 24/7. We are looking forward to your call or online request. Phone +49 180 524 70 00