HTT - the transformer manufacture

Workpieces of passion - innovation from experience:

The HTT Hochspannungstechnik und Transformatorbau GmbH is successful since 1985 as a supplier of resin-encapsulated transformers and oil-immersed transformers in the national and international market.

Every transformer from the house HTT is a very special one. Highly competitive, individually planned or as a proven standard solution. Always in manufacture quality "Made in Germany".


New! Our HTT transformer concept -
Flexibility in a new dimension of Cast Resin Transformers


HTT kurz und bündig: De
HTT brief general survey: En

Ar Cn Cz Es Fa Fr Hu It Jp Kr Pl Pt Ru Tr

Station supply

In a substation (power distribution station), the electrical energy from the medium-voltage power grid with an electrical voltage of 10 to 36 kilovolts (kV) is transformed to the 400/240 volts used in the low-voltage power grid (local grid).

HTT transformers fulfil the high demands on quality and safety that are made on transformers in a substation. They are mechanically and thermally stable to varying load and harsh climatic conditions. More than 50 years experience in transformer construction, precision craftsmanship and the most modern manufacturing techniques are guarantees for low no-load and short-circuit losses together with high energy efficiency and at the same time low investment costs.

HTT transformers additionally operate extremely quietly as a result of careful core dimensioning. On account of the variable HTT manufacturing system, the transformers can be suited ideally to spatial conditions on-site.

Oil production

Oil is the lubricant of industrial economies. On account of resources becoming scarcer, oil production takes place in increasingly remote areas and under increasingly difficult conditions. Harsh salt-containing sea air offshore, arctic cold, tropical climate or hot desert air onshore are environmental conditions that make high demands on the transformers used there. Safety, longevity, energy efficiency and the adaptation of the transformers to local conditions, in addition to the electrical design of the transformer, are a basic prerequisite for the safe supply of energy to the oilfields of the world. There are no off the shelf made-to-measure solutions. Often, the difference is in the detail. HTT transformers afford the highest safety: in addition to the relevant transformer standards, HTT transformers also conform to the special requirements of the international classification societies.

Silicon production

Polysilicon is indispensable for applications in microelectronics, power electronics and in photovoltaic technology. After extensive distillation steps, trichlorosilane is thermally decomposed on heated high-purity silicon rods while adding hydrogen. The elemental silicon in this process grows to rods, which initially have a diameter of about 10 mm. After the reaction process in "deposition reactors" these rods have diameters of up to 300 mm with a length of up to 2 m. This process takes up to a week. As in any chemical process, constant temperature control is necessary over this period. In addition, the energy supply of the reactor has to be safely and reliably guaranteed during the entire period.

This complex chemical process in polysilicon production makes very special demands on the transformer employed. As one of the market leaders in the field of transformer construction for polysilicon production, HTT manufactures transformers providing variable voltages for different current loading in a single transformer. Hundreds of HTT transformers are successfully in use worldwide, especially for this complex process.

Petrochemical industry

To minimise production stoppages, to increase productivity and operating safety, to reduce energy costs, these are the requirements in petrochemistry. The reliable energy supply of the most different process plants is uppermost here and directly dependent on the production of petrochemical products. For petrochemistry, HTT offers individual solutions for sector-specific applications.

The energy consumption of a refinery is essentially determined by the plants for crude oil distillation, for reforming and by the catalytic and thermal cracking process. Since these processes run as one continuous process, a very high level of plant availability is required and thus an absolutely reliable energy supply. Whether converter transformers for 6-pulse inverter operation or as double-decker transformers for 12- or 24-pulse inverter operation or as a triple-decker transformer for 18-pulse inverter operation, we at HTT offer you solutions with the in each case technically and economically best choice of the conducting and insulating material for use.

HTT transformers – as individual as your requirements.


In the arc furnace process, electrical and chemical energy is used for melting the feedstock. The melting time, which essentially depends on the electric power of the furnace transformer, is crucial for production. Rapid cycle times between melting time, tapping operations and downtimes necessitate safe, robust and well-constructed transformers. The furnace transformer must be dimensioned such that a constantly changing, specific electrical power is safely available. Often, the transformer is accommodated in the immediate vicinity of the furnace, i.e. the ambient temperatures or cooling of the transformers likewise play a special role in the design of the transformer.

The furnace transformer transforms the voltage from a few 100 V to a few kilovolts, which is supplied to the electrodes in the AC voltage furnace. The currents on the electrode side can reach high kiloampere values. Whether oil-immersed transformers or resin-encapsulated transformers ought to be employed – we at HTT offer you individual advice as early as the project planning phase, with you on-site or gladly also at our works in Hann. Münden.

Paper production

A modern paper machine achieves a production speed of ~ 1800 m/min for newsprint papers or tissue papers.

Currently, paper machines produce up to ~ 2000 m/min. The dimensions are currently approximately 12 m working width and a total length of over 100 m, the total height reaches to over 2 stories. The paper web is rolled up on a »tambour«. The weight of a tambour ranges from 3 t to about 150 t.

High productivity of the paper machine through the ensuring of a constant and reliable energy supply of the motors and drives by the transformers used is very crucial for economical paper production. Therefore we at HTT consider all process steps of a paper machine as a whole. Paper can be produced conserving resources and with high efficiency only if the transformers involved in the process are technologically sophisticated and coordinated with the switchgear. We at HTT offer you transformers in manufacturing quality, which technically and economically correspond to every aspect of your requirement profile.

Test facilities

Every electrotechnical product, from a simple light switch to large motors of several megawatts, must be tested according to internationally very different standards. Every manufacturer of electrical equipment must therefore have a test facility tailored to its requirements, with a transformer as an energy supply that is constructed for the necessary investigations of the products. For us as transformer manufacturers, each test facility transformer is therefore a unique specimen with very specific properties, which can be defined only in close consultation with the customer. Whether high currents flow or many low-voltage tappings are required, no matter to what input power the transformer is connected – test facility transformers are exclusively special transformers that make special demands on us as transformer constructors.

Oil drilling platforms

Appr. one third of the oil produced originates from platforms in the sea. 85 per cent of the worldwide reserves are suspected to be there. However, offshore production poses particular risks. In order to minimise them, the equipment components necessary for production must be especially safe and operate absolutely reliably. Not least, this also applies for the transformers used on offshore platforms.

The resin-encased transformers of HTT exhibit the highest degree of operational safety, durability and reliability. They are designed for the most severe operating conditions. Thus for the harsh environmental conditions on offshore platforms, both the high-tension coil and also the low-tension coil are intrinsically cast under vacuum. By use of quartz sand as a filler, the thermal load can be lowered by more than 50% of the theoretically combustible material. The special support of the high-tension and the low-tension coil offers a high mechanical resistance to vibrations and mechanical stress.

All this, plus the know-how from over 50 years of transformer construction, offers you the highest level of safety on your oil drilling platforms in the ecologically sensitive world's oceans.

Marine propulsion systems

Since the introduction of three-phase alternating current in the wiring system of ships, a continual growth in the installed electrical capacity can be recorded for the wiring system. Three-phase induction machines have replaced steam engines or direct current machines as the drive of the auxiliary machines such as fans, pumps, air compressors, refrigeration equipment and winches. In cruise ships and some other special vessels, the propeller drive also takes place by means of electric motors. Extensive and powerful wiring systems are used, for which powerful transformers are correspondingly also needed. These transformers must be considered carefully not only from the electrical parameters point of view, but also be extremely robust mechanically, withstand the changing climatic environmental conditions on a ship and be constructed as compactly as possible from the space requirement point of view. This is not a contradiction.

Our HTT engineers daily design transformers that withstand extraordinary stresses and are designed for unusual operating conditions. This sounds expensive, however it is not. Even the economical aspect, the cost reduction, is considered extensively by us. Thus we continuously invest in our manufacturing techniques at our site in Hann. Münden.

HTT transformers represent high-quality solutions in the shipbuilding industry at competitive prices.

Container gantries

Large-scale lifting equipment and loading units are needed for the rapid loading of containers in the container terminals of sea and inland ports. With our help, container ships can be rapidly and efficiently loaded and unloaded. A gantry can handle ~ 900 t of trans-shipment operations per hour. The idle times for loading and unloading ships are becoming shorter and shorter. It is all the more important that the container gantries operate smoothly. Hardly in any other field does the adage “time is money” prove to be truer. Powerful, robust transformers are at the heart of container gantries. The current consumption of the container gantries is strongly dependent on the load of the container gantries. Rapid load changes, vibration-resistant design, low idle and short-circuit losses under harsh climatic conditions, these are the parameters according to which we design transformers for container gantries at HTT.

Worldwide, well-known customers from crane and container gantry construction trust in HTT transformers and know to value our competence, experience and flexibility.

Banks, public buildings

Banks and other public buildings no longer consist only of steel and concrete with a few electrical appliances for light and heating. In a modern building, functional processes must be performed automatically according to predetermined parameters. The entirety of monitoring, control and optimisation facilities in buildings is based on an ingenious “computer-aided facility management” (CAFM). Public buildings without programmable logic controllers or complex bus systems cannot be imagined. This CAFM must additionally be very energy-efficient to keep the operating costs as low as possible. None of this functions without transformers, which supply these systems with voltage. Special demands are made on transformers in building technology: low no-load and short-circuit losses, the lowest possible noise level and above all, a low purchase price, because economy is the key word here.

HTT transformers meet these requirements. They are extremely quiet as a result of careful core dimensioning and also have low no-load and short-circuit losses – at the same time with low investment costs. HTT standard transformers make this possible. In this construction series, the high-voltage coils are cast in embedded form under vacuum and the insulation material prepreg is used in the low-voltage coils. Aluminium is used as a winding material for HV coils and LV coils. The HTT standard range is obtainable as a grid distribution transformer or as a 6-pulse converter transformer.

Low investment costs and low operating costs without compromising on processing and quality, these are HTT transformers in manufacturing quality.

Coal mines

The mining industry and in general the exploitation of resources under and above ground are dependent worldwide to a high extent on energy. Most large mines are highly automated and thus energy-intensive. Overall, the mining industry cannot function without the use of large amounts of energy. This energy is needed for digging, drilling and excavation of mineral resources, for driving conveyor belts, sorting, screening and crushing any rock as well as for hundreds of other functions. In addition, equipment in the mining industry must be able to cope with the hostile environment full of dust, dirt, chemicals, dampness and contaminants from the air. The correct selection of transformers is absolutely essential. Heavy load cycles, thermal problems, very confined spaces (in which the transformers have to be of extremely compact construction) and the harshest environmental conditions have to be taken into consideration. The transformer must fulfil the requirements for safety, reliability and efficiency demanded, independently of whether it is installed on a tipper, must be suitable for carriage assembly or is designed for the starting of heavy motors. HTT offers a solution and not only a product.

Our engineers go about each of these challenges with passion to find the right solution for your application. This explains why our medium-sized business has successfully maintained itself in the highly competitive world market for more than 50 years.

Hydroelectric power plants

Hydroelectric power plants are gaining a higher and higher share of worldwide energy production. With a share of ~ 18 per cent of the worldwide energy supply, today water power is globally the most intensively used renewable energy source. In Germany, this energy source is exploited almost completely. Thus in Germany there are more than 7000 hydroelectric power plants, most of which are small power plants with a capacity of less than one megawatt. In addition to the heart of a hydroelectric power plant, the turbine, the transformer is one of the most important components.

Finally, a majority of the base load in the grid is covered using hydroelectric power plants and the coverage of the peak load is often guaranteed using the very dynamically controllable pump storage power stations. To meet the energy needs of communities and towns from hydroelectric power plants, more durable and efficient transformers are needed, which feed the energy obtained safely and reliably into the grid.

With our transformers, quality results even during development. HTT transformers are specially developed, constructed and manufactured to the requirements of the customer.

Examples of the worldwide employment of HTT-Transformers:

  • Station supply> more Information
  • Oil production> more Information
  • Silicon production> more Information
  • Petrochemical industry> more Information
  • Steelworks> more Information
  • Paper production> more Information
  • Test facilities> more Information
  • Oil drilling platforms> more Information
  • Marine propulsion systems> more Information
  • Container gantries> more Information
  • Banks, public buildings> more Information
  • Coal mines> more Information
  • Hydroelectric power plants> more Information
Return to overview - Resume slideshow