Wind technology

Decades of experience

Kohsel has been leading supplier of inductive components for the wind industry since its infancy in the 1970s. In fact, more than 100.000 wind turbines around the world include our components.

Decades of experience delivering inductive components for wind turbine converters has taught us all about the complexities of this dynamic industry. This has enabled us to develop solutions for today’s demanding applications, which calls for low losses and high efficiency combined with high energy densities and compact size.

Kohsel is a member of APQP4Wind

As the first transformer manufacturer in the world, Kohsel became member of APQP4WIND in 2020. APQP4Wind is a non-profit organisation founded by world-leading wind turbine manufacturers and suppliers. The background for APQP4Wind is the continuous quality improvement that is needed to keep pace with the ongoing trend towards decreases in the levelized cost of energy within the wind industry.

Some of our products

Liquid cooled grid reactor

Grid chokes from Kohsel are used in both onshore and offshore windturbine converters. The choke ensures that the alternating current fed into the grid exhibits a sinusoidal waveform.

Auxiliary (AUX) transformer

The auxiliary transformers provide the auxiliary power supply for installations inside the wind turbine.

Common mode reactor

The common mode reactor blocks high frequency noise while allowing the low-frequency signal to pass. Common mode reactors with nanocrystalline cores have a high attenuation over a wide frequency range, offering an extreme broadband attenuation.

Designing for the rising prices of copper.

We regularly deliver 120VA auxiliary transformers to a client in Germany. However, the drastically rising prices of copper and the associated higher costs of the transformer were becoming a problem.

All forecasts point to continuously rising copper prices, so we decided to redesign the transformer to optimise for this. But while the copper price continues to rise, the cost of lamination has started to decline. This was the reasoning for redesigning the auxiliary transformer to use less copper and more lamination.


  • Our redesign shifted the balance of the design towards using less copper and more lamination which caused an increase in winding loss while the core loss decreased
  • The cost savings for the customer were 4%
  • Cost savings will increase when the copper continues its rise
  • The client is less vulnerable to increasing copper prices

External reactors, chokes and filters

Line reactors

Reduce low frequency interference (harmonics) and relieve the strain on the grid network by compensating for the distortion reactive power induced.

Harmonic filters

Reduce current harmonics (THDi) to comply with the limit values required under the standards. This protects the connected grid network from circuit feedback and increases the system immunity from interference. Our LCL filters are specially designed to reduce harmonics of current absorbed by the rectifiers in the input converter.

Motor chokes

Reduce the voltage rise and the voltage spikes between the conductors which become more pronounced as cable length increases.

dV/dt filters

Protect motors against high voltage increases and voltage peaks at the motor terminal.

Sinus filters

Effectively protect the motor insulation and reduce supplementary losses and noise emissions from the motor. All-pole sine filters also enable the use of unshielded motor lines.

We are all about optimisation

At Kohsel, we combine technology, supply chain management and manufacturing knowhow in solutions that reduce cost at every step of your value chain and optimise performance through innovative and reliable technology. It’s this ability to optimise and reduce the total cost of ownership for our customers that sets us apart.

Our certificates

Kohsel is committed to providing customers with the highest-quality products, but also aspires to the highest standards of social responsibility and ethical conduct. Our core values support a strong commitment to economic, environmental and socially sustainable development.

At Kohsel, we make conscious choices every day. For us, it’s not about being the best – it’s about trying our best. We work continuously to improve our operations and develop our company in a sustainable direction.