© Jiří Tvaroh

Transformer cooling made easy

With the continuous expansion of towns and cities, transformer substations that once stood in remote locations are suddenly right in the middle of residential areas. To ensure there are no problems with the new neighbors, the Czech transformer manufacturer ETD makes sure cooling of its devices is particularly quiet.


Energy grids act as lifelines for modern society. Without their constant supply of energy, smartphones wouldn’t work, production would come to a standstill, and entire cities could no longer function. That is why the energy business is one that is built upon trust. Trust that consumers have in their energy suppliers, that energy suppliers have in the grid operators, and that grid operators have in their infrastructure. Transformers represent one important part of this infrastructure. The Czech company ETD produces transformers in Pilsen. ETD has just shy of a century’s worth of experience in manufacturing transformers, as the company has been active in the market since 1923.

Michal Svoboda, who is responsible for research and development at ETD, states: “Our long-standing involvement in the industry underlines that we are a reliable partner for our customers. After all, we’ve had almost 100 years to perfect our expertise. At the same time, however, we aren’t resting on our experience from the past; the requirements concerning energy grids are increasing, and, as a result, so are the wishes of our customers.” That is why ETD has been building increasingly larger and more complex transformers in recent years. This brings with it new challenges, both in terms of the trans­formers themselves and with regard to peripheral aspects, such as the cooling process.

Cooling – the straightforward way

Transformers are filled entirely with oil. It also surrounds the sensitive mechanical and electrical components. So that the oil doesn’t get too hot, it flows through a cooling radiator, which is assembled on the exterior of the transformer. In smaller transformers, the ambient air is often sufficient to cool the oil. Larger transformers, however, also require an active cooling process. One option for this is to have separate oil-air coolers — attached to the transformer, for example.

Svoboda explains: “Although these machines are extremely powerful, they form yet another complex technical system that is installed on the transformer, and which could leak — as a result of the transformer vibrations, for example. That is why customers often want a simpler and less fragile solution for the cooling process.” For ETD, this solution comes in the form of fans placed directly on the radiator, either at the side or at the bottom. These fans direct the ambient air right past the lamellae of the radiator, which is what enables the cooling process to work efficiently.

In recent years, ETD has been building increasingly larger and more complex transformers, which also pose new cooling challenges.

When searching for suitable fans, ETD was quickly drawn to ebm-papst. This was, in part, due to the specific search criteria laid out by the transformer manufacturer. As a result of increasing urbanization in many countries, transformer substations that once stood on greenfield sites are now often situated near or in the middle of residential areas. That is why one of the most important criteria for ETD is for the transformers to operate quietly.

“We quickly realized that the EC fans from ebm-papst aren’t just powerful, but also very quiet. Thanks to their continuous control characteristics, they also only ever operate at the speed required by the heat generation.” ETD was also impressed that ebm-papst offers suitable fans in all the necessary sizes for this task — right through to fans 1.25 meters in diameter for particularly large transformers.

Customized for the transformer

Michal Svoboda can still clearly recall one of the first projects involving ebm-papst fans. Back then, ETD was building three large transformers, each with a capacity of 350 MVA, for the Czech grid operator ČEPS. “Up until then, we had been using fans from a different manufacturer, but these weren’t available for this project in the right size, and they also weren’t quiet enough to satisfy the legal noise regulations.

We also wanted the new fans to be designed with the increasingly stricter ErP Directive in mind.” Svoboda quickly found what he was looking for at ebm-papst and was also delighted with the excellent consultation. “Even though we’re not purchasing huge volumes, ebm-papst modified the fans to fit exactly onto the cooling radiators of our transformers, which meant we didn’t have to alter the design in any way. This concerned the mounting and wiring of the fans in particular, as well as the options for fitting them onto the transformer.”

Fans from ebm-papst enable simple, efficient and quiet cooling — this is especially important in residential areas.

As a result, ETD was able to deliver the transformers to ČEPS on time and with the requested specifications. The machines have been serving the grid operator well for some years now, in a transformer station near Pilsen. Jan Dončuk, a specialist in technical strategy at ČEPS, explains: “The cooling process is an integral part of a transformer and plays a vital role in ensuring it operates reliably and for a long period of time. Quiet operation is becoming more and more important here. The transformers from ETD combined with the fans from ebm-papst meet all of these requirements. So far, there have been no issues with this combination, which is why I am very happy with the solution.”

“Even though we’re not purchasing huge volumes, ebm-papst modified the fans to fit exactly onto the cooling radiators.”Michal Svoboda – responsible for research and development at ETD

For ETD, the task commissioned by ČEPS was just the beginning of the collaboration with ebm-papst. These days, their transformers operate with ebm-papst fans of different sizes all over the world. “Some of our machines are sent to the north of Russia, while others can be found in Egypt. That is why it is essential that all of the components can deal with hot, cold, wet, and icy conditions. This applies to the fans in particular, as they are mounted in an exposed position on the radiators,” explains Svoboda. “At the moment we are designing and building a transformer that is to be stationed in Chile. In this case, one of the many challenges is factoring in safety when it comes to earthquakes.” It seems as though ETD still has plenty of work to be getting on with — even 100 years on.

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