© 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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