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22.07.2020 Products and Services

VACUTAP® VM® – A Worthy Successor for the OILTAP® M

Interview with then Project Manager Albert Schmidbauer

MR has successfully manufactured and sold VACUTAP®-brand vacuum tap changers, which offer countless advantages over oil-based technology, for many years. For this reason, many clients have fully switched to vacuum technology from MR.

In light of this, we have removed the OILTAP® M on-load tap-changer from our product range and stopped series production as of 31 December 2020. Then Project Manager Albert Schmidbauer discusses the advantages of the VACUTAP® series.

Mr. Schmidbauer, more than 10 years ago, you were tasked with developing a successor for OILTAP® M, MR’s best-selling tap changer. This product has recently been discontinued. What were the most important specifications for the project?

- The two main areas of focus were reliability and the ability to retrofit it into existing systems. It was also important for us to cover the versions of OILTAP® M that had been developed based on customer requests over the years. Our aim was to change the standard customer interfaces and customer handling as little as possible. We were able to achieve this by using the tap-changer head from the OILTAP® M in the new tap changers.

OILTAP® M is still considered a model of reliability and durability. How did you transfer these characteristics to vacuum technology?

- Primarily through decades of experience developing its predecessors, VACUTAP® VV® and VR®. This was the foundation that allowed us to pursue such an ambitious project. One important aspect was the development of a stable switching sequence across the entire temperature range, paired with the requirement for different oil expansion tank heights. We were able to secure the advantages of vacuum technology through the simultaneous development of a vacuum tube that was suitable for the power spectrum: minimal maintenance requirements coupled with an extremely long service life, absolutely reliable extinguishing of switching arcs, and maximum protection of the diverter switch against overvoltages. Furthermore, the tap changer was approved for the use of select alternative insulating fluids. All requirements were verified during development through more than 300 tests that were carried out on 100 VM® tap chargers.

Another challenge was ensuring that the VM® could be retrofit on existing systems. How did you do that?

- That was one of the biggest challenges! The installation space and connection interfaces in the oil compartment were prescribed by the OILTAP® M, which meant that we had a limited amount of space available.
After countless brainstorming rounds and design concepts, we were able to find a solution by cleverly arranging the modules, taking into account the necessary electrical clearances.

In the meantime, VACUTAP® VM® has proven itself thousands of times over. What kinds of applications do customers use it for?

- Both for network or generator operation as well as for challenging areas of application such as electric arc furnaces, HVDC, electrolysis, rectifiers and phase shifters.

OILTAP® M was essentially a workhorse in energy networks around the world for decades.
Now it has been discontinued. Do you think that its successor, VM®, will be as successful?

- I definitely do. This is made evident by the day-to-day customer demand. After four years, the number of VACUTAP® VM® tap changers installed exceeded the number of OILTAP® M. Until today, we have delivered more than 16,000 units in total.