Converter duty transformers / rectifier duty transformers / VFD transformers – these are all synonyms for transformer supplying power electronic based converters. What is so special about these animals? How do they differ from a normal distribution or power transformer? How to protect these transformers and maximize their reliability?
DC component in VFD transformers Certain VFD topologies may generate direct current (DC) component on the grid side. There is a general concern about how such DC component affects the performance of the VFD transformer. In this post we discuss some basics of DC generation and its impact on transformers. Read more…
Purpose of electrostatic shield What is the electrostatic shield and why is it actually used? This article briefly explains the purpose of electrostatic shield in VFD input transformers [1]. First note that there are several terms being used for what we called “electrostatic shield” in the title of this article: Read more…
4 common defects of liquid immersed transformers In this post we present some of the common defects appearing in liquid immersed transformers. As stated at the end of this article always adhere to all applicable safety rules and regulations. Leaks of insulating liquid Despite high quality standards and best practices Read more…
Testing of Converter Transformers This post discusses some aspects associated with testing of converter transformers. Most tests performed on converter duty (VFD) transformers are same as those specified for power transformers. However, there are also few differences which are highlighted in corresponding sections of this article. The aim is to Read more…
Differences between IEC and IEEE design of transformers In this post, we are going to explore some of the differences between IEC and IEEE design of transformers. Our remarks are not valid for VFD transformers only. Instead, most of them equally apply for distribution and power transformers as well. Some Read more…
VFD output transformer Our VFD transformer series already guided you through many topics of VFD input transformers from their purpose, through multi-winding design and other design aspects, such as short circuit impedance or harmonics, up to protection or testing. However, there might be one more transformer in a variable speed Read more…
Tap changer: Yes or No? Shall a VFD transformer be equipped with a tap changer? What are the pros and cons of a tap changer on converter duty transformer? What kind of tap changer shall be used? How many taps does the VFD transformer have? This and more in our Read more…
VFD transformers: Differential protection Differential protection of VFD transformers might be a controversial topic. The more a reason for us to bring it up, explain the principle, describe the advantages and drawbacks and provide our view and recommendation for the users. We hope that this article will be useful source Read more…
Transformer short circuit impedance Short-circuit impedance of a transformer, impedance voltage or just impedance are terms often used as synonyms. They describe one of the most important transformer parameter: short-circuit impedance. This article, as part of our VFD transformers series [1], presents the short-circuit impedance from VFD design perspective. After Read more…
Dry type transformer technologies Transformers can be classified based on their insulation system in two major groups: liquid filled and dry type. Liquid filled (immersed) use either mineral oil or some alternative type of insulation liquid (silicon oil or esters). Dry type technology also has several sub-categories. The terms might Read more…