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?
What is transformer K-factor? Transformers supplying power electronic equipment are exposed to non-sinusoidal load current. The harmonics cause additional losses in the transformer. One way to express the transformer design with respect to immunity against harmonic distortion is so called K-factor. Since transformer K-factor is a potential source of confusion, Read more
What are the transformer guaranteed values? Like other electric equipment also transformers are generally designed in accordance with international standards. There are multiple parameters stated in the technical specification or a data sheet. However, which of them are the transformer guaranteed values? And what does the guarantee actually mean? Does Read more
When is transformer tap changer needed? The input isolation transformer in a drive system may be equipped with a tap changer. Such device provides some flexibility but adds cost and potentially also complexity to the transformer design. Thus, the question is whether a tap changer is needed or not. The Read more
How do ONAN and ONAN/ONAF transformers compare? Oil natural – air natural (ONAN) and oil natural – air forced (ONAF) variants belong to the most common oil-filled transformer cooling designs. This post compares both of them with regards to dimensions, losses, sound level, reliability or equipment price. Welcome to ONAN/ONAF Read more
When is transformer pre-magnetization recommended? Some medium voltage drive systems feature a pre-magnetization unit. In certain VFDs the pre-magnetization might be a standard. Other VFDs offer such functionality as an option. And most VFDs probably do not have the pre-magnetization at all. No wonder that some end users may be Read more
309 days on site! 309 days…that is exactly how long our rental transformer was on site. This example illustrates the importance of a backup solution when you experience fault of a VFD transformer. It was the beginning of December 2021 when we received an inquiry to rent a drive transformer. Read more
How to take oil samples properly? In this short blog post we share a basic guideline and set of recommendations how to take oil samples properly. Introduction Analyzing the quality of transformer insulation oil by means of oil samples is a standard practice used for decades. Important is to keep Read more
Success story on transformer rental for critically important compressor drive End of last year our company had the opportunity to rent the VFD transformer to support an important European production plant of a global chemical company. This case has proven our capital spare transformer concept. Learn our success story on Read more
Transformer design and cost drivers Right now the transformer prices are just sky rocketing. So talking about transformer cost drivers may be like bringing wood to the forest. However, we hope that the world turns normal again. Then, in normal days, there are specific design features and accessories or options Read more
Root cause of VFD transfomer failures Before we dive into the topic let us stress the fact that transformers belong to very reliable electric equipment and their failure rate is very low. This statement is generally valid also for VFD transformers. But no matter how reliable a certain device is, Read more