What is the optimal pulse number of a diode rectifier? Among variable frequency drives (VFD), the voltage source inverter with a diode rectifier is the most common all-rounder. However, there are several arrangements of the diode rectifier varying in the number of pulses. Is a 12-pulse rectifier sufficient? Do I 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…
Protection of VFD transformers In the introduction to this series we have explained the differences between a distribution/power transformer and a VFD transformer [1]. Due to different design, construction and operation of VFD transformers the protection requirements shall be adapted as well. While many end users, system integrators, EPCs and Read more…
VFD transformers and harmonics Introduction The next post in our series discusses VFD transformers and harmonics. We have already learned what harmonics are and how they impact the supply grid (Network harmonics – intro). In this series we look more specifically into harmonics and their impact on VFD transformer. Motivation Read more…
VFD transformers: Multi-winding design Today we look at the design of multi-winding VFD transformer feeding variable frequency drives. These VFD transformers are often classified in the category of ‘special transformers’. What does it mean? Why are they special? If you want to get these answers and a little insight into Read more…
VFD transformers: Introduction After reading this blog post you should understand the purpose of a VFD transformer and the differences between distribution/power transformer and a VFD transformer. Let’s start with the definition of a VFD transformer: This term refers to the input isolation transformer that supplies the rectifier section of Read more…