Photo contest We are sure that there are brilliant photographers among our readers. Therefore, we decided to organize a small photo contest. Yeahh! Do you have any interesting photo regarding variable frequency drives, motors or transformers to share with us? Read more
Current source and voltage source inverter Current source and voltage source inverter are the two basic types of indirect frequency converters. Therefore, it might be very interesting to describe and compare both types. This article can also be seen as Read more
LCI versus VSI:60 MW case study Introduction In this post we share some results of a case study comparing load-commutated inverter (LCI) and voltage source inverter (VSI) for a 60 MW variable speed drive system. Due to confidentiality some quantities 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). Read more
Dream VFD You may think that the title of this article – dream VFD – does not sound very serious. However, let us elaborate on the topic a bit. It actually is a serious question: How does your dream VFD Read more
Sustainable drive systems throughout the entire life cycle Sustainability is a popular word in today’s dictionary. In our opinion this is very good as long as the efforts are sincere and it is not just marketing. Variable frequency drives (VFD) Read more
Harmonic filters The continuation of our “Network harmonics” series [1] presents an article about AC harmonic filters. We explain the purpose of harmonic filter. Different types of harmonic filters are shown. Several design considerations are discussed. Main items are illustrated Read more
Trolleybus Skoda 9 Tr Lot of cities nowadays invest in more environmental friendly public transportation. Due to that trolleybuses experienced a renaissance in the last couple of years. Many cities that used to have trolleybus lines and discontinued their operation Read more
Network harmonics: Mitigation methods Today’s post focuses on harmonic mitigation methods. Let us review the most common, well proven methods of minimization of harmonic distortion on the grid side. Previous articles presented a general view on harmonics, their origin and Read more
VFD harmonic spectrum Introduction After the theoretical introduction [1] we jump to variable frequency drives as sources of harmonics. This post is about VFD harmonic spectrum. As already mentioned, VFDs belong to non-linear devices with non-sinusoidal currents and/or voltages that Read more