This series brings topics answering basic questions around VFDs such as fundamental components of VFDs, drive system components, working principles, dimensioning considerations etc.
VFD catalog rating You have surely noticed that most manufacturers have catalogs and brochures with tables listing their VFD types along with basic information such as rated output current, motor shaft power, cooling requirements, enclosure type, dimensions, weight etc. What is behind this VFD catalog rating and how to understand 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 an amendment to the LCI vs VSI series [1] that 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
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 look like? What are the features of your dream VFD? Read more
Motor start with VFD Our experience shows that the VFD motor start is sometimes not fully understood. This post shall explain how motor start with VFD works, what are the main benefits and how does it compare to a direct on-line start. Abbreviations AFE = Active Front End DFE = Read more
Acoustic noise level This post discusses the topic of noise generated by variable frequency drive system. We will talk about acoustic noise in applications utilizing VFD technology. To be precise we shall use terms of sound pressure level and sound power level as explained further. Acoustic noise and health Why Read more
Combined transformer Our recent post [1] walked the reader through the two main VFD transformer options: integrated transformer and external transformer. Today we will introduce a solution that aims to leverage on advantages of both solutions: combined transformer. The name might be a bit misleading. We can also call it Read more
Integrated versus external transformer Modern variable frequency drives offer two options: integrated transformer or external transformer. How do these options compare? Which one is a better choice? INTEGRATED TRANSFORMER EXTERNAL TRANSFORMER There is no general answer. Instead, it depends on several aspects and project specific conditions. This post will walk Read more