This series brings topics answering basic questions around VFDs such as fundamental components of VFDs, drive system components, working principles, dimensioning considerations etc.
VFD switching frequency The heart of every variable frequency drive (VFD) is the power semiconductor. By switching on and off in a proper modulation scheme the frequency conversion functionality is achieved. Let’s look at various aspects of VFD switching frequency. Switching frequency of medium voltage VFDs Having medium voltage VFD Read more
Enclosure protection – IEC vs NEMA In this short post we look into the subject of ingress protection (IP) of enclosures used in variable frequency drives, switchgears etc. First we explain the classification of ingress protection according to IEC standard (“European practice”). Afterwards we introduce the North American practice defined Read more
What information belongs on a nameplate? Nameplate or rating plate is an inherent part of each drive system component, such as the transformer, variable frequency drive (VFD), electric motor etc. Therefore, it makes sense to spend few paragraphs on the topic. This post explains the content of information on a Read more
Which one is your VFD hero? VFDs, together with their rotating partners (motors) perform lot of work behind the scene. As we already know, there are multiple VFD topologies available on the market. While they all fulfill the basic purpose, such as soft starting of the machine and speed or Read more
Bypass in VFD applications Have you also come across that question: ‘What is actually meant with VFD bypass?’ This article presents 3 different meanings of bypass in VFD applications. Confusion about meaning of bypass I have noticed a common misunderstanding when talking about bypass in VFD applications that inspired me Read more
Braking capability of VFD fed motors Not every VFD is capable of active braking. And not every application requires active braking either. In today’s post we are going to review the braking capability of most common medium voltage VFDs. Let’s start with the need for braking. In fact, many applications Read more
Cell bypass – What you should know Today we will discuss the cell bypass in cell-based medium voltage variable frequency drives (MV VFD). What is the purpose of such bypass? How is it technically implemented? What happens when the bypass is activated? And finally, how does cell bypass impact the Read more
Best VFD topology: One size fit all? If you deal with variable frequency drives (VFD) you have certainly asked yourself the question: What is the best VFD topology? Why do the big brands have several different products in their portfolio? And is there anything like one size fit all? Does Read more
AC versus DC drive For decades DC drive was a preferred choice for variable speed motors due to its easy and accurate way of speed or torque control. However, the development of AC drives changed the competitive landscape and paved the way for AC drives. What was the reason for Read more
VFD control: An introduction In this post we introduce basic thoughts on VFD control. Some of you asked deeper questions about different motor control strategies and their benchmark. Such comparison will be subject of a separate post, resp. a dedicated motor control series. Today’s article provides a base for further Read more