This series brings topics answering basic questions around VFDs such as fundamental components of VFDs, drive system components, working principles, dimensioning considerations etc.
What makes protection firing so brilliant? Protection firing, sometimes also called “firing through”, is a VFD protectionconcept used in some medium voltage drives. The principle is well described in its name:In case of a severe fault the VFD will turn on all the active switches (such as power semiconductors in Read more
What is behind the recooling of electric rooms? VFDs generate certain heat load that is dissipated into the ambient. Despite the high efficiency of the VFD, there is some portion of losses that heats up the electric room where the equipment is installed. Hence, it is important to ensure proper Read more
Scalar control – What does it actually mean? Many times we see that the term ‘scalar control’ is used in incorrect way or being misinterpreted. In this article we will briefly discuss scalar control – what does it actually mean? How does it differ from a field oriented control? What Read more
What VFD properties matter the most to you? Medium voltage VFD is often a long term investment. The expected lifetime is typically at least 20 years. Thus, it is important to make the right choice when purchasing it. That is easily said, right? But there are several products on the Read more
Why do VFDs sometimes trip during grid faults? Grid disturbances and faults appear now and then. And it is desirable that the VFD does not trip every time such event occurs. Thus certain immunity against grid disturbances is desired. In fact, many products claim to have a capability to withstand Read more
KYDS: Know Your Drive System KYDS -Know Your Drive System – is our new program where you learn more about variable speed drive system and the most important system components (transformer, VFD, electric motor, cooling system, harmonic filter). Scope of KYDS The scope of the Know Your Drive System program Read more
What is the difference between VFD and VDS? This article aims to answer one relatively simple question: What is the difference between VFD and VSD? As the question was raised again recently, we would like to deliver an understandable explanation. Let’s start with the abbreviations first to ensure that we Read more
How to measure VFD efficiency Energy efficiency is high on the agenda. VFDs are enablers on higher efficiency in drive systems, especially in flow control. However, how to deal with VFD efficiency? In particular, how to measure VFD efficiency and verify the figures provided by the manufacturer? There is a Read more
Active filter or AFE drive – What is a better option? When taking care of grid harmonics there are several technical solutions to choose from. You might stand in front of a dilemma: active filter or AFE drive? What is a better choice? Nowadays there are multiple approaches how to Read more
How does VFD calculate the motor torque? Motor torque along with speed is the most important quantity that the VFD shall control. But how does the VFD measure or calculate the motor torque? What are the necessary inputs? Are there any extra sensors needed? Can every VFD perform the calculation Read more