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…
Current, voltage and power scaling of VFD Variable frequency drives (VFD) became unthinkable part of industrial motor drives. They cover voltages from some 120 V up to 13.8 kV (special designs go even higher) and power range from fraction of kW until 100 MW and beyond. Enabler of such wide Read more…
Advantages of liquid cooled drives This article deals with liquid cooling for high power variable frequency drives (VFD). What is the principle of liquid cooling? What kind of liquid can be used for cooling? What are the advantages of liquid cooled drives? Continue reading this post on advantages of liquid Read more…
VFD testing: Introduction Abstract This new series on VFD testing will guide you through various aspects of testing of variable frequency drives (VFD) and drive systems. We will discuss tests required by standards (particularly IEC), factory acceptance tests, site acceptance tests and system tests, such as full load combined test Read more…
How to maximize the availability of your drive system Availability is one of the key criteria for the end users according to numerous surveys and direct feedback. Unplanned downtime is simply too expensive and shall be avoided. At the same time multiple redundancies may not be economically viable (high investment Read more…
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…
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…
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 with figures and pictures. Grid side filters are covered in 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 they draw from the grid or inject into the grid. Read more…