This series about various aspects of variable frequency drive (VFD) dimensioning
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
Power, speed and torque The purpose of variable speed drive systems is basically the ability to provide required torque at corresponding speed. In simple words: to turn the shaft. Of course, the quantities of power, speed and torque are coupled together. This article is a bit more theoretical review. However, Read more
Multidrives and their benefits Multidrive concept is a VFD solution where multiple motors are supplied and controlled from one VFD having several inverters connected to a common dc link. This concept has several advantages and is especially popular in certain applications, for instance rolling mill drives or specific test stands. Read more
Load types and characteristics Type of load is relevant for VFD hardware dimensioning and selection of most suitable VFD topology [1]. Sometimes the load type determines what kind of rectifier (front end) is required. Also, load type may affect some options and features that the VFD shall have. Therefore, it 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
Long motor cables Today we gonna talk about long motor cables and their impact on drive systems. In some projects the physical distance between VFD and motor as well as cable routing cause motor cables to be fairly long. This fact has impact on system design. The motor control might Read more
High altitude Majority of variable frequency drive (VFD) systems is installed at altitudes below 1’000 meters above sea level (masl). In such cases no additional considerations due to installation height apply. However, there are sites located at high altitudes. How does it impact the VFD and other drive components? What Read more
Derating and uprating factors What is the power rating of the specific VFD? An indicative value is provided in the technical catalog or brochure. This value shall refer to certain operation conditions, among others the temperature of cooling medium (air or liquid), content of anti-freeze additive (usually some type of Read more