Abbreviations
VFD/VSD/ASD/SFC and more!
Confused about all the different abbreviations, acronyms and naming? Let’s start with a short explanation. Or maybe just a refresher:
VSD stands for Variable Speed Drive. It is often used as synonym to VFD. However, VSD has broader meaning. It is a general term for anything that varies the speed of motor
driven load (AC drive, DC drive, eddy current clutch drive, hydraulic variable speed drive
etc.). The speed is controlled electrically or mechanically.
VFD means Variable Frequency Drive. The term refers to a power electronics converter that provides the ability to convert a fix supply frequency (typically 50 Hz or 60 Hz) into variable frequency of the motor in order to control its speed. It is an equipment controlling the speed of AC motor by altering frequency and voltage of the motor. Therefore, VFD is used for purely electrical speed control of motors. For example, DC drive is a VSD, but not a VFD.The abbreviation VFD is probably the most correct when talking about power electronic converters for motor drive applications.
ASD means adjustable speed drive. The meaning is similar (equivalent) to VFD. The term ASD is frequently used in North America.
SFC stands for Static Frequency Converter. The use is a bit tricky as the meaning is quite wide. The abbreviation might be used for motor drives or soft starters (e.g. ‘older’ LCI converters) as well as frequency converters in other applications such as wind converters, grid interties, excitation systems etc. The original purpose was likely to differentiate the equipment from rotating frequency converters (motor-generator sets).
Above terms refer to the (power electronics) frequency converter only. When we talk about a system (input transformer, VFD, motor etc), the terms VSDS (Variable Speed Drive System) or PDS (Power Drive System) are most commonly used.
Still confused? What acronyms do you usually use? Write a comment on feedback@mb-drive-services.com.