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The Basics of Variable Speed Drives

December 18, 2019

The applications of speed reducers are endless and are ever-present, especially in industrial settings. They are found in pumps, elevators, conveyor belts, mills, and many other types of machinery crucial to the industrial sector. A speed reducer is also known as a variable speed drive (VSD) or adjustable speed drive (ASD). A variable speed drive is used to adjust or alter a motor’s rotational speed. As such, it is mostly used in motors, though they can be used in other rotary machines. So, what exactly is this device?


A variable speed drive controls the speed and torque of a motor by altering its input frequency and voltage.


The drive can either be mechanical, electric, or hydraulic. It is prized for its ability to control motor speed in a consistent and precise manner. Apart from its extensive industrial applications, a variable speed drive can also be found in common household items such as air conditioners, fillers, and big fans.


Two of the most important elements in a variable speed drive are its motor and a controller, which work in tandem to adjust speed. With these two devices working together, the drive is able to modify motor speed to attain more efficiency. The drive does this function continuously, eliminating the use of a step motor.


There are many types of variable speed drives, though they essentially fall under three major categories.

There is the mechanical adjustable speed drive, which is most often used in pulleys and belts. The second category is the electric or electronic speed drive, also known as the variable frequency drive or AC motor drive which is used in squirrel-cage and wound-rotor induction motors. The last category is that of the hydraulic adjustable speed drive, which uses hydraulic oil and is commonly used in pumping and mining applications.


As you can see, a variable speed drive is a complex machine with many functions. Talk to the experts at Bauer GMC today if you are interested in acquiring your own drive!