You’ve heard the news, you’ve jumped on the wagon, and now you’re enjoying the ride. A drive-controlled, permanent magnet AC (PMAC) motor is the new standard for the industry—no matter the industry. Whether you call it a variable-frequency drive (VFD), a variable-speed drive (VSD), an inverter, or an AC drive, you’ll need one, alongside the PMAC, in every application that comes your way. However, while the name selected to describe the technology does not make a difference, there is a consideration that just might make a big difference in your application. It might seem simple, but considering the difference between a drive that has been integrated into the body of the motor by the manufacturer and a drive that you’ve selected from another manufacturer will be important for your future strategy.
First, let’s make sure we’re all on the same page with the technology. The PMAC motor most often works by making use of permanent magnets in or on the rotor and windings in the stator. In order to create rotary motion, the current flowing through the stator windings must rotate. Traditionally, this is done with an alternating current such that the frequency controls the speed. Therefore, in order to control, or at least vary the speed of the motor, an engineer must make use of a system that can vary the frequency of the current flow in the stator. This varying frequency is created by the VFD, VSD, or the myriad other names which permeate the corners of our industry.