There once was a time when magnet motors and servo drives were the most reliable technology when it comes to precision motion control and motor. But today, a variable speed drive, also called variable frequency drive, is widely used with AC induction motors to attain high-accuracy motion. Once it is properly specified and designed, motion axes based on VSD or VFD offer the most cost-effective solution to motion control.
VFDs in Action
The first application for variable speed drives was to achieve huge energy savings and improved lifetimes for fixed-speed AC induction motors that are often utilized for rotating equipment and devices like fans, pumps, and blowers. Previously, the method to accomplish the variable speed or volume was to operate the motor at its highest speed while utilizing mechanical devices such as chokes, valves, cams, and gears to modify the desired results. However, this method proved to waste a lot of energy, makes the motor wear faster, complicates things, requires high maintenance, and creates more failure points. Enter the variable speed drive.
The drives allowed operators to adjust the motor speed directly without using any of those previous mechanical devices. This reduces the amount of power being consumed during the operation as well as the maintenance needed to keep the motor in good shape. Moreover, a variable speed drive is straightforward to use, reliable, and once properly sized and chosen, it offers great ROI.
In terms of control schemes, VSDs can use any of the four common control motor methods. These include volts per hertz (V/f) open-loop, V/f closed-loop, closed-loop vector control, and open-loop vector control. While a variable speed drive works really great, it does mean choosing it every time is the best option. The drive serves an effective solution for budget-sensitive applications that need only moderate positioning accuracies and resolutions.
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