VFDs save energy on centrifugal applications, where you don’t need to run at full speed all the time. Even a relatively small reduction in speed, can result in an exponential reduction in energy cost. And, since the cost per horsepower of VFD s has dropped significantly over time, while energy costs have risen, they’re a better deal than ever.
One argument against using VFD s in energy saving applications used to be that the added maintenance and complexity of VFD s, offset any savings you might otherwise enjoy. And at one time, that argument had some validity, but no more.
I’ve been in the electronic motor drive business since the 70’s, and VFD s have become increasingly reliable and simple to operate. Measured failure rates among the top manufacturers are remarkably low. That is a change from earlier days.
I remember starting a number of HVAC drives at a University out in Texas in a multi-story building. I would get one floor running, and by the time I got to the next floor, the ones I started had already experienced failures of some kind. My experience wasn’t unique, especially as manufacturers responded to downward price pressure at the expense of reliability. Thankfully, that has for the most part, washed out of the industry. We sell a large number of VFD s yearly, and see almost no problems with the new units.
And VFDs do save energy on centrifugal applications. There are some caveats; it must be an application where reducing speed is not only possible, but desired. Running a motor at full speed on a VFD will use more energy than it will running across the line, because there are some losses in the VFD, normally expressed as heat.
Using a VFD on a constant torque application may be a good idea for process reasons. It can even help with energy by reducing starting current, but it’s not really an energy saving application. Simply putting a VFD there won’t help in that regard. Typical constant torque applications are conveyors, positive displacement pumps,andextruders.
But the energy savings possible in common centrifugal loads using VFD s can be nothing short of remarkable. We have VFD s in applications where the entire cost, including the installation cost, was recovered in less than one year. And after that recovery, the energy savings are real dollars and cents than can go to the bottom line.
Think of it this way; if your plant sells its product at a 10% net profit, then every dollar you save in energy costs amounts to $10 in sales.
I’m not going to detail the “how” of VFD s saving energy. That’s settled science,. If interested, read Energy-savings-with-variable-frequency-drives here.
Medium voltage VFD s, which are always higher horsepower VFDs, offer very substantial savings, and because that’s a newer technology, are less common. When you begin to calculate the savings possible from (for instance) a 2500 HP medium voltage pump using a medium voltage VFD, they’re enormous.
Energy Savings using VFD s has been established science a long time. But, just as baseball teams return to Spring training every year, it’s good to revisit the concept, and look for savings in our facilities and plants.
Want to talk with us about it? Use any of the contact methods on the right of this page, or call 770-448-4644770-448-4644.
No One, Anywhere is Better at Drives (or saving energy with VFD s) than we are..