We’re seeing more and more VFDs being used in water and waste water treatment. The water treatment VFDs that are of particular interest are the larger medium voltage VFDs.

The increased application of medium voltage VFDs to water treatment is driven by both process improvement goals, and energy savings.

Many plants are going from batch mode to a continuous process mode. In the past, water treatment facilities ran their pumps at full throttle to fill up storage tanks, and then shut them down at night. Water treatment facilities using medium voltage VFDs tend to run in continuous mode, and regulate the flow to meet demand. This results in less mechanical wear, and makes the chemical side of the process more efficient.

Although this is changing rapidly, I was sometimes surprised at what was a lack of familiarity with energy saving using VFDs in water treatment. We had a gentlemen at a water treatment plant tell us that his VFD was running at a fairly steady 54 HZ, so he didn’t see the need for it in terms of energy savings.

But, as I told him, that’s a 10% speed reduction, which all things being equal, amounts to a 28% reduction in energy consumed. On a 1000 HP motor, that’s a lot of dollars.

We are seeing more and more medium voltage VFD sales in water treatment driven by energy savings. There was an article in Water World magazine recently about a treatment plant reducing their energy costs by roughly $175,000 in one year on a 700 HP VFD. That’s a great return on investment, and it’s not uncommon.

Here’s where you will generally find medium voltage VFDs in water treatment.:

• Raw Water Pumps: These can range from 100 to 1500 HP, with medium voltage VFDs common at 500 HP and above. These pumps normally regulate water flow through the plant.
• High Service Pumps: These also range from 100 to 1500 HP, with medium voltage VFDs being common at 500 HP and above. These pumps are used to regulate pressure in the distribution system.

When do water treatment facilities go from low voltage to medium voltage VFDs? As a general rule, most applications at 500 HP and above should be considered for medium voltage. That being said, we’ve installed several 300 HP medium voltage VFDs. It depends on the circumstances.

Here are a few general rules..

IF you are concerned about power line harmonics (and you should be.. see “Harmonics, how do they affect your equipment?” ) then medium voltage VFDs have an edge. Almost all medium voltage VFDs have phase shifting multi-pulse inputs, and price-wise, that will often compare favorably to a low voltage 18 pulse VFD.

Cabling costs clearly favor medium voltage VFDs within water treatment plants.

Medium voltage drives, at 500 HP and above, usually have a smaller footprint.

IF you want to talk to us about applying a medium voltage VFD in your water treatment facility, then hit any of the contact methods on the right of this page OR call 770-448-4644.

The same if you need repair on medium or low voltage VFDs.

No one, Anywhere, is Better at Drives than We are..