Most publications celebrate new, unproven ideas. But DrivesMag is all about work. So we like ideas that work.

Eaton has a clear winner in the Ampgard® SC9000.

The judging is complete and Eaton's Ampgard® SC9000 Medium Voltage Drive has won DrivesMag's first annual Old Idea Contest. Out of dozens of great submissions, the Eaton team showed why theirs was the best. Old ideas are at least 5 years old, and can been proven, by customer feedback, to be good and worthy of a recommendation.

What does a customer say about the SC9000?

The Benton Irrigation District in Washington state needed to replace a deteriorating open canal system. This included a reliable pump station at the Yakima River to supply water for 4,630 irrigable acres crucial to its agricultural industry. A new pumping station was constructed above the Yakima River to accommodate for current and future irrigation needs with six of Eaton’s Ampgard® SC 9000 medium voltage adjustable frequency drives.

Joseph Dinkel, the executive director of operations at the West View Water Authority tells the complete story:

Albeit that the pumps were new, modern pumps and they utilized state-of-the-art starters and pump control valves, we were still having a very large [energy] demand.

After visits to the [Eaton test facility] factory, where the products [Ampgard® SC 9000 medium-voltage drives] are manufactured seeing their [Eaton] availability to support us, we were quite satisfied that Eaton had the ability to handle this project.

We had Eaton products that serviced the original facility, and as a result the transition into the Eaton variable frequency drive (VFD) mitigated the amount of construction that was necessary for the project and made it a seamless transition into the new operation.

We rarely shutdown the units [Ampgard SC 9000] and they provide a very high degree of reliability on a 24 hour-a-day basis.

The Eaton drives allow us to operate 24 hours a day. When they [the Ampgard SC 9000] are online, we have less main breaks due to trauma placed on the system due to the starting and stopping of pumps.

With the new system, when the motor starts, there are no in-rush problems. It starts very slowly. Everything is under controlled circumstances. Where the motor [is], you can actually see the RPM start slowly. When it gets up to the point where we want it, it will produce the exact amount of water that we want with no wasted energy.

The very first month that the system was online, we documented that we were saving a thousand dollars a day, so that’s obviously thirty thousand dollars per month. And the way I prefer to look at it, over 3 years, we’re talking a million dollars in savings.

Eaton was tremendous to work with throughout the entire project. They provided excellent guidance for our electrical consultants during the design phase, for the specification writing, for the bidding process and for the implementation.

Our Eaton project has been such a success that we are totally convinced that the VFDs are the way to go in the future. We have a new plan that we are designing and it will be using VFDs at the intake, and throughout the treatment facility, and on the high-service end of the pumping operations.

As the winning company, Eaton will receive a free year-long banner on the DrivesMag home page, and the winning submitter will get a new iPod touch. Congratulations to the Eaton drive team, and thanks to Joseph Dinkel and the West View Water Authority for sharing your story!

This from Rick Idle's blog on water treatment systems engineering:

Direct or fixed speed drives on centrifugal pumps are the most common choice for reverse osmosis (RO)systems. This is because the operation is simple and once the required flow rate and total head (i.e.,pressure) has been specified, the pump only operates on that pump curve. The direct speed drive type of design is well suited to applications where the feed water temperature is relatively constant or the variability of temperature is low, probably less than 5°C between high and low temperatures.

VFDs (Variable Frequency Drives) on centrifugal pumps should be considered when there is greater than 5°C difference between the low and high feed‐water temperatures. The use of VFDs allows you to use less energy because you operate on more than one pump curve depending on the feed pressure required. Capital cost of the VFD is higher, but operating cost is lower due to energy savings.

RO membranes require control of feed and brine flows and pressures to accommodate changes in feed water temperature, feed chemistry and membrane fouling. This important function should be handled by the integrated RO system. The optimal solution is to use a VFD to change pump‐operating speed as required for the desired feed pressure without energy-wasting throttling.

The VFD provides efficient control of the pump discharge pressure by control of the pump operating speed. The VFD also eliminates the need for a throttling valve and allows for super‐soft motion starting and easy regulation of feed water pressure.

This video, by AC drive and motor expert James Shumberg, introduces induction motor theory and offers tips on proper motor selection for motors used on AC drives. Part I of 4.

Treating harmonics in VFD applications is important in order to ensure that power quality problems are averted but this need not come with a sacrifice in energy efficiency. Find out how.

Harmonic currents generated by conventional 6-Pulse Variable Frequency Drives (VFD’s) have been known to cause distortion of the applied voltage leading to power quality issues. To eliminate this concern, low harmonic generating 18-Pulse VFD’s are often specified at a significant premium. Although 18-Pulse VFD’s are very effective in eliminating harmonic problems, they are often at least 2 - 3% points lower in efficiency than conventional 6-Pulse units. This is primarily due to the losses associated with the phase shifting transformer and the extra reactors required to reduce harmonic currents. A more cost effective, alternative method which achieves equivalent or better harmonic reduction without the sacrifice in energy efficiency combines a standard 6-Pulse VFD with a passive universal harmonic filter.

By Dick Orndorff, Square D / Schneider Electric, Raleigh, N.C.

Specifying AC drives in Division 16 of electrical specifications is critical to optimizing the cost efficient operation of an industrial plant. Understanding and accepting this assertion requires familiarity with how AC drives can be applied, including their compatibility with motor control centers (MCCs).

In the past, AC drive designs of Variable Voltage Inverters (VVI, 6-step adjustable frequency), adjustable voltage and wound rotor controllers, were nearly always specified in Division 15 of mechanical specifications, because of motor coordination issues. Today, with the modern pulse width modulated (PWM) adjustable frequency drive, motor coordination is simple due to the quasi sine wave current output waveform, excellent motor torque per ampere performance, reduced motor heating and built-in solid state motor overload protection. Consequently, the considerations in deciding whether or not to apply a PWM AC drive today have changed.

Recently, Variable Frequency Drive (VFD) manufacturers have seen a trend to move the VFD specifications from the mechanical portion of the specification (section 15XXX) to the electrical portion (section 16XXX). While this trend may stem from concerns about harmonics, it may also be influenced by certain VFD manufacturers who have a vested interest in having the drives specified in section 16XXX. Another reason for this trend may be that mechanical department personnel at consulting firms are often not comfortable with the harmonics issue. It is the writer’s opinion that specifying VFDs in section 16XXX can cause unnecessary concerns. This article will document some of the more compelling reasons to place the drive specification in the mechanical or controls section of the specification. This article will also document some of the potential pitfalls possible when installing the VFDs in MCCs (motor control centers). Finally, recommendations for specifiers will be presented.