These days, it's a pleasure for Mark Jensen to stand on his front porch and gaze at his fields across the road. In fact, he and his family spent a lot more time in the yard this past summer than they ever have. The reason? "We got rid of the diesel motor that powered the irrigation system - it was unbelievably loud," Jensen explained.
Not only did the noise irritate Jensen and his neighbors, the motor was a real pain in the wallet to maintain and overhaul. Oil changes, belts and other maintenance were necessary after every 200 hours of operation. Overhauling it — labor, parts and milling — every 10 years typically cost him anywhere from $6,000 to $10,000.
With single-phase service — and no real plans to upgrade to three-phase — Jensen didn't think he had an alternative to using a diesel motor until he met with Dale Bowe, an irrigation account executive with Wisconsin Public Service. Together they installed the first Written-Pole Ride-Through motor in WPS's territory, and it's performing as expected. The hidden benefit is that they got to know one another a lot better along the way.
"The Written-Pole Ride-Through motor is the first new technology in years that's been developed exclusively for use with single-phase service," Bowe said. "Growers will save time and money, which is great news these days." This new alternative to a conventional induction motor with a phase converter or a diesel engine can also run large equipment such as grain dryers, cranberry bog pumps or potato storage ventilators.
The Written-Pole Ride-Through motor earned its name because of the way the magnetic poles inside are continuously "written" on a magnetic layer in the rotor. It is this technology which enables the motor to maintain its speed. "One of the most important features of the Written-Pole Ride-Through motor is its extremely large internal rotational inertia. This property gives it the capability to 'ride-through' short-term power interruptions and deep voltage sags, which occur more often on single-phase lines than three-phase lines," Bowe explained.
The Written-Pole Ride-Through motor has three modes of operation: Start Mode, Written-Pole Mode and Run Mode. When first turned on, the motor operates in Start Mode and remains in this mode until it reaches the Written-Pole transition speed. Once stabilized at full speed, the motor switches into Run Mode. In the event of a short loss of power - up to 15 seconds - during which the speed of the motor drops to within the Written-Pole transition speed, the motor resynchronizes and operates in this mode until it has stabilized again at full speed.
By far, the biggest difference to Jensen is its worry-free operation. "My days of babysitting are over — the Written-Pole Ride-Through motor doesn't require manual restarting like an induction motor does. The motor's software automatically restarts it when intermittent outages, surges and sags last as long as 15 seconds," he said. In contrast, conventional motors have problems operating during an interruption as brief as one second.
"I knew the motor would work, but I felt - and maybe still do - a bit cautious about any problems that might come up," Jensen said. "My biggest fear is a lightning strike, but that doesn't have anything to do with changing motors."
To ensure a successful season, north central Wisconsin growers have no choice but to irrigate their crops - the region's sandy soil drains more rapidly than soil found in any other part of the state. Because Jensen's irrigation system takes three days to cover his 105 acres of corn, potatoes and soybeans, he was especially concerned about reliability.
Evaluating Jensen's current and future electrical use and analyzing his irrigation system revealed an inefficiency that needed correction - before the conversion, Jensen was using a 110 hp diesel engine when he could have gotten the job done with a 65 hp engine.
Jensen experienced a bit of a wait for his Written-Pole motor. Currently, there's only one supplier and it's located in Florida. Written-Pole motors are available in 20, 30, 40, 60 and 75 hp models.
Part of Jensen's decision to install a Written-Pole motor included the conversion from a high-pressure irrigation system to a low-pressure system. The reason? They needed to reduce the horsepower so Jensen could run a less powerful (and therefore less costly) Written-Pole motor.
First, Jensen and Bowe walked themselves through the process, trying to anticipate any potential problems associated with the location Jensen had selected.
It took a total of three days to install Jensen's Written-Pole Ride-Through motor, which is not sold with any kind of stand. In order to avoid exposing the motor to standing water, they found themselves designing and constructing a motor stand and pouring concrete to form a pad on which to mount it. Because of its size and weight, Jensen rented a crane to mount the motor onto the stand. They learned that lining up the motor shaft with the pump shaft can be a tricky process, but it must be done precisely to avoid vibration. The installation took several people and required about 20 hours of wiring time. Other challenges Bowe and Jensen faced were in properly sizing the pump and motor so the two would work together efficiently, and determining the appropriate size (hp) of the Written-Pole Ride-Through motor to match the 800 gallons-per-minute capacity of Jensen's well.
Not long after the installation was completed, they noticed that the pump was making the motor run at 115% of its capacity. An adjustment to the pump now allows him to achieve his desired water pressure and flow rate. Jensen has two pivots mounted on one pump, enabling the system to cover his acreage in three days. "There were a lot of things to think about," Bowe said, "but everything went pretty well considering this was one of the first installations of a Written-Pole Ride-Through motor in Wisconsin."
When the motor is used 800 hours annually, Jensen is saving $1,344. After spending approximately $9,000 to convert to a low-pressure irrigation system, it now costs just $1.92 per hour to run the 40 hp Written-Pole Ride-Through motor. In comparison, the 110 hp diesel engine he ran for years cost him $4.84 per hour. It consumed four gallons of fuel per hour. "I was lucky to get my supply for this season at $1.21 per gallon," Jensen said, "considering where prices ended up here in the Midwest."
The Written-Pole Ride-Through motor has a 94% efficiency rating, while a standard motor runs at about 83% efficiency and a diesel engine at about 65% to 80%.
Although costs vary from farm to farm based on the type of irrigation system, Jensen's total costs for the project were nearly $27,000 - $12,000 of which was the cost of the Written-Pole Ride-Through motor. The balance went toward other improvements that made economic sense for Jensen, including changing out the sprinkler package to accommodate conversion from a high-pressure to a low-pressure system. Jensen also attached a booster pump to one of his pivots. The total cost of the project was comparable to what he would have paid just to bring three-phase service in to his operation. In addition, with the three-phase, Jensen would have had to purchase a 60 hp motor, instead of the 40 hp Written-Pole Ride-Through motor he now runs.
"My goals were to lower my cost per hour to irrigate, and get rid of the noise and maintenance of a diesel engine," Jensen said, "and Dale and I accomplished that." He's noticed that a few cars have stopped along the road, their drivers peering out the window to take a quick look at the installation. In describing his experience with the Written-Pole Ride-Through motor, however, he doesn't focus exclusively on saving money.
In the many hours he spent with Bowe, Jensen learned about the variety of services and programs offered by Wisconsin Public Service. He was also impressed with the resources WPS provides to employees like Bowe, who are out in the field on a daily basis helping customers solve problems. When some fine-tuning became necessary, they set up Dale's computer between the service panel and the Written-Pole motor and made some quick changes that Jensen says he wouldn't have been able to do by himself.
"This thing can withstand Wisconsin's unpredictable weather, its reliability frees me up to get more work done, and other than keeping the air passages and cooling fins clear, it requires very little ongoing maintenance - what more could you want?" Jensen asked with a smile.
If you would like further information on how Written-Pole motor technology can benefit your operation, call Dale Bowe, Agricultural Account Executive, Irrigation, at 715-345-7509.