Written-Pole™ Ride-Through Motor Electrical Facts

New Technology Designed Exclusively for Single-Phase Service

Whether you need to drive irrigation pumps more efficiently or power grain dryers, cranberry bog pumps or potato storage ventilators, there is a good chance that the Written-Pole Ride-Through motor can improve your bottom line and seriously cut the amount of time you spend on maintenance.

If your farm has a large electric load located far away from a three-phase distribution line, you might consider installing a Written-Pole Ride-Through motor. Your Wisconsin Public Service agricultural consultant can help you calculate your potential savings and answer questions about Written-Pole motors.

Run Remote Irrigation Loads More Economically

For the first time ever, growers with single-phase electrical service have a viable alternative to using a conventional induction motor with a phase converter or a diesel engine to power large equipment.

In Wisconsin, some irrigation sites are located several miles from the nearest three-phase line. A price tag of approximately $28,000 per mile to install three-phase distribution lines is often the reason growers decide against a conversion.

Defining and Understanding The Technology

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. Perhaps the most important feature of the Written-Pole Ride-Through motor is its extremely large internal rotational inertia.

This property gives the Written-Pole Ride-Through motor the capability to 'ride-through' short-term power interruptions and deep voltage sags.

The internal rotation inertia also extends the time required for the motor to come to a complete stop after the power is turned off.

If the motor is not loaded, it can take between 30 and 60 minutes to coast to a stop. This capability is made possible by the added weight in the rotor and its inside-out construction, which makes the motor larger and heavier than conventional motors with an equivalent rating.

Growers Reap Short- and Long-Term Savings

Wisconsin's first Written-Pole Ride-Through motor installation is saving a Waupaca grower $1,344 when the motor is used 800 hours annually. 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 contrast, the 75 hp diesel engine he ran for years cost him $4.84 per hour, using the motor 800 hours annually. It consumed four gallons per hour; the grower spent around $200 per year for routine oil and belt changes and maintenance.

A Written-Pole Ride-Through motor eliminates the inevitable diesel engine overhaul. Although diesel engines may need rebuilding only once in ten years, labor, parts and milling can cost anywhere from $6,000 to $10,000. 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%.

Withstands Even Wisconsin's Unpredictable Weather

The Written-Pole Ride-Through motor is designed to operate in ambient temperatures ranging from 32ºF to 104ºF. However, test results show that Written-Pole Ride-Through motors have reliably operated in temperatures ranging from-42ºF to 122ºF. They may be operated safely in the open air if there is adequate protection from direct rain. The motor base must be mounted on a raised concrete pad or steel frame to avoid exposure to standing water.

Significantly Cuts Maintenance Time

The Written-Pole Ride-Through motor's slower start-up means less current draw. It takes about 55 seconds to reach full speed and requires only two times its running current at start-up. A conventional induction motor starts faster, drawing about six times its full load current, which can cause fluctuations on the line and other power quality problems. A slower start-up also prevents the motor from getting as hot as it would during fast start-ups, extending the life of the motor components.

Compared to the typical diesel engine, maintaining the Written-Pole Ride-Through motor is extremely easy. The days of checking a diesel engine several times a day, maintaining belts and changing oil are over. The operator needs only to start the motor and return to shut it off.

Other than keeping the motor's air passages and cooling fins free of dirt and debris, the Written-Pole Ride-Through motor requires little ongoing maintenance with normal use. The bearings are lubricated and sealed for the life of the bearing. Although a bearing change may be required from time to time for normal reasons, it can easily be done in the field.

How the Motor Operates

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. Whenever the speed falls below the Written-Pole transition speed - due to a power interruption or electricity overload - the Written-Pole Ride-Through motor resynchronizes, or goes back into Start Mode.

Additionally, the Written-Pole Ride-Through motor doesn't require manual restarting as an induction motor does. When an outage lasts longer than 15 seconds, the motor's software automatically restarts it. The motor switches out of Written-Pole Mode into Run Mode when it reaches and stabilizes at its normal running speed. It is in Written-Pole Mode that the internal magnetic layer is continuously remagnetized - or 'written' - into a magnetic pole pattern. The Written-Pole Ride-Through motor switches into Run Mode after it has stabilized at full speed.

The Written-Pole Ride-Through motor will continue to deliver power as it winds down from either being shut off or from a loss of power. When power is restored, it will automatically resume operation in whichever mode (Start or Written-Pole) is appropriate for the speed at that moment.

The Written-Pole Ride-Through motor 'rides through' outages as long as 15 seconds, outlasting 99% of power problems such a intermittent outages, surges and sags. It continues to output 60-Hz power by creating poles at a 60-cycle rate for up to 60 seconds, even at full load. Conventional motors have problems with interruptions as brief as one second.

Motor Installation Can Be Challenging

Because of its size and weight, it will take several people to install a Written-Pole Ride-Through motor. Although installation is not a dangerous process, it's a good idea to walk through it before the motor is delivered. Every site is different; be sure to consider any potential problems associated with the future location of the motor.

Give some thought to the following items:

The pump you're operating to achieve the desired water pressure and flow rate determines the size (hp) of the Written-Pole Ride-Through motor.
The large, heavy motor must be mounted on the motor stand by a crane or a lift boom.
Lining up the motor shaft with the pump shaft must be done precisely to avoid vibration.
Designing and building the motor stand may be slightly more complicated than expected.
Get expert advice on properly sizing the pump and motor so the two will work together efficiently.

Partner With WPS

Irrigators no longer must work with less convenient methods to pump their systems. Alternative methods include the installation of a phase converter to create three-phase power (which may cause power quality problems and lower efficiency) or the installation of a gas or diesel engine (which are far less efficient). WPS is happy to assist you in planning and selecting a Written-Pole Ride-Through motor.

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