It was determined that using a medium voltage motor would further reduce overall costs due to the significantly smaller diameter motor cables that it would require. "At 460 VAC, we would need very thick cables to operate the pump," explains Brent Studnicka, an Engineer with Strand Associates. "But at 2400 VAC, the current required is much lower, meaning that a smaller gauge of wire could be used." This is due to the fact that as the voltage increases, the amount of current required to perform the same amount of work decreases. "With 800 feet of cable, this resulted in a significant savings," says Brent. The 460 VAC output of the Danfoss VLT AQUA drive is wired to a stepup transformer, which brings the voltage to 2400 VAC. The output of the transformer is then fed through a sine wave filter to ensure that the waveform is exceptionally uniform, prolonging the life of the motor.
The use of a drive also minimizes equipment stress. By reducing the number of starts required of the well pump, the drive maximizes the pump motor’s longevity. Controlling the acceleration and deceleration when starting and stopping further lowers stress to the motor as well as reducing water hammer in the pipe system.
The drive will also allow the city to work on their water towers without impact to water distribution. "Right now, this pumping station is filling the gap," says Craig McDonald, Loves Park Water Department Supervisor. "But it will also allow us to bypass a tower in order to maintain it while still providing water to the people who rely on it". The VLT AQUA drive provides the flexibility to meet the needs of the community, both today and in the future.