By Harry Broussard and Thomas A. Farr
A Pittsburgh area water utility, West View Water Authority, supplies water to 31 municipalities and over 200,000 people in western Pennsylvania. The facility was using traditional motor starters to control two 2,000 horsepower pumps to transfer water from a reservoir to the treatment facility. The pumps were continuously operating at full speed, causing significant mechanical stress, frequent water main breaks and significant maintenance expense.
And because the motors were started across the line, the massive inrush of electrical current caused high stress on the system and generated enough heat to prematurely age the rotors. Beyond that, the local electric utility was charging for the peak demand -- the 1,400 amp draw when the motors were started -- which resulted in costly energy bills.
The West View team began looking for an adjustable frequency drive solution to reduce wear and tear on motor and pump assets and lower peak demand charges. They also wanted to identify a supplier that could quickly upgrade the motor control center and minimize installation cost in the process.
West View required an adjustable frequency drive solution that could easily fit in place of the existing motor starters and seamlessly integrate into the existing control system without major modifications. Beyond size and reliability concerns, the authority sought to ensure that their facility had readily available, local support service. Given West View’s high-availability needs, the ability to have service personnel on-site within minutes was critical.
Finally, successful operation of the West View facility required constant monitoring of water tanks approaching 10 million gallons in size. This required a service team capable of providing around-the-clock monitoring as well as backup power capabilities to protect against power outages.
The West View team turned to Eaton for their medium voltage drive needs and service requirements. Eaton’s team worked with West View and its consulting engineering firm to design a solution that fit their requirements.
The authority selected the AMPGARD SC 9000E adjustable frequency drive. Designed for use at voltages from 2400V up to 4160V, at up to 5750 hp, the drive has the smallest medium voltage footprint in the industry. The compact design enabled seamless integration of two, 2000 hp adjustable frequency drives within the existing facility with minimal demolition and installation costs.
The modular roll-in/roll-out design of system’s inverter provides time and cost savings due to low mean time to repair (MTTR). A proprietary insulation system also protects the inverter components from harsh conditions typical of water/ wastewater utilities while minimizing noise pollution at the facility.
Eaton Electrical Services & Systems (EESS), with factory-trained drive service professionals located in every major city throughout the U.S., was able to meet West View’s service requirements. The EESS team provides an around-the-clock monitoring service and installed a standby generator to supply backup power.
Eaton helped to install the drives while limiting downtime, so that the facility could continue to meet its demand and pump water to its customers – without interruption.
Today, the West View water treatment plant is a highly efficient operation. The transfer pumps are now run continuously at optimal speeds, using only the power that is needed. Furthermore, the drives are protecting key process equipment by reducing the wear and tear on system pumps and motors.
“The drives allow us to operate 24 hours a day. When they are online, we have less main breaks due to trauma placed on the system and the stopping and starting of the pumps,” said Joseph Dinkel, the executive director of operations at the West View Water Authority.
“With the new system, there are no inrush problems. The motor starts very slowly. Ultimately, it will produce the exact amount of water that we want – with no wasted energy.”
The motors are started using less than 200 amps with the adjustable frequency drives - compared with 1,400 amps for the across-the-line starters. As a result, the adjustable frequency drives are generating over $30,000 per month in energy savings for the facility.
“The first month the system was online, we documented that we were saving $1,000 a day. Over three years, we’re talking over a million dollars in savings,” Dinkel said.
About the Authors: Harry Broussard is a marketing manager at Eaton Corporation. His experience in adjustable frequency drives spans low and medium voltage drives conceptual development, extensive applications experience and field sales management.
Thomas A. Farr is an application engineering manager at Eaton Corporation. He is also the Chair of the Western North Carolina IEEE PES/IAS chapter.