At Emory University in Atlanta, motors on two cooling towers that had been in service for approximately 20 years were becoming a maintenance headache.

“We were eager to move away from the traditional gearing units because most of our cooling-tower-maintenance problems relate to the gearbox,” Rob Manchester, a mechanical engineer in the university's Engineering Services department, said. “It needs regular oil changes, and the drive shafts also require ongoing regular attention. It's been a burden for our maintenance staff because the units are suspended in the middle of the cooling tower, which makes them very difficult to reach. We wanted a solution that would remove all the maintenance issues.”

Tower Engineering Inc. (TEI), a Fort Worth, Texas-based designer and installer of permanent cooling towers for the commercial, industrial, and power-generation industries, recommended the RPM AC Cooling Tower Direct Drive Motor from Baldor, which TEI had just installed at Clemson University. TEI invited Manchester to visit the site to see the motor at work.

Combining the technologies of the laminated, finned-frame RPM AC motor with a permanent-magnet salient-pole-rotor design, the RPM AC Cooling Tower Direct Drive Motor can replace the right-angle gearbox and jackshaft in many conventional cooling towers. A cooling tower's fan couples directly to the motor's shaft and is controlled by Baldor's VS1 Cooling Tower Drive for optimal variable-speed performance and quiet operation.

A labyrinth bearing isolator and flinger prevents water ingress along the shaft, while condensation drains relieve any moisture that may collect inside the motor. The electrical system is manufactured using a vacuum-pressure impregnation process that ensures long motor life, even in extreme conditions.

Designed to work with the motor to provide easy cooling-tower start-ups, the VS1 Cooling Tower Drive utilizes sensorless algorithms to accomplish smooth, low-speed operation. Additionally, it supports multiple protocols.

Manchester said the new technology will aid the university's efforts to decrease energy use by 25 percent by 2015.

“We have seen the studies that show us that this technology will provide some fairly significant energy savings (50- to 60-percent savings are typical when the system can take advantage of adjustable speed/airflow to reduce overall fan motor-horsepower requirements),” Manchester said. “I'm excited about reducing the amount of energy we consume”; and because the product is low-maintenance, “we'll achieve a cost savings on two fronts.”

Information and photographs courtesy of Baldor Electric Co.
Circle 100