Variable frequency drives (VFDs) are increasingly the norm in heating, ventilation, and air conditioning (HVAC) applications. These inverters reduce energy consumption by allowing motors to run at lower speeds. While yielding potential energy savings of 30%, VFDs introduce electrical currents which can shorten motor life if not properly addressed. VFDs provide such savings because HVAC fans and pumps run continuously at reduced loads. Reducing a fan’s speed by half cuts horsepower requirements to one-eighth. For this reason, VFDs represent a superior solution to the traditional throttling mechanisms used in such applications.
Most of today’s HVAC motors are built with sealed bearings. As a result, the primary cause of bearing failure in VFD-controlled motors is electrical damage. This damage occurs because voltages build up on the shaft and then discharge in short bursts along the path of least resistance–through the bearings. Over time, this discharge can lead to pitting and fluting. The National Electrical Manufacturers Association (NEMA) officially recommends bearing insulation to address these problems. AEGIS Bearing Protection Rings provide a maintenance-free solution to bearing insulation in HVAC applications. Two rows of conductive microfibers lining the entire inner circumference of the ring provide safe avenues for discharge. Additionally, AEGIS rings qualify as sustainable technology under the Federal Energy Management Program.
AEGIS Rings are already widely used in a variety of HVAC installations. Electro Static Technology (EST), the manufacturers of AEGIS rings, recently ran a test on a rooftop air conditioning unit to demonstrate their effectiveness. Running the unit at the same conditions, peak-to-peak discharges from the shaft totaled 44.8 volts without an AEGIS ring. AEGIS ring installation reduced this reading to 3.76 volts peak-to-peak, well below levels that would damage bearings. A Chicago hospital recently observed the same results after introducing AEGIS rings to an air handling unit for operating rooms.
All VFD-driven motors are vulnerable to electrical damage. As VFD-driven motors continue to grow in HVAC applications, the AEGIS Bearing Protection Ring provides a compelling solution to mitigate the risk of bearing damage through electrical discharge. Motors protected by AEGIS rings will both enjoy reduced energy consumption and reduced maintenance costs. For more information about this sustainable, cost-saving solution, including the two effectiveness tests mentioned above, consult the following white paper.