Fans, blowers and other funny loads are addressend, along with RMS Horsepower loading.

Slow speed operation of fan systems within the air handling industry is generally performed due to two reasons: a coast down operation is required for hot (induced draft) fans to cool down before shutdown (often by using a turning gear), and operational efficiency improvements can be achieved during non-peak periods by slow speed operation using a VFD. In either case, when these fans are supported by hydrodynamic bearings, it is the oil film thickness developed from the bearing-shaft interaction that limits the minimum speed that can be maintained without causing premature wear and bearing failure. This paper will present a brief overview of lubrication theory and critical design parameters to achieve slow speed operation.

The Baldor Reliance RPM AC Cooling Tower Direct Drive Motor is designed exclusively for the cooling tower industry. This motor combines the technologies of the power-dense, laminated frame RPM AC motor with high performance, permanent magnet salient pole rotor designs.