This white paper addresses the effects of motor shaft currents and solutions to the problem Cleanroom Applications Significant growth of the semiconductor industry during the last decade has led to advances in cleanroom technology. Simply put, cleanrooms are designed to eliminate airborne contamination through insulation and thoroughly filtered air. This environment improves both product quality and output. First used as surgical facilities, cleanrooms are now vital to the semiconductor, pharmaceuticals, and high-tech instrumentation industries, to name a few, and are used as research and development facilities as well. Cleanrooms keep contaminants that could cause circuits and critical equipment to fail while being manufactured, or even in production years later, out of the air.
Fans are the key components in the air handling systems of cleanrooms.
In a typical cleanroom application, hundreds of fans operate around the clock to keep air moving through the cleanroom after it has been processed by filters that remove nearly all contaminants. The fans ensure that columns of air move from the ceiling to the floor at the same speed, eliminating variations in air currents, as well as recirculating and filtering the air. Variable-speed drives produce many switching pulses that result in common mode noise. The audible noise generated by the damaged bearings is unacceptable in the cleanroom environment and motor failure soon follows. Figure 2 Common mode equivalent model.