Energy savings on single-phase induction motors under light load conditions

It is estimated that electric motors consume approximately two-third of all the electric energy generated in the United States. It is also a known fact that induction motors found in residential and commercial applications are often oversized and operate well below their rated capacity. Because the efficiency of an electric motor is reduced at lighter load, numerous studies have been conducted in the past to reduce motor losses under such load conditions by either lowering the supply voltage (and in some cases, supply frequency) by means of static power converters. But some articles reported conflicting results in terms of energy savings for different duty cycles; The objective of this thesis is to determine the most efficient way to operate a number of common single-phase induction motors when operating below their horsepower ratings. To accomplish this, the following steps are taken: (A) Characterize the motors in terms of their performance (at nominal voltage) and model parameters. (B) Simulate the steady-state performance under lower voltage (by SCR control) and lower load. (C) Determine a way to smooth out both voltage and current distortion. (D) Verify the simulations with laboratory experiments; It is asserted that most efficient way to run a motor for a given load is to vary the voltage until minimum input power is achieved. However, unlike the Nola concept, the implementation of such strategy is not as simple as this requires a micro-processor with memory