For single-phase motors, research the catalogs to find the maximum efficiencies that are presently available. Most major motor manufacturers have a“high-efficiency” line of single-phase motors, so you can narrow your search to these models. The highest efficiency is found in “capacitor start” motors, followed in declining order by “split phase,” “permanent split capacitor,” and “shaded pole” motors.
Part-Load Efficiency
The part-load efficiency characteristics of motorswere covered previously. See Figuref2. If motorsoperate for long periods at reduced loads, be sure tostudy the part-load efficiency figures. Somemanufacturers offer special models that are claimed toprovide high efficiency at low loads.