Probing for the Energy-Conserving Load Rates of the Asynchronous Motor by Harnessing the Efficiency and Power Factor Synergy

Abstract

In the light of the energy saving drive and environmental concerns in today’s world, the technical and procurement staff of industries are encouraged to invariably take into consideration, motor efficiency as well as power factor in their motor load analyses prior to embarking on motor installation/replacement decisions. It is believed that with this practice, which hinges on a tradeoff between loading at high operating power factor and loading at high operating efficiency, the motor-driven business may stand a better chance of being run greener and more economical. This article proposes a method that engineers in research or in charge of the operations and maintenance of the 3-phase squirrel cage induction motor (SCIM) in business, may deploy to arrive at the energy efficient load range/rates for the machines of interest. The method was developed with the aid of the following motor curves viz: the load/efficiency curve, the load/compensated power factor curve as well as the load/kilovolt ampere reactive (KVAR) curve; and demonstrated on three different SCIM ratings, to determine their respective most energy efficient bounds of loading. Field data, z-score analysis and the power loss simulations were used for validating the proposed method. The energy efficient load range/rate was found to be machine-specific and the width of this load range seemed to be jointly governed by the high efficiency span of the load-efficiency curve as well as the load-wide profile of the power factor over the most part of the SCIM loading, up to full load. The mean optimal loading for the machines investigated, ranged from 66% - 73%, with standard deviations not exceeding 15.85%.