Case study of using multidisciplinary techniques to redesign electric motors

Re-designing an electric motor by using higher quantities and/or quality of active materials (reducing as a consequence the motor losses) is a basic method used in product development activities. As a result, the motor cost could become prohibitive. Millions of swimming pool motors (SPM) are running without electricity consumption being scrutinized (EC\´s efficiency grading system bands starts from 1.1 kW). Swimming pool unit is attracting the owner attention only when it fails. In about 65...75% of failures, motor replacement criterion is preferred, decision being based on initial investment. However, besides increased values of efficiency, the market trend is more orientated towards longer lifetime trouble free expectation at competitive prices. Paper presents a case study of redesigning a standard 1 HP TEFC swimming pool motor (SPM) performing standard efficiency values ("EFF 3"Class - EU) with unsatisfactory failure rates. Multidisciplinary techniques including "fault tree" method, heat flux transfer assessment, essentials of application engineering, specific designs and tests have been correlated to detect the "weak points" and to redesign to a product with improved performances at competitive price. New motors perform 14 % to 16% higher efficiency with better power factor and higher life expectancy, Another outcome of the design was reduced manufacturing costs enabling competitive price and business sustainability for a previously disadvantaged community in South Africa. In-house dynamometer, endurance tests and site tests validated the design. Currently, the product is part of a patented series of SPMs.