Practical testing of methods for improvement of efficiency of a small induction motor

Methods for improvement of induction machine efficiency are nowadays in center of interest many researchers. It is mostly due to requirements on minimal efficiency prescribed by legislation. This article describes results of some practical attempts how to improve a small induction motor efficiency. Six motors with different modifications to efficiency improvement was made and measured. The measurement results of each of them are compared with measurement results of a motor from serial production. In case of a small induction motor, the biggest losses are Joule losses in stator winding. Therefore, the most attention is pay to these losses. But core losses and Joule losses in cage can influence efficiency in considerable way too. The tested modifications are as follow: reduction of stator winding resistance, reduction of core losses by using material with lower specific losses, core lengthening, slots shape optimization, sheets annealing after punching and cooper squirrel cage.