Measures and recommendations for efficiency improvement of electrical motors

Awareness of the efficient use of electrical energy is becoming increasingly important, both in daily life and in
industrial settings. Electric motors, which serve as the primary driving force in various applications, are the
largest consumers of electrical energy. Enhancing their efficiency not only reduces electricity consumption and
lowers costs but also decreases CO₂ emissions, contributing to a cleaner environment. The strict regulations imposed by the EU on motor manufacturers regarding efficiency classes of electric motors require a thorough evaluation of all design parameters that impact efficiency. Some key factors include the number of conductors per stator slot (slot fill factor), motor length and outer diameter, air gap length, and the replacement of aluminum in the rotor squirrel cage winding with copper, among others. Beyond design, the efficiency of electric motors also depends on operational factors such as loading conditions and cooling.Additionally, for a given application, multiple motor types may meet the drive requirements. For decades, asynchronous squirrel cage motors have dominated industries worldwide. However, the emergence of modern technologies and advanced materials, combined with the growing demand for higher efficiency, has made synchronous motors a viable alternative to traditional asynchronous squirrel cage motors. Synchronous motors can be categorized into several types, including line-start synchronous motors, permanent magnet synchronous motors with surface-mounted magnets, and permanent magnet synchronous motors with embedded magnets. This paper aims to provide recommendations for improving the efficiency of both asynchronous and synchronous motors, considering both design and operational aspects. It provides an overview of the construction details of asynchronous motors and various types of synchronous motors, while also comparing their operating characteristics. Finally, the advantages and
drawbacks of each motor type are highlighted, with concluding remarks on their respective fields of application.