Energy Efficiency in Electric Motors

Abstract

Electric motors are electrical machines that convert electrical energy into mechanical energy to perform useful work. In general, electric motors have three main parts: a rotor, a stator, and a commutator. These three parts use the attractive and repulsive forces of electromagnetism, causing the motor to spin continually so long as it receives a steady flow of electric current. These main parts also comprise other parts that transmit electric current (windings, etc.), parts that transmit magnetic flux, and parts of construction (bearings, etc.). In order to increase energy efficiency in electric motor systems, attention should be paid to the following such as motor selection, power quality, motor control systems (variable speed drive), power transmission systems equipment (fan, pump, compressor, etc.), system and design, process type, and maintenance are all the topics that need to be considered in order to increase energy efficiency in systems using electric motors.Although standard motors operate efficiently, with typical efficiencies ranging between 80 and 90%, energy-efficient motors perform considerably better. It is possible to reach 10% energy efficiency with the use of high-efficiency motors. According to the needs, the correct sizing of the electric motors must be made, the motor efficiency reaches the maximum level at 75–80% load. Synchronous motor use in applications below 11 kW saves up to 30%. Running the engine under low load causes overheating. It shortens the engine life. The power and the duration of use should be considered together in the engine replacement. In addition to all these, the efficiency of the motor alone is not enough. Together with the system to be used, the efficiency of the total system should be considered.In the design of high-efficiency motors, in addition to the use of more copper in the winding, the use of more steel in the body design, the use of thinner steel laminates on the body, more efficient rotor design, reduction of friction, and additional losses, optimum air gap between the rotor and the stator should be also considered.