The optimization of fan design in totally enclosed type induction motor

Abstract

The energy efficient electric motors use less power to produce the same amount of output power, which saves energy. By saving energy, heat generation thus operating costs such cooling and maintenance can be reduced. The International Electrotechnical Commission (IEC) establishes international standards for various electrical and electronic devices and systems, including electric motors. For electric motors to be reliable and energy efficient, they must comply with IEC safety, performance and environmental requirements. In 2017, IEC conducted a study on energy efficiency levels for three-phase asynchronous motors covering both two- and four-pole motors with nominal output powers ranging from 0.75 kW to 375 kW, aiming to increase energy efficiency and reduce greenhouse gas emissions. According to this study, by increasing motor efficiency, it is planned to gain 10 TWh until 2030. There are several losses degrading efficiency, though. The most important losses affecting the efficiency of electric motors are stator, rotor, copper and friction losses, most of which occur as heat. Fan designs play an important role in the efficiency of electric motors and the amount of copper used. While cooling performance increases with an efficient fan design, the amount of copper used is reduced therefore resulting in cost improvements. The main purpose of this study is to examine the effects of the design parameters of a radial bladed fan on the motor efficiency in a selected frame for a defined load and to optimize the design. The parametric analysis was carried out with the computational fluid dynamics method to examine the thermal performance with a 132 frame body with a power of 7.5 kW in the WAT Motor Company. ANSYS Design Modeler was used for the parametric drawing of the fan geometry, ANSYS Mesh was used for meshing and ANSYS Fluent was used as the solver. The optimization of the design was carried out in the ANSYS Design Exploration program according to the values of the mathematical expressions written in Fluent. The validated study was performed with a commercial fan. According to the results of this study, it was observed that the optimum fan design increased the efficiency by 8% compared to the original fan and reduced winding temperature by 8 °C while keeping the current motor's IEC efficiency constant.