Industrial Electric Motor Energy Efficiency Under Testing and Practical Conditions

Electric motors are the most important type of electric loads. They are used in all sectors and in a wide range of applications. Electric motor systems are widely used to fans, pumps, blowers, air compressors, refrigeration compressors, conveyers, machinery, home appliances and many other types of equipment. Electric motors account for more than two-thirds of all the electrical energy consumed by industrial applications. As motors are the largest users of electricity, even small efficiency improvements will produce very large energy savings. However, these improvements have also assumed an environmental role to reduce greenhouse emissions. About 90% of the total motor electricity consumption is done by AC three phase induction motors in the power range from 0.75 kW to 750 kW. There is a need to assess the efficiency of motors. Different standards are used in the world, mainly IEC 34-2 and new IEC 61972, IEEE 112 Method B and JEC 37. These standards represent certain methods to determine efficiency of electric motors in a laboratory. Efficiency is therefore an important attribute, but the nominal efficiency alone is not sufficient to actually evaluate the energy consumption of an electric motor under real conditions. Generally, the electric motors are operated under different load conditions, different operating temperatures and different electrical supply conditions such as line supply voltage fluctuations, voltage unbalance and voltage harmonics. All these parameters have an impact on the efficiency of the motor. Unlike testing motor in a laboratory, the methods given in the standards cannot be used for motor efficiency evaluations in the site. For example, it is difficult to load a motor in the field with a dynamometer when the motor is already coupled to driven equipment. This paper represents the basic methods to evaluate the efficiency of electric motor under testing and practical conditions. And finally some electric motor efficiency evaluation results from some Iranian industrial plants inventories are represented.

کلیدواژه ها:

Electric motor ، Efficiency ، Energy Saving ، Test Methods ، Practical Conditions