There are clear financial and environmental benefits to reducing the TCO of a motor. While each application will vary, there are several factors which can go some way to achieving beneficial reductions.
1 - Variable Speed Drives
In many motor-driven systems, the motor will be over powered for the task it performs. This excess output may be managed with the addition dampers or throttling valves. While these approaches may achieve the required output, they can unnecessarily waste energy and have other adverse side effects, such as shortening a motor’s life.
While many modern VSDs incorporate functions specific to their application, their primary function is to moderate the energy input to a motor to match the required output. Adding one to a motor-driven system can deliver significant energy cost savings and improve the motor’s operation life. Other benefits include improved process control, managed start-up and stop procedures, and power quality management.
The potential energy savings achievable by adding a VSD will depend on various factors such as the application, the motor’s specification and the duty required. If, through the introduction of a VSD, the motor’s speed can be reduced by 20%, energy savings of 50% will be made. But as an example, in many cases, motor- driven pumps and fans will be over- specified for the task they are performing.
2 - Improved efficiency motors
In the majority of cases, the efficiency of a motor is classified by an International Efficiency or IE rating. Four classes are defined in the IEC 60034-30-1 standard, covering 2, 4, 6, or 8 pole motors with rated outputs from 0.12kW to 1000kW and rated voltages from 50V to 1000V. IE1 is Standard Efficiency, IE2 is High Efficiency, IE3 is Premium Efficiency, and IE4 is Super-premium Efficiency. Many motor manufacturers also produce motors that meet the IE5 class, labelled Ultra- premium Efficiency, which, while currently outside the IEC standard, is due to be incorporated in the next revision.
Across the world, legislation is in place to govern the energy efficiency credentials of new motors being put into service, as outlined in the AEMT’s Eco Design Regulations for Electric Motors Guide. However, this does not cover motors which have already been put into service.
Many motors in service are low- efficiency models, some manufactured before the first IE rating was introduced. As energy losses are reduced by around 20% or even more between each class, replacing an older, less efficient motor with a new model, one, two or even three classes more efficient, offers the potential for significant energy cost savings.
Many AEMT members can carry out energy audits on your existing systems to help you understand the savings that can be made through the addition of VSDs or by replacing lower-efficiency motors with a higher-efficiency model.