There are conflicting opinions on the harms and benefits of oversizing motors. According to a survey taken by Automation World, there are a number of reasons why around half of the responders continue to oversize despite the energy concerns. The most popular reason was to make up for variations in system operations, while some other reasons were based on taking preventative measures. Many feel that it is better to be safe than sorry and others think that the price of a larger motor is easier to handle than the price of a mechanical mishap.
Those who don’t oversize also have a number of reasons for their choice. As manufacturers gain more knowledge about motors and systems, it is easier to more accurately determine the necessary power for the individual situation. From there, more appropriate motors can reduce energy use and subsequently the cost of operation. Progress in system flexibility also allow companies to eliminate the need for so many safety nets in the form of oversized motors.
Higher Operating Costs
When it comes down to it, the pros and cons of oversizing cannot be generalized. There are different concerns and characteristics that determine whether or not oversizing is beneficial for specific systems. However, using an oversized motor will universally have higher operating costs. If a more powerful motor is a safety net, then energy is being wasted for the majority of its use. Plus, looking at the actual mechanics of the system, oversizing can be harmful. When the rest of the system isn’t built to handle the extra power, it can create strain and a shorter lifespan for other parts. Updating other parts of the system can create safety measures that are cheaper and more efficient than oversizing.
Is It Worth It?
Oversizing can also compensate for lack of maintenance. When motors are not kept up, a motor with a higher power to begin with can run longer under the same conditions. The extra cost and use of energy isn’t worth it when deterioration due to neglect is easily preventable.
Knowing your system is the best way to avoid the need to oversize. Understanding the torque, load, speed, etc. of your system is crucial. Instead of oversizing, other preventative measures can be put into place that don’t hurt the efficiency as much. A motor runs most efficiently at around 80% load, but an over-sized motor isn’t reaching that load most of the time, if ever. It could be argued that over-sizing is needed to make up for variations in the actual operation versus the calculations of the system, but studying and understanding individual needs narrows the margin for error.
