“Energy efficiency” seems to be the buzz phrase in the industry in the last few years. What is energy efficiency? What criteria are used to comprehensively compare all supposedly “energy efficient” gearmotors?

Unfortunately, energy efficiency is subjective; what is efficient in one company or in one application will undoubtedly be inefficient in another application, even if the specifications are similar. Admittedly, energy efficient motors can have multiple layers of benefits, including protection of valuable environmental resources and fund reallocation from energy bills to other areas of the company. In battery-powered applications higher efficiency will also result in longer battery life.

Though the electric car, flex fuel and other energy efficiency trends are happening with large motors/gearmotors in the automotive industry, energy efficient products are not limited to high horsepower motors in the automotive sector. A need exists for energy efficient, fractional horsepower motors/gearmotors in a number of other applications such as power drills, conveyor systems and commercial ovens.

One should not make the mistake of assuming that just because a motor or gearmotor is marked “energy efficient” in the specs or on the label that it is the best choice for a particular application. It is now more common for most end products to be “energy efficient” but in order for the end product to be truly efficient the motor or gearmotor itself must also be efficient. That means other factors, such as the size of a gearmotor, AC versus DC power and gearbox type may be more important. (Note: Because gearmotors make use of gears for speed reduction, they are sometimes able to provide much more torque then their size suggests).

Often, efficiency is only thought of in terms of energy cost savings, but initial product purchase price is should be considered when evaluating the efficiency of different devices. Consider the increased system cost related to powering a low efficiency motor. Just about every component of an electrical system must be sized based on current draw and typically less efficient devices require a higher current carrying capacity. Higher current means heavier gauge wires to the motor, larger relays, etc. Typically when you’re designing an application you calculate the motor’s input power based on what you need it to “do” in terms of output power. Unfortunately, many designers fail to take the next step, which is to calculate the electrical energy needed to drive the motor. This can be done using the following simple equation:

Efficiency = Output Power / Input Power

You’ll want to complete the above equation to ensure that your power supply is sufficient for your application. This will also give you an idea of how efficient the motor or gearmotor needs to be. If you have an application that will barely provide enough power to your motor, then you will need to pay special attention to the motor’s efficiency at all load conditions to ensure a successful project.

Need some help determining efficiency? Download Groschopp’s free STP (Speed, Torque, Power) calculator. This easy-to-use program allows you to enter your specifications and will calculate the efficiency of the motor or gearmotor for you.

>> Read the next post in the Energy Efficiency series.