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High Efficiency Motors

What are high efficiency motors (HEMs)?
Using high efficiency motors
High efficiency motor tips

What are high efficiency motors?

The running cost of a motor can be several times the initial outlay, so it’s important to select an energy efficient motor.

Although there’s no formal definition for a high efficiency motor these units are generally classified as motors where losses have been reduced to the absolute minimum.

Interestingly, motor losses are independent of where – and for what – the motor is used. This means that high efficiency motors can be used almost anywhere.

Using high efficiency motors

In Australia, it is estimated that three-phase electric motors account for up to 40% of the total electricity consumed in the commercial and industrial sectors.

Using HEMs offer the following benefits:

• They reduce your firm's operating costs and improve your bottom line
• Using a high efficiency motor instead of a standard motor can result in significant savings over the life of the motor
• Depending on motor operating hours, the premium in price for a high efficiency motor over a standard unit can generally be recovered in less than two years
• They are readily available in Australia
• They tend to be quieter and cooler

High efficiency motors can lead to big savings

After surveying its motors, a Perth company found that they could make substantial savings by gradually replacing them with high efficiency motors (HEMs). Their new purchasing policy is to consider high efficiency motors as new or replacement motors.

Project description

The following graph is taken from the HEMs study. It has been adapted for typical small business electricity costs. Based on a motor life of ten years, it illustrates the payback period for a range of motors and running hours. The payback period is based on the incremental cost of buying high efficiency motors in lieu of standard motors.

Figure 1: Simple payback of incremental cost of replacing a standard motor with a high efficiency motor.

Based on the above graph it makes sense for this business to incrementally replace almost all of its motors with high efficiency motors. This would be done over a number of years, as the savings do not justify replacement of a working motor.

Summary

Note: Whilst care has been taken in the preparation of this material, it is intended to provide a general idea about what can be achieved in a particular situation. Quantitative indicators may vary with time and changing circumstances. Each situation is different, requiring its own evaluation; and therefore the results given above should not be taken as being directly transferable to other circumstances. Names and addresses have been withheld for privacy reasons.

High efficiency motors - tips

Ensure your motors are not 'oversized'

Motors operate at their highest efficiency between about 60% and 100% of their full-rated load, dropping off sharply in efficiency below 50% loading. About one-third of motors in the field are so oversized that they operate below 50% of rated load most of the time. Oversized motors not only operate inefficiently, but they also carry a higher first cost than appropriately-sized units. They can also contribute to reduced power factor, which may increase your electricity costs.

When buying new motors

Ask whether high efficiency motors (especially motors that operate for more than 3,000 hours each year) can be fitted to the equipment you are about to order. Also, request efficiency figures and price premium from the supplier.

Tips on replacing standard motors with high efficiency motors

• For centrifugal pump and fan applications, make sure that the speed of the high efficiency motor is identical to the motor it will replace. Higher speeds can cause a net increase in the consumption, especially for flow applications.
• Unless the motor operating hours are high (eg. over 3,000 hours per year), it may not be economical to replace operating standard efficiency motors (which have not yet been re-wound) with high efficiency motors
• Motors that are lightly loaded or infrequently used (eg. control valve drives) may not consume enough electricity to make installing a high efficiency motor cost-effective

Further information

Find out how to reduce your energy costs, by contacting Synergy's Energy Consultants. Just email us at  energyreview@synergyenergy.com.au or call 1300 859 333.

For more information on energy efficiency in your business visit the Sustainable Energy Development Office at http://www1.sedo.energy.wa.gov.au