Efficiency confusion

26 October 2010

New international standards for measuring and categorising efficiency of low voltage motors are now in place. Steve Ruddell, division manager of discrete automation and motion at ABB, argues for more clarity in the marketplace.

Out go European efficiency categories Eff1, Eff2 and Eff3. In come IE3, IE2 and IE1. In the near future, we will see a new breed of super-efficient motors, IE4. The new testing standard and classification system will make for a fairer, more accurate comparison between motors and provides a level playing field for motor manufacturers.

The new grading standard has no special logo, however, the efficiency classes will be clearly specified on the rating plates of the motors as well as on the motors’ documentation. From June 2011 onwards, manufacturers are not allowed to market IE1 motors, although customers will still be allowed to install remaining stock. Then from January 1, 2015, the legally specified minimum efficiency IE3 must be maintained for power ratings from 7.5 kW to 375 kW (from January 1, 2017, the power band is being lowered to 0.75 kW). As an alternative, an IE2 motor together with a variable speed drive (VSD) must be used.

But does the legislation actually go far enough? ATEX motors, for example, are excluded. Such motors account for some ten per cent of the total installed based and are used in continuous processes often found in chemical, oil and gas. These motors consume vast amounts of energy simply by the 24 hour, 365 day nature of the processes so while accounting for ten per cent of the installed based, they account for more than ten per cent of energy consumption. And for that reason I would have liked to see them included.

Furthermore, the legislation stops at 375 kW. Although motors rated >355 kW represent only 0.3 per cent of the installed base in terms of numbers, they consume more than 29 per cent of the total motor energy bill. Why omit powers above 375 kW?

Clearly large motors are inherently more efficient than smaller motors but without a detailed benchmark then how does a customer actually know that they are buying a high efficiency, higher power motor. In theory, the door is open for unscrupulous manufacturers to claim any motor rated greater than 375 kW is high efficiency without needing to meet any minimum efficiency standards.

The majority of the installed motors base has a lifecycle of between 10 to 30 years. So how do you go about ensuring that the installed base conforms to IE2/IE3 within a sufficient timescale? When the ATEX directive was introduced there was a window in which end-users needed to ensure that all their installed motors would meet the legislation. Such a window is missing within the proposed efficiency legislation. So long as the motors have been put into operation prior to the legislation taking effect then they do not have to meet the minimum efficiency standards.

So in effect, the end-user does not need to do anything until the motor fails. Then they have the normal choice between rewind or replace. If the motor is sent for rewind, then the repairer is not compelled to rewind to meet the latest minimum efficiency standards in force. Even if they would like to then the motor may be physically too small to accommodate the increased active material needed to attain the higher levels of efficiency stipulated for IE2 and IE3.

So if the guidelines allow the motor to be rewound then it will take an eternity to get the market harmonized to the new efficiency levels, thus extensively prolonging the ultimate aim of reducing carbon dioxide emissions.

Finally, what happens if manufacturers outside of Europe decide to ship motors that do not conform to the EU legislation into our market? It is not clear how the legislation will be enforced. Who will carry out the enforcement? How will it be carried out? What will be the penalty for those failing to comply?

If there is a risk of this happening then it is important to ensure there is a severe enough punishment in place to act as a deterrent. But what is this deterrent: a fine or suspension of that motor from the market? A decision needs to be taken to clarify this situation for motor manufacturers and end-users alike.

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