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Focus on the overall package for optimum energy efficiency

Focus on the overall package for optimum energy efficiency

Are you considering overall energy efficiency yet? Ian Allan of ABB argues that it is important to look at the whole gamut of system components.

There have been big strides in raising the efficiency levels of individual products like electric motors, fans, pumps and variable-speed drives. In fact, from January 1st 2015, the next electric motor efficiency level, IE3, is mandatory. Meanwhile, at the 2014 Hannover Fair, manufacturers were unveiling motors with efficiency levels that hit IE4 and even an IE5, potentially allowing it to comply with the as-yet-unpublished 'ultra-premium' efficiency norm.

Yet focusing on improving the efficiencies of individual products, while important, is to miss a bigger opportunity. After all, the efficiency of individual products can only be squeezed so far, so isn't it time to look more closely at the overall efficiency of the package of components that make up, for instance, a working pump process - the pipework, valves, motors, variable-speed drives, bearings, couplings, gear-boxes and pumps?

In many ways, the tracks have already been laid down by the Energy Related Products (ErP) directive which sets out minimum efficiency grades for specific products that consume energy. For example, the efficiency grade for fans being placed on the market for the first time is based on the electrical input power and therefore encompasses both the fan efficiency and the motor efficiency. To decide whether a fan is compliant with the directive, the efficiency of the complete fan is assessed; the entire system, comprising the motor, power train including the belt drive and the impeller. But it is not just fans that are affected. The ErP directive concerns all products that consume energy and therefore includes compressors and pumps. Limits are already imposed for pumps, for example, with directive No. 641/2009.

Not so long ago, users of fan and pump systems would look to the efficiency of the individual components in the system to get the best value. Today, they are more inclined to look at the total system efficiency, an approach that is encouraged by the new legislation. This is not to say that the efficiency of individual components is irrelevant. The efficiency of the motor, the impeller and the drive system are essentially the variables that the fan or pump manufacturer has to work with. But to optimise the system's performance for energy efficiency, it is important that these components are correctly dimensioned in relation to each other. It is also essential that the fan or pump system itself is correctly selected and installed. In this respect, a huge deal of responsibility still rests with the end user.

However, there is growing collaboration between manufacturers of the component parts. An electric motor manufacturer working together with a pump maker can provide a closer integration of the pump and motor by considering the total efficiency of the system to meet the challenges ahead. Some manufacturers, like ABB, are able to provide and fully integrate all components of the drive train from one source and as such offers a matched package where everything is designed, tested and approved; not just on the product level but also throughout the life cycle of the system. Efficiency is improved at all levels, not just overall system efficiency. Having one supplier brings shorter time to market, faster track to profit while maximising productivity and reliability.

While packages are the way forward, never lose sight of the technology inroads being made by each product within the system. Take the electric motor for example. Over the past decades, the efficiency of electric motors has significantly improved. A modern 110kW four-pole motor, for instance, has 30 percent lower losses than an equivalent motor from 1980, although the two motors will look very similar on the outside.

From January 2015, only IE3 motors or IE2 motors equipped with variable-speed drive can be sold. A new class for super-efficient motors, called IE4, has also been introduced. However, the efficiency levels required for this class cannot be achieved with traditional induction motors, so this class is likely to be exclusive to new motor technologies such as the synchronous reluctance motor (SynRM).

Pump manufacturers are increasingly asking for IE3 and even IE4. IE3 motors are often adequate for systems with large and medium sized motors, where the efficiency targets can be met with traditional induction motors. In smaller systems, where efficiency improvements are difficult to achieve, it may be necessary to look at other technologies, such as permanent magnet or SynRM.

However, just because a system complies with the ErP directive doesn't mean it will always be energy efficient under all circumstances. The end user is still responsible for ensuring that the system is correctly specified, selected and installed. Frequently, an oversized system is selected as the additional cost for a slightly larger system seems small in the context. But an improperly sized system will bring additional costs for energy use and maintenance, as an oversized pump or fan may be subject to mechanical stress when working away from its best efficiency point.

So, while fan and pump manufacturers do their best to provide more efficient systems and motor manufacturers develop new technologies to make this possible, a huge deal of responsibility remains with the end user to ensure the technology is used to its best effect. It's the person paying the energy bill who needs to make an informed choice.
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