Repercussions of the ErP Directive
The introduction of ErP directive has brought a focus on electric motors to the fore, but that is not enough. To optimise efficiency, switchgear also has to be considered, says Stuart Greenwood of Eaton Electrical.
In the UK electric motors are estimated to account for two-thirds of industrial electricity consumption. However, according to Gambica, if variable speed control was added to the motors of relevant applications which are not currently using it, savings of around 25,000GWh of energy could be achieved, with a corresponding reduction in CO2 emissions.
This is the goal of the EU energy related products (ErP) directive. Within this context, the commission regulation for motors 640/2009/EC prescribes minimum efficiency classes for 3-phase low-voltage induction motors. The first stage of the regulation, which stipulates efficiency class IE2 as the minimum for new motors, took effect in mid-2011. As of January 2015, machinery and system manufacturers using new motors with a rated output power between 7.5 and 375kW are required to achieve at least efficiency class IE3. IE2 motors may be used as an alternative, but only in combination with variable speed control. From 1 January 2017 this will also apply to motors rated at 750W or more.
Machine manufacturers are faced with the challenge of having to redesign the systems that they are shipping today and that are not yet equipped with IE3 motors or variable speed drives. However, simply replacing IE2 motors with IE3 motors is not enough to make machines and systems more energy efficient. To ensure safe and reliable operation, the entire drive system must be analysed and the effects of design changes on the application must be considered.
To improve the energy efficiency of electric motors, manufacturers have altered the designs of their products. These alterations also affect the electrical profile, resulting in higher starting currents for high-efficiency motors. This situation also impacts on protection devices and switchgear. Possible consequences include unwanted shutdown due to circuit breaker tripping from higher starting currents or contact bounce due to higher current levels leading to contact burning and reduced lifetime or even contact welding in the worst case.
Eaton has studied the behaviour of motor protection devices in detail in practical tests. As part of this study, the DIL series of contactors and the PKZ and PKE series of motor protection circuit breakers were checked for compatibility with IE3 motors from various well-known manufacturers and improved as necessary. The results showed that the values stated in the currently applicable standard for motor starters (EN 60947-4-1) are not valid in practice for IE3 motors. Work on a draft amendment to update the standard is in progress. Eaton's current 'IE3 ready' product families ensure reliable operation of both IE2 and IE3 motors.
Selecting the right products is only part of the answer to meet the requirements of the ErP directive. It is also necessary to analyse entire processes and systems in order to comply with the required minimum efficiency levels. Regulations regarding pumps and fans also play a role as with conventional mechanical flow regulation devices, such as valves or dampers, it is often difficult to meet efficiency requirements.
Variable speed control is usually necessary to reduce losses. However, a variable speed drive is often functional overkill. Up until now, the only alternative available to designers for driving electric motors has been motor starters. Although they have the advantage of being easy to use, their functionality is limited. For applications involving fixed speeds or low operating cycles, motor starters in combination with IE3 motors are still the most energy-efficient solution. However, if the aim is to improve the energy efficiency of existing systems that run at constant speed but less than full rated load, there is now a third option in the form of variable speed starters. Bridging the gap between motor starters and variable speed drives, Eaton's DE-1 variable speed starter is as easy to use and as reliable as a conventional motor starter, with the added advantage of variable speed control.
With solutions such as variable speed starters and IE3-ready switchgear, Eaton helps machine and system builders implement more simplified, compact and lower-cost machines and systems that are more reliable, safer and energy-efficient.
Other News from Eaton Electrical
Latest news about Electrical components