03. April 2014

Energy-efficient with reduced mass and losses
Presented at the HANNOVER FAIR 2014: PM motors from VEM continue to demonstrate their benefits with a new generationof frequency converters.

The tighter statutory requirements relating to efficiency classification must not necessarily lead to motors becoming larger. VEM is taking a different route to enhanced energy efficiency.

The problem:

The use of variable-speed drives seems certain to increase in the next few years. After all, they are a proven means to implement better and more economical control in technical processes. According to CMEP estimates, around 50% of all electric motors will be operated on a frequency converter by 2020.

Against this background, selection of the most suitable motor is becoming ever more important. EFF2 asynchronous motors have been the preferred choice since 2000. In accordance with EU regulation 640/2009/EC, however, the distribution of mains-operated IE1 motors has been forbidden in Europe since 16th June 2011. From 2015, mains-operated asynchronous motors with outputs >7.5 kW – and from 2017 also those with lesser outputs – must comply with energy efficiency class IE3.

Already from 2012 and 2013, therefore, IE2 asynchronous motors with enhanced efficiency have often been ordered also for compact drives. The particularly elegant design with the converter mounted directly on the motor offers the user a simple and reliable solution for variable-speed drives. Decisive benefits are achieved with regard to purchasing, installation, commissioning and not least service.

The stricter efficiency requirements necessitate considerable efforts on the part of the manufacturers to design motors in accordance with the IEC shaft heights and dimensions. This is usually accomplished by using better sheet metal qualities and by increasing the motor volume right up to the permissible maximum.

The solution:

To counter this trend, VEM has already been manufacturing permanent-magnet synchronous motors (PM motors) for several years. These motors can be assigned to energy efficiency class IE4. The advantages of a significantly lower mass and reduced power losses form the basis for resource-sparing and energy-efficient drive solutions. The lower mass moment of inertia of the rotor compared to IE3 asynchronous motors is combined with the high dynamic response of a PM motor and the very good efficiency both at full load and in the partial load range.

The difference to an asynchronous machine becomes even more evident from the comparison of an IE4-K11R112M2 asynchronous motor with a PM machine for the same output. The IE4 asynchronous motor weighs 59 kg and thus almost twice as much as the PM motor with 30 kg. The equivalent IE3 motor can be realised at a weight of 46 kg.

The converter manufacturers have also reacted accordingly. Danfoss, for example, offers a new generation of frequency converters (FCP106) which can control both asynchronous and PM motors. The new series of compact drives with the designation MPE2R…DAN, which incorporates the new converter, will be available for outputs up to 7.5 kW in 2014, and up to 22 kW in 2015.


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