Efficient drive solutions complement IE2 and IE3 motors

18 October 2011

More than two thirds of the total energy spend for industrial automation is consumed by electric drive technology and that an individual electric motor’s energy consumption makes up about 98% of its total cost of ownership over its average life.

The IEC60034-30 standard, made the IE2 energy efficiency class mandatory throughout Europe for a large number of electric motors from June this year. Further statutory initiatives for IE3 Premium Efficiency motors will come into force in the next few years Nord Drivesystems has already assembled a com-plete range of IE2 and IE3 motors that bring benefits of increased efficiency, less waste, reduced greenhouse gases, increased service life and reduced operating costs.

However, the company believes that energy saving does not stop at optimising the consumption of individual motors and that practical efficiency measures and a 'green' approach should also be built into the complete drive system together with consideration for the overall application process. With many years experi-ence in energy saving motors and drive technologies, Nord has a range of effi-ciency optimised drive features that include high-frequency operation, automatic flux adjustment, energy recovery, and intermediate circuit coupling.

Increased efficiency in 87 Hz operation
An example of this is the option of operating asynchronous motors with an out-put frequency which is higher than that of the mains in order to increase effi-ciency. Motors with 230 V/ 400 V star-delta circuitry can be operated at up to 87Hz with a 400V inverter in a delta connection, whereby the motor can be op-erated at a higher speed of up to 87Hz with the rated torque. Up to approxi-mately 100Hz, this increase in frequency results in an improvement in the effi-ciency of the motor by up to 5%.

Automatic flux optimisation during partial load operation
Intelligent control is another way to save energy. For asynchronous motors, frequency inverters generally maintain the magnetic flux level required for yielding the full torque over the whole speed range, thus causing unnecessary losses during partial load operation. Nord’s SK 200E, SK 500E, and SK 700E- frequency inverters can save resources by automatically reducing magnetisa-tion when the motor is operated under partial load for potential energy savings of up to 30 %.

Regenerative braking and DC networks
While conventional frequency inverter applications discharge the braking energy as heat, more efficient and eco-friendly drives reuse this excess energy via intermediate circuits and regenerative braking, thus reducing mains power. The efficiency of a system can be increased even further, where all the drives are linked to form a DC network, the generated energy is supplied directly to other drive units. The energy not used by the network may also be fed back to the mains via a regeneration unit.

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