It is reckoned that 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. From these factors it is clear that investment in efficient drive technology is essential. The IEC60034-30 standard, making the IE2 energy efficiency class mandatory throughout Europe for a large number of electric motors from June this year, will begin to ensure reduced energy consumption on a global scale. Further statutory initiatives for IE3 Premium Efficiency motors will come into force in the next few years and NORD DRIVESYSTEMS has already assembled a complete 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, it is NORD DRIVESYSTEMS' view that energy saving does not stop at optimising the consumption of individual motors but 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 experience in energy saving motors and drive technologies, NORD has developed innovative efficiency 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 output frequency which is higher than that of the mains in order to increase efficiency. Motors with 230 V/ 400 V star-delta circuitry can be operated at up to 87 Hz with a 400 V inverter in a delta connection, whereby the motor can be operated at a higher speed of up to 87 Hz with the rated torque. Up to approximately 100 Hz, this increase in frequency results in an improvement in the efficiency 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 yield-ing 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
Whilst conventional frequency inverter applications discharge the braking en-ergy 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.