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TONY SCULPHER, REGIONAL SALES MANAGER, NORD DRIVESYSTEMS AU   

High efficiency saves on energy

As early as 1997 NORD Drivesystems developed a series of four-pole three-phase electric motors, which were considerably more efficient than contemporary electric motors.

Depending on the power of the electric motor, these NORD electric motors were up to 13 per cent more efficient than average. A further increase in efficiency was achieved by the selection of the optimum type of gear unit and the lubricant used.

As well as this, frequency inverters were consistently used, with which the speed of rotation of the gear units could be matched to changes in power requirements. This multiplied the efficiency of the individual components to bring about an overall efficiency, which could reduce energy consumption (that is, operating and energy costs) by up to 40 per cent.

These substantial savings were not simply achieved with a single product, but rather by taking an overall view, which includes the electric motor, gear system, and the drive electronics.

Skilful use of energy

To achieve energy consumption goals, we must first consider how much energy does your present drive system convert into heat, and what proportion can be recovered by modern technology. It is possible to put the energy, which the drive system generates during operation into productive use, and make savings with adjacent components. Such a drive effectively reduces the energy consumption of the entire drive system.

If the movement of machinery is often or regularly braked, it may be worthwhile using this energy. With conventionally braked electric motors, the energy released is wasted; it is dissipated into the environment via the frequency inverter and braking resistors in the form of heat.

The more effective and ecological solution is to use drives which utilise the energy generated by linking intermediate circuits or by feeding the energy back into the mains. The energy generated during braking is returned by a regeneration unit, and can be supplied to other components in the systems. This reduces the overall amount of current which needs to be supplied by the mains.

Higher efficiency with DC networks

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 which is not used by the network is fed back to the mains via a regeneration unit. With this solution, the directly used part of the generated energy is unaffected by the efficiency of the regenerative feedback unit.

In this case the regeneration unit can usually be smaller and therefore cheaper. However, DC coupling also makes sense without a regenerative feedback unit, as it is still often possible to save considerable amounts of energy.

Efficiency optimised electric motors (IE1, IE2, IE3)

In drive technology, energy saving solutions require a well thought out approach - both for the drive electronics and the mechanics. In addition to various technologies in the field of the frequency inverters, new electric motor concepts are also being developed.

In order to design units which can comply with the new IEC efficiency class IE3, NORD prefers to use copper for the rotor squirrel cage instead of aluminium. Thanks to its lower DC resistance, this material enables the construction of electric motors which are more efficient for their size.

On the other hand, with the same efficiency, the power can be increased without increasing the physical size – so that the electric motor is easier to install in confined spaces. An even greater increase in power density with very high efficiency can be achieved using an optimised synchronous electric motor with high quality permanent magnets in the rotor.

NORD manufactures and supplies such systems, as well as the necessary speed control processes. NORD electric motor development has also ensured that by skilful dimensioning of the active components and an optimum selection of the magnetic materials, the torque over the speed range is not significantly different to the usual values.

 

Pic: NORD drives technology opens up great potentials, especially in the area of partial loads.



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