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 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 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 motor is easier to install in confined spaces. An even greater increase in power density with very high efficiency can be achieved by using an optimised synchronous motor with high quality permanent magnets in the rotor. NORD also supplies such systems, as well as the necessary special control processes. NORD motor development has also ensured that by skillful 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.
2. IE2-Motors | energy saving motor with aluminium in the rotor
As a result of the design differences compared with the standard motor, the energy-saving motor has several characteristics of larger machines. The starting and breakdown torque are significantly greater than with the standard version. This is due to the use of considerably more active iron, flux-optimised windings and a greater conductor cross-section of the windings. In comparison with the standard motor, the energy-saving motor with an aluminium rotor also requires stampings with lower specific core losses. For low numbers of poles and larger motors an optimisation of the fan is also necessary.
3. IE3-Motors | energy-saving motor with copper in the rotor
The specific conductivity of copper is approx. 60% greater than that of aluminium. By using copper as the conductor material for the squirrel cage instead of aluminium, rotor losses are considerably reduced. This results in the following differences compared with the aluminium motor: The slip under load, which is proportional to the rotor losses, is considerably less. The torque curve in the operating region is considerably steeper. The breakdown torque is attained with a lower slip. The staring torque, which is proportional to the rotor losses, is considerably lower. Compared to the aluminium motor, in the energy-saving motor with a copper rotor, an increase in the amount of iron is only necessary to a moderate extent, or can be dispensed with entirely. Here too, the exclusive use of copper is not sufficient. Stampings with lower specific core losses, larger conductor cross-sections in the windings and flux-optimised windings are important components of this design.