Training course on energy efficiency in SMEs - engine-sme.eu

7. Motor sizing
Motors may be driven much higher, lower or
more variable than for which they were first
specified – and this causes losses. It may not
always be economically feasible to simply
buy a replacement motor for the sole reason
of higher motor efficiency, however, when
they need repairing it is strongly
recommended not to repair these motors but
to buy high efficiency ones.
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In practice most
motors are only
65% loaded
However, the first step in performance optimisation is the characterisation of the
process load to determine its magnitude, duration and variability by hour and
season. In the next step the motor size will be adjusted to the requirements.
Modern motors are generally designed for maximum efficiency at 75 per cent full
load. Between 50-100 per cent load there is only a small variation in motor
efficiency.