Abbreviations
DRIVES, MOTORS + SWITCHGEAR
of 0,75 to 375 kW. Motors controlled by frequency converters are
exempt from this regulation. For such motors, IE2 is sufficient.
Proving the point of PMSM
The improved performance of a PMSM translates into a lower total
cost of ownership, a reduction in CO
2
emissions and ongoing sav-
ings that help to protect against future increases in energy costs.
This improved technology and efficiency translates into a higher
initial purchase cost which is later recovered during the operation
life of the PMSM. In order to provide supporting evidence of this,
the company that the author represents, agreed to participate in a
direct comparison where an inverter driven Asynchronous Motor
(ASM) and a permanent magnet motor were set up to perform
identical tasks. The comparison was conducted on an operational
waste water treatment plant in Germany with bothmotors powering
a disc thickener for seven hours every day.
The same frequency inverter, which was programmed to moni-
tor the loads on each motor, was used to ensure that they ran at
optimum efficiency. To be certain that any differences in efficiency
could only be attributed to the motors, each drive system used the
same gearbox. Having completed the exact same task, the results
are shown in the table below:
Torque
(Nm)
Speed
(RPM)
% Effi-
ciency
Energy
Consumption
(kW/hr)
Four year
Consumption
(kW)
ASM 2,62 1 350 61,5
0,26
2 657
PMSM 3,50 1 500 87,7
0,16
1 635
The trial demonstrated that the PMSM delivered a 40% saving in
energy consumption against the ASM, which, when projected over a
four year period, would have saved 1,022 kW. As the price of energy
continues to rise, so the value of this saving will increase.
Drivetrain design
The design of modern drivetrains requires specialist knowledge
and expertise in order to produce a product which will not only
meet the specifications but also deliver efficiency, smoothness and
low noise qualities as well as excellent reliability. However, further
benefits of a good design can be gained by ensuring the drivetrain is
properly integrated into the application, which requires an in-depth
understanding of the given industry.
Less efficient designs such as worm geared motors can be re-
placed with integral helical bevel geared motors, which are much
more efficient and provide a longer service life. This approach
ASM – Asynchronous Motor
EPDM – Ethylene Propylene Terpolymer
PMSM – Permanent Magnet Synchronous Motor
By looking at the bigger picture and combining the
best technology from individual areas, it is possible to
achieve significant savings and efficiencies.
