take note
removes the need for a coupling and bearing thereby providing near
perfect transmission efficiency. In some cases it can be beneficial to
streamline this process and specify a bespoke solution, which can
be built from existing components but integrated seamlessly into
the machine and thereby delivering the best possible solution. By
involving designers at the outset of a project, greater efficiencies can
be gained, both in terms of cost and energy.
Drive couplings
Forming a crucial link between the electric motor and driveshaft,
the coupling can have a significant influence on the performance of
the equipment. Depending on the application, maintenance require-
ments and torque specification, the design of the coupling should be
carefully scrutinised to ensure reliable performance as well as ease
of maintenance. Specifying a coupling incorrectly can lead to inef-
ficient power transmission as well as increased maintenance costs.
Couplings are designed to accommodate shaft misalignment,
which may be present when one of the connected shafts is located
by a self-aligning bearing, or when an unsupported, intermediate
shaft is placed between the driver and the load. Couplings capable of
overcoming true angular misalignment include the single universal
joint with its capacity to handle large offsets and torsional damping.
If both shafts are assembled in self-aligning bearings then zero
misalignment can be achieved, allowing the use of a solid coupling
which simply supports the shaft in perfect alignment. Before install-
ing a solid coupling, an interesting test is to try a flexible coupling
first. With the machine at normal operating temperature, measure
the speed or the current drawn by the motor. The difference between
these readings and those with the solid coupling indicate the losses
generated by the flexible coupling. This demonstrates the extra sav-
ings that can be made by spending some additional time attaining
proper shaft alignment. The basic construction of flexible couplings
consists of two flanges or hubs, which attach to the shafts being
coupled and a connecting element that may be metallic, such as in
disc couplings; it may also be a sleeve made from elastomeric mate-
rial, such as EPDM rubber, neoprene, Hytrel or urethane, or it may
be mechanical as in a u-joint or gear coupling.
DRIVES, MOTORS + SWITCHGEAR
Markus Kutny has worked for Bauer Gear Motor GmbH
since 2009. Having worked as a field sales engineer for
two years, he has specialised in energy efficient drive
technology with permanent magnet synchronous motors,
for which he is the global manager for Bauer.
Enquiries: Email
Figure 1: In terms of overall efficiency within drive systems
which are powered by electric motors, the mechanical system
also needs to be considered as it possesses a very significant
potential for optimisation.
Figure 2: By examining each component within this mechanical section and
optimising the design, further efficiencies and savings can be made.
Conclusion
Looking at each of the aspects discussed provides an insight into the
potential energy savings that can be made in the individual aspects of
drivetrain design. Combining these efficiencies into one application
can yield impressive results, which can be further enhanced when the
overall design is undertaken by a single, specialist manufacturer. In
this way, each of the components is matched and designed to operate
with the others, while also providing a single point of contact for any
training or maintenance issues. Examining the mechanical efficien-
cies, and making significant improvements in this one area, can result
in a reduction in overall power requirement from the electric motor.
By installing a smaller motor, which is connected to a more efficient
mechanical drive, the overall effect is to reduce energy consumption
and improve reliability by using matched components.
When specifying drive systems for applications with tough en-
vironments it is important to speak to a solutions provider with the
experience to understand the implications of each individual scenario.
• Efficiency can and must be optimised in all parts of
a drivetrain.
• Looking at each part in isolation, however, may not
ensure an optimal solution.
• Be sure that the overall system is fit for purpose.
Electricity+Control
July ‘14
22
