Page 5 - Industrial Technology EXTRA 28th September 2020

certainly the benefits of the VSD and the steadily
increasing sophistication of the product as
technology has marched on has seen growth rates
little short of phenomenal.
This success comes from far more than just
being able to turn a low-cost electric motor at a
specified speed or torque. Increasingly, it comes
from the ability of the VSD to address evolving
trends or to tackle industry issues – from the
requirement for greater energy efficiency to the need
for increased safety. Today, all of this and more is
taken for granted on even the most standard VSD, need for a separate external controller. There is also
while the more sophisticated products extend the the ability to alter the ratio between the master and
flexibility of VSDs by operating with an increasingly the slave, providing an electronic gearbox and all of
diverse range of motor types. this is possible simply with the addition of an
As an example, the latest VSDs from Mitsubishi encoder option card and the setting of a few
Electric can control not only standard induction and parameters.
higher efficiency motors but also multi-pole surface
permanent magnet (SPM) and interior permanent Smart functions in drives
magnet (IPM) motors. Later this year there will also While the likes of position control and master-slave
be the capability to drive a synchronous reluctance synchronisation represent useful additional
motor, offering ultimate control from a single drive. functionality, it is the latest smart functions that
However there is more, with advanced really open up the potential of the variable speed
functionality extending the capability of the modern drive as an automation platform. For example, it is
variable speed drive beyond just speed and torque now common to find a PLC embedded within the
control. With the addition of an encoder on the VSD, enabling many small and even medium sized
motor, the VSD can also offer position control, automation applications to be solved by combining
delivering near servo performance in applications logic control and sequencing with the drive’s ability
that wouldn’t warrant the cost of the servo motor or to control the motor.
where the power requirement is too high. Hoists In multi-drive applications, as long as one of the
and conveyors would be typical applications. VSDs has an in-built PLC, it is possible to use a VSD
Another interesting feature is master-slave link function to facilitate communication between
synchronisation, where the drive can eliminate the multiple drives, allowing a small-scale master-slave
need for mechanical components such as shafts, control system to be implemented without the need
cams and gears. If two shafts need to be for an additional PLC. Typical applications might
synchronised, the VSD can be electronically locked include a self-contained, duty assist, standby
to an encoder on the first shaft and use this signal pumping system (taking advantage of the pump
to drive the motor on the second. As the master control capabilities of the modern VSD) or a multi-
reference changes, the slave has to follow. This VSD conveyor system. With the addition of an
flexible control philosophy has been used in operator interface such as a Mitsubishi Electric GOT
countless conveyor applications, eliminating the HMI, the solution is a completely self-contained

September 2020 • INDUSTRIAL TECHNOLOGY EXTRA • p5