Ten years ago when DPA launched its Drives Supplement, the ac variable
speed drives industry was accelerating fast with a raft of new
technological developments. Paul Pryor now looks back over the past
decade and makes a few predictions for the next.
The past ten years has seen the ac drives industry behaving like the
fashion business, with new ranges being launched every few years by most
of the larger manufacturers. While some new introductions appear to be
little more than cosmetic reincarnations of what went before, the reality
is that new technology has prompted most of the changes.
Technological change has been on a less dramatic scale than that of the
early 1990s, when open loop flux vector control made its inroads into the
high performance end of the market. However, many of the advancements of
the past decade have been more to do with simplifying use, maximising
energy saving potential and improving manufacturing technology.
Software for drives has developed to allow greater intuitive programming.
While it was claimed a decade and more ago that modern inverters were
'plug-and-play', this was rarely, if ever, the case. Now it is fair to
say that some small drives, at least, are easy to install and commission
for basic tasks. Where the smoothness of the acceleration and
deceleration ramps is critical, such as in lift and hoist applications,
there is still the job of tuning to be done, but with 'autotune', this is
now easier to programme along with all the other parameter settings in
the drive.
The application of variable speed control to save energy in continuous
duty applications such as operating fans, pumps and compressors was
recognised a decade ago. Indeed, when the Climate Change Levy was
introduced in April 2001 the industry forecast a huge boom for the drives
industry. While this presumed bonanza never occurred, at least in the
industrial control market, there has been a steady increase in the
awareness of engineers and, hopefully, most of them now consider energy
consumption in new machine designs or installations.
The cost of manufacturing variable speed drives has come down
considerably, thanks to modern electronic design and automated production
methods. At the same time, the global consumption of variable speed
drives has risen sharply to enable much higher volume production. The net
effect of this has been to see prices tumble over a ten year period,
especially at the low-power end - the so-called 'commodity' drives -
where prices have reduced dramatically.
This fall in price has seen low-power drives prices achieve parity with
those of contactors. Price reduction clearly benefits the customer and no
doubt it has contributed to bigger sales volumes, but there is a trade
off. As low power drives become more of a commodity sell, larger
percentages of sales are being achieved through catalogue and
distribution partnerships and consequently the after-sales support
switches from the manufacturer to these suppliers.
Some drive vendors are also expert application engineers and the
expertise they offer users in support of their products is becoming a
differentiator between the various manufacturers. This shift in the
industry is being highlighted and addressed by trade bodies, such as
Gambica in the UK, to establish service level expectations in the industry
The next decade will see further technological changes; of that there is
no question. Where we see the obvious early further developments is the
implementation of open networking. Moves towards an expanded adoption of
embedded industry standards such as Ethernet are gathering pace. The
opportunities for communication using TCP/IP and interfacing via standard
web browsers make the design, development and implementation of
automation systems simpler and more open.
We predict that over the next decade there will be further tec