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 technology advances, yet still easier communications, greater intelligence within even standard variable speed drives and an expansion of their application as older plant with direct online and star-delta type starting arrangements are replaced.
Paul Pryor is with Schneider Electric