Traditionally, the primary use of drives has been in applications such as powering pumps, fans and conveyors. While they will continue to be used in these applications, today's end-users have a different approach from that of a decade ago.
Drives are now fully developed and more widely accepted as a product. The need to answer the question, "what does it do?" has been replaced by the expectation that the drive will "just do it." This attitude shift includes the assumption that drives are simple to buy, install, start-up, commission and own and run.
Drives are also finding new applications: in exercise machines, pizza ovens, honey centrifuges and car washes. In these applications, the drive is definitely considered a commodity, and OEMs who may not have traditionally used drives, are once again demanding pure simplicity. In fact, a recent survey showed that simple controls and set-ups (70 percent) and convenient operator interfaces (53 percent) were rated as "very important" by AC drives users.
The Quest for Miniaturization
Drives can now be used in domestic washing machines, which is a testimony to their extreme compactness. Drives have become smaller, more capable, easier to use and cheaper.
Smaller drives are easier to install. Panel builders can fit more drives into a standard cubicle, so the whole panel can be smaller and a smaller, less costly control rooms can be used. OEMs can also fit drives into their equipment, even in cranes-an application that has always had very limited space for the drive.
Drive size reduction comes from the use of fewer components, greater packing density, improvements in semiconductor technology and improved cooling techniques. In fact, there has been a ten-fold decrease in the size of drives over the past 10 years.
Lower Costs
Reducing the number of components in a drive cuts costs. We predict that, over the next few years, the parts count of our drives will be reduced by approximately 20 percent through the use of integrated electronics to eliminate separate components, including external flash, RAM memories and analog/digital converters. Mechanical parts are also being integrated by combining frames and enclosures to perform multiple functions.
Reducing part count also enhances reliability: fewer parts mean fewer interfaces and mechanical fixings, which are often a source of failures.
Improved Cooling
Power semiconductors have also helped to improve drives. A reduction in the power losses per-unit-area-of-silicon used means that the same silicon area is able to handle more power. These smaller semiconductors have reduced the need for cooling within the drive, allowed the use of smaller heat sinks, reduced air volumes inside the drive and decreased the size of the drive. The only limitations are the terminals because they must accommodate cables large enough to carry sufficient current to the drive.
The development of power semiconductors and cooling technology have enabled miniaturization of drives.
Considerable research and development effort is devoted to developing new cooling techniques, as well as reducing the need for cooling.
While air cooling is likely to remain the dominant technique, liquid cooling is finding increasing use in wind power, transportation and marine applications.
Increased Functionality
These ever-shrinking drives contain ever-expanding functionality from new software. Today's software monitors, diagnoses, configures and archives information and parameters concerning drives in industrial plants.
Setups are performed entirely using software functions, and then downloaded to the appropriate drives.
The set-up information is archived for future retrieval. To obtain the full benefit of this technology, however, operators must continue to refer to the user manual. Intelligent control panels are in the works that will significantly decrease the need for paper-based manuals. The secret, though, is to find an easy way of accessing this functionality. Enter the keypad.
The True Value of the Keypad
Most equipment investment decisions now carry a proviso for fast installation to ensure that production will start rapidly and smoothly. The speed with which a machine can be up and running after the installation of new equipment or after a maintenance shutdown is paramount. If a machine breaks down, it can cost the operator $20,000 per hour, so easy set-up and commissioning are a priority. Such urgency increases the risk of errors in installation and commissioning. These can be overcome by eliminating manual intervention wherever possible; the keypad is central to this aim.
The Magic of Wizards
"Wizard" software on new drives can guide the user through various procedures. A start-up assistant can guide the user through both start-up and commissioning by asking questions in plain text language. There are no complex parameter numbers or codes. The product's intelligence helps the user through the commissioning process.
For an OEM who might buy 4,000 AC drives per year, the time saved by using an easy start-up system can be significant. It can cut 15 minutes from the commissioning time of each drive, equating to a time saving of 1,000 hours per year. For an engineer working 2,000 hours per year, this is half a man-year.
Specialist HMI
Another tool that makes life easier for the OEM is a hand-held human-machine interface (HMI) that allows drive parameters to be installed in seconds. The device can be used to select and set parameters, and to copy configurations between drives, without even powering up the drive.
Application-Specific Solutions
AC drive users can further reduce costs by employing application-specific drive solutions. These drives incorporate incremental functionality that supports specific applications such as fan and pump control, mixers or crane controls. They can reduce the total cost of ownership through shorter start-up times, lower integration costs and improved machine productivity.
Time savings during commissioning can range from one to several hours. The process does not require expert programmers, so it saves the considerable expense of sending commissioning engineers around the globe to fine-tune individual drives.
An Intelligent Pump Control (IPC) software module eliminates the need for an external PLC (programmable logic controller) and can help to save energy, reduce downtime and prevent pump jamming and pipeline blocking.
The IPC contains all the common functions needed by water and waste utilities, industrial plants and other pump users through six pump control functions.
Adaptive programming in the software consists of a set of simple to use blocks that can be programmed to perform any operation from a predefined set of functions. All common mathematical and logical functions as well as switches, comparators, filters and timers are available. Today, users can have the power of a small PLC inside their drive.
A further breakthrough is that programming can be implemented using the standard control panel. No special hardware or software programming tools are needed. As a result, the programming takes only a few minutes and can be performed onsite, during commissioning.
Three Modules
Despite their significance, these advances are only half the story. New machinery drives feature the use of three plug-in modules that house the heart and brains of the drive. On the hardware side, there is a power module and a control interface module, while the software module provides easy programming of the relay logic or PLC routines an OEM may require for its own applications. These modules can reduce commissioning times, eliminate the need for external maintenance engineers and minimize unpredicted production line stoppages.
By providing separate units, both the power module and control interface can be shipped to site and installed ahead of the software memory unit. When the installation is complete, the memory unit, which can be programmed on the OEM's own premises with specific application code, can be delivered and simply plugged into the control interface on site.
The modular approach also allows the number of product components and variants to be reduced.
Since there is no need for on-site programming or the connection of any communication cables to PCs, time savings during commissioning can range from one to several hours. The process does not require expert programmers and saves the considerable expense of sending commissioning engineers around the globe to fine tune individual drives.
The Future
AC drives will be smaller, more intelligent, easier to install and control, have better communications and be suitable for many more applications-particularly at the low power end of the range-all at a constantly reducing price. What better future could drive users ask for?
Pumps & Systems, June 2008