It might surprise you how quickly the face of industrial automation is changing. Technologies such as more advanced drives, FieldBus-based pneumatic installations and piezo-actuated valves all point to a rapidly evolving industry. This makes it interesting to note major trends happening in these areas.
A notable trend here is that drives can perform more complex tasks than in the past, but, in certain ways, the systems themselves are simpler and easier to use. Many companies that supply drives typically provide low-voltage (up to around 700 volts) AC and DC variable speed drives for speed control, usually for some sort of continuous process.
For example, certain variable speed drives provide higher levels of control for pump, fan and general-purpose applications, yet the devices themselves are easier to configure than was the case in the past. New wizards automate configuration and set-up by walking users step-by-step through the process. The wizards let users perform “cloning,” whereby they can set-up a drive and then use either the interface device or memory card to quickly put the same set-up configuration into another drive.
Moreover, features such as auto-tuning and motor-recognition options for servo drives that control position are also advancing. When users hook up a motor to a drive, it can now cause a small routine to run that “substitutes-in” parameters for 90 percent of the applications the drive will see.
Currently, many drives connect with all the major industrial FieldBus networks, but AC drives are increasingly moving toward Ethernet-based platforms. The Ethernet platform in general handles several different industrial field buses, including Ethernet, EtherCAT, Sercos, Ethernet Powerlink, Profibus and Profinet. Higher-end variable speed drives can also include specialist protocols such as BACnet for building automation and LonWorks for device networking.
What’s more, additional energy-saving technologies are becoming increasingly affordable. For example, AC variable frequency drives such as the AC890 can be provided with an active front end (AFE) supply. An AFE lets the common bus system be configured to feed what would otherwise be wasted energy — say when one of the motors on a machine is being mechanically pulled at a speed faster than its setpoint — back into the grid with sinusoidal currents and unity power factor. In the past, most engineers thought that regenerative drives were too expensive. But with rising energy costs, the systems are deemed cost-effective. Examples of efficient installations include equipment such as mine hoists and cranes for loading ships.
And things are changing with servo drives as well. Previously, the drives were controlled by analog signals through a centralized controller or an attached digital controller. The units still had digital-to-analog conversion. Modern drives are mostly all digital, meaning that feedback is digital, the control signals are digital and the drive might feature a digital signal processor as well. Users can thus configure drives as “dumb drives,” which take commands from a centralized control and provide digital hand-shaking information such as the drive’s position and speed. Current drives are easily configured to perform multiple tasks in one package, whereas older drives required lots of add-on hardware.
Changes are also ongoing in open-loop vector control systems. They are much improved over older “volts-to-hertz” or “volts-to-frequency-control” drives. Open-loop vector systems offer better accuracy and speed control as well as better torque characteristics than do volts-to-hertz systems without requiring a feedback device. Current AC drives can use sensorless vector control on permanent magnet servo motors as well as the more traditional squirrel-cage-style induction motors. The systems provide more torque and power in a smaller package for applications such as a new pump on a printing press. In addition, this technology is more dynamic because permanent magnet motors can stop and start more quickly than can motors that must generate two fields. This arrangement is a cost-effective and high-performance option for lower-power applications.
Also evolving are the methods for cooling drives. Typically, most drives are air cooled. But recent higher-power applications instead employ refrigerant cooling to take the heat away from the integrated gate bipolar transistors (IGBT). This method lets drives get more power out of a smaller footprint with reduced IGBT thermal cycling as an additional benefit. Parker has developed patented advanced two phase cooling systems which are integrated into high power drives which have very high power density.
Article supplied by Nic Copley, Vice President Technology and Innovation, Automation Group, Parker Hannifin Corporation.
Check out part two of this series to look at trends in FieldBus-based pneumatic and piezo-actuated valve technologies.
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