MAY-JUN 2018

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INTECH MAY/JUNE 2018 43 AUTOMATION BASICS From the simple air fan in the warehouse to the complexity of energy storage systems, water supply, or wastewater management systems—AC motors running at variable speeds play a key role. Because AC motors consume much of the electricity gener- ated worldwide, using AC drives to limit energy use can produce significant savings. Best practices for AC drive integration Best practices for AC drives include a thorough re- view of the application. A properly selected motor type, with the right-sized motor and drive, is the starting point for any application, and this requires a detailed review of the load characteristics. Also con- sider the nature of the energy supply to the drive and the environment in which the system will operate. In some instances, an AC transformer or supply reactor may be needed to provide a clean source of power. The need for dynamic braking units, by energy injection or by removal of energy with choppers, and braking resistors should be defined. Regen - erative energy-handling requirements should also be defined. Stopping a variable load, especially quickly and often, will stress the drive and motor and should be considered. An installation review, including protection re quired from other energy consumers on the AC drive supply side, is necessary in many cases, and proper grounding systems are also needed. Finally, there must be adequate room for the AC drive and its protective devices. For example, the enclosure type and size must be sufficient to provide cooling and protection from the environment (figure 2). Create a plan for programming the AC drive to provide the connected motor with the best opera- tional methodology and energy savings possible. Fortunately, many of the required capabilities are RESOURCES More in-depth information on this topic can be found in ISA books and training courses. Variable Speed Drives: Principles and Applica- tions for Energy Cost Savings, Third Edition Motors & Drives: A Practical Technology Guide Motors & Drives: A Practical Technology Guide – Instructional Supplement SP15 – Applying Motor Controls and Drives Training Class 22–25 October 2018, Newhall, Calif. 3–5 December 2018, Research Triangle Park, N.C. built into AC drives for this purpose. Some common capabilities include: l preprogrammed control for V/Hz applications l quick-start menus l safe torque off for the protection of operators and users l autotuning for motors when in sensorless vector mode l efficient handling of acceleration and deceleration ramps l current, frequency, and voltage limits l methods for handling excess system energy l options for controlling emergency stops All of these capabilities and more can be used to optimize operation of an AC drive/motor system and to ensure safe operation over the life of the system. n ABOUT THE AUTHOR Bryan Sisler (bsisler@ is the product manager for drives and motors at AutomationDirect. Sisler has been involved in the automation and the electrical/electronic field for 35 years and in the automation in - dustry for the past 27 years, mostly special- izing in drives, motors, and communications technologies at a vari- ety of large industrial manufacturers and dis- tributors. Figure 2. Unless specifically rated for field mounting, AC drives, such as these Auto - mationDirect GS2 drive units, should be installed in a con- trol cabinet to protect them from the environment, with proper spacing for cooling.

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