Smart Controllers Designed To Treat Motors Softly
The company says that by providing integrated features and previously unavailable advanced functionality in a compact, 45-mm housing, the controllers can offer users flexible, cost-efficient solutions for a wide range of motor control applications.
Typical applications for the controllers include compressors, fans, chillers, lifts, pumps, and crushers.
SMC BENEFITSThe big benefit to these new products is their ability to soft start a motor, as opposed to traditional electromechanical starting or even drive starting, says Steve Litzau, product manager for the SMC product line, Rockwell Automation, Milwaukee, WI.
Using soft-start technology can reduce or minimize customers’ downtime, as well as their operating costs. That’s because the SMCs minimize the high in-rush currents that are normally seen with other starting methods, as well as minimizing the high starting torque seen from the motor.
“What that will do for customers down the road is minimize the amount of maintenance they’re going to have on their system or their process. We’re going to reduce the mechanical stresses as well as the electrical stresses on their system, which will minimize their overall maintenance on the system,” says Litzau.
Rockwell Automation has an existing line of controllers. However, Litzau calls the SMC controllers an extension to the existing product line, because they have been dramatically improved.
In the existing product line, the controllers have silicon-controlled rectifier (SCR) controls. When the motor gets up to full speed, those SCRs gate fully on; the SCRs are still controlling the motor, and they’re still producing heat inside the unit. The new products have a SCR bypass contactor built inside each unit, which takes the SCRs off-line. The SCRs no longer generate the heat they normally would during run time.
“What that allows us to do is get this product into a much smaller package,” says Litzau. “If the product needs to be put into an enclosure, the enclosure now can be greatly reduced because the heat generation is greatly reduced.”
A built-in overload is another feature that is not available on the existing line. “We’re essentially consolidating as many components that would normally be required in a system and putting them all into one device. The customer only has one product to purchase,” Litzau says; “in the past it might be two or three different catalog numbers that they would have to purchase and assemble.”
WHEN THEY SHOULD BE USEDVariable-frequency drives (vfd’s) are often used to save energy; Litzau notes that the SMC may be a better fit in certain types of applications, such as compressors, chillers, conveyors, bottling operations, and people movers.
“What a vfd allows you to do is control the speed throughout the entire process; however, in applications like hvac, where customers want to get their motors up to full speed and let them run at full speed, an SMC becomes a much nicer option for them.”
That’s because the SMC controls the start-and-stop profiles of how the motor is operating. The SMC ramps the motor up to full speed, then lets it run at full speed before ramping back down. A vfd is usually applied in places where there’s a need to control the speed of a process all the way through the time in which the motor is running.
It all comes down to the application: In some, vfd will do a better job than an SMC; in others, an SMC will do a better job than a drive.
SMCs also can be retrofitted into existing applications and onto existing motors. “There are numerous applications where an SMC can be applied,” says Litzau. “An SMC will reduce the stress and strain on any motor. We’ve been applying SMCs to applications that have been running for over 15 years, plus we have SMCs out there that are over 15 years old, and they’re still doing a great job.”
Sizing is no problem, he says. All that’s necessary to do is obtain the full load amp (FLA) setting on the motor, then size the SMC appropriately to the FLA of the motor. That’s it. Litzau notes that retrofitting is a breeze because SMCs are so small.
Even though the new SMCs are smaller than their predecessors, Litzau says SMCs will probably become even smaller in the future. “Our customers ask for them to be smaller, have more features, and to also be less costly.”
Such are the requests made of all equipment manufacturers in the hvac industry: smaller, better, and less expensive.
Sidebar: The Nitty Gritty On ControllersThe SMC-3 controlling device includes standard electronic overload protection with adjustable trip class, advanced motor and system diagnostics, configurable auxiliary contacts, and multiple start and stop modes. It is designed for maximum control of standard squirrel-cage induction motors.
Overload protection options include a choice of trip classes (10, 15, 20, or off) and selectable overload reset (manual or automatic). Fault diagnostics cover over temperature, phase loss/load loss, phase-reversal conditions, phase imbalance and shorted silicon-controlled rectifiers (SCRs). DIP switches allow easy, precise, and secure setting of the start-stop profile, overload trip class, and auxiliary contact characteristics, the company says.
The SMC-Delta is a reduced-voltage starter for star-delta (six-lead motor) applications, incorporating a transitionless start and requiring less panel space than a traditional electromechanical starter. The starter combines contactors, overload relays, timers, and internal power and control wiring into a single product with a compact footprint, making installation quick and easy, says the manufacturer.
The SMC-Delta includes six motor winding terminations, eliminating the need for major wiring changes to upgrade existing applications. It also offers simplified wiring and easy setup and maintenance for star-delta motors. The SMC-Delta allows one device to be configured for many applications.
For more information about either product, contact the Rockwell Automation Response Center, 10701 Hampshire Ave. S., Bloomington, MN, 55438; 800-223-5354, ext. 1466.
Sidebar: Motor Planning Kit, Calculator AvailableST. LOUIS, MO — Emerson Motor Technologies said it is taking a proactive role in helping companies cut their energy costs through its sponsorship of the “Motor Decisions Matter” campaign. The national campaign encourages sound motor management and the use of the National Electrical Manufacturers Association (NEMA) Premium™ motors.
Emerson Motor Technologies joins 28 other motor manufacturers, trade organizations, government agencies, and energy conservation groups in sponsoring the campaign.
As a sponsor, Emerson promotes and provides tools designed to enable commercial and industrial customers to develop a motor plan, with the assistance of their local distributor, repair center, or utility representative. A motor plan addresses common motor decisions before equipment failure. Emerson said this ensures motor availability, reduces downtime, and lowers energy costs.
The sponsors have made available a free MotorSlide Calculator™ and Motor Planning Kit to help put together a motor plan. The calculator computes a motor’s annual energy costs, the annual energy savings of using a premium-efficiency motor, and a motor’s efficiency. The Motor Planning Kit, which can be downloaded off the Motor Decisions Matter website (www.motorsmatter.org), contains information, statistics, links, case histories, examples, and tools designed to assist companies in developing motor management plans designed to save on energy costs.
To obtain an information packet containing the calculator and planning kit, contact the Department of Energy’s (DOE’s) Office of Industrial Technologies Clearinghouse at 800-862-2086.
The campaign targets three key audiences: executive-level managers; maintenance repair and operation employees, plant managers, and engineers in industrial markets; and distributors and repair firms.
Helping customers identify appropriate applications for premium motors is an important component of the campaign, said Emerson.
NEMA recently released a premium efficiency specification and brand — called NEMA Premium — that motor manufacturers, distributors, and utilities can now embrace in common. A product must meet all of the NEMA-specified criteria in order to be qualified as a NEMA Premium Compliant Electric Motor by its manufacturer.
Publication date: 03/18/2002