PLANT MANAGEMENT
equivalent VSD-control pump system. Te results highlight the advantages of VSD control at partial flow rates. Te curves with markers show the input powers required by an IE3-class induction motor operated at constant speed, and by the same motor with a VSD. Electricity (input power) usage is reduced by 80%, 61% and 35% at flow rates of 50%, 67% and 83%, respectively, compared to throttling valve control.
THE BENEFITS OF MODERN MOTORS Energy savings can be further increased by replacing induction motors with advanced synchronous motor technologies such as synchronous reluctance (SynRM) and ferrite-assisted synchronous reluctance (FA-SynRM). To compare the efficiencies of the different technologies, three motor drive systems were set up using an induction motor (as reference) and a SynRM and FA-SynRM motor. All three were rated 11kW with a nominal synchronous speed of 1,500rpm at 50Hz in IEC frame size 160. Compared to the reference induction
motor, which was a high performance IE3 efficiency class product, the SynRM and FA-SynRM motors provide additional annual energy cost savings of US$159 and US$281, respectively, for the constant torque duty profile. Te savings are US$122 and US$213, respectively, for the quadratic torque duty profile. Tese values correspond to payback times well below two years, which means these motors deliver significant cost savings over their life cycle. Compared to less efficient induction motor drive systems, the energy savings
could more than double. Synchronous motors not only improve energy efficiency, but they also typically operate at lower temperatures, which contributes to improved safety and higher reliability. Induction motors are relatively inexpensive and robust, and the lack of a commutator and brushes means they are reliable and fairly maintenance-free. Teir main drawback is their asynchronous speed, which causes losses in the rotor conductors. Tese losses reduce efficiency and increase heat production in the bearings, leading to shorter bearing lifetimes. Although VSD control is possible with induction motors, it introduces additional stator, rotor and VSD losses, resulting in even lower efficiency. In synchronous motors, the rotor moves at the same speed as the driving magnetic field, eliminating most causes of rotor losses. Te motor can therefore run at a lower temperature, which promotes longer lifetimes for components like the bearings and insulation system.
TCO FALLS Although the numbers will vary according to the application, energy makes up 50-95% of the toal cost ofownserhip (TCO) of a motor-driven pumping system over its lifetime. Big savings are possible but are often overlooked. For example, a customer recently told ABB that his plant had made progress on energy saving by eliminating 500W of light bulbs that had previously been continuously illuminated. Tis was indeed a saving but ABB’s experts told him how a 75kW motor-driven pump running continuously with a partly closed valve could
Upgrading motors and drives can improve safety and reliability
cut energy use by 50% and save 37,000W – 75 times what the light bulbs saved. Take a look around you and consider
this: you may be able to save millions of Euros a year in your chemical plants if you modernise your drives and motors.
DIGITAL INSIGHT Besides cutting energy costs, technical developments with drives now include functionality that greatly increases their value on centrifugal pumping systems. Process control can be made tighter due to continuous data gathering, which provides digital insight and enables predictive maintenance. For example, we can now sense what’s happening inside a pump, such as when it gets dirty or clogged, just from the drive data. Tis digital monitoring function tells the motor, and therefore the pump, to start ramping its speed up or down to clean the impeller before larger problems develop or even unexpected failure results. Other smart functions that modern drives can initiate and manage include procedures such as soft pipe filling, cavitation detection, sensor- less flow calculations, multi-pump control, level control, dry-run protection and pump cleaning. Predictive maintenance and remote condition monitoring enable the pumping process to be fine-tuned and also allows for deeper checkups on the health of any pumping system without having to physically examine the pump at its operating location. Tis is a tremendous advantage in the chemical processing industry, where there are hundreds of pumps spread throughout a plant, often in difficult to reach locations.
Petteri Hyytiäinen is with ABB.
www.abb.com
Chemical plants often have hundreds of pumps spread throughout the site
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