Operation & Maintenance of Power Plants
II. Embedded applications functions, such as PID control, droop control, and function block programming provide system level control without the use of a stand-alone controller.
A unified solution Modern manufacturing regimes need higher efficiency, more flexibility and greater reliability - all necessary to reduce manufacturing costs. To meet those needs, Danfoss VLT Drives has developed the VLT FlexConcept. Tis new drive system uses modern motor technology combined with the advanced inverter drives and in a unified solution. Te company says it combines the world’s most efficient variable frequency drives VLT AutomationDrive FC 302 and VLT Decentral Drive FCD 302 with the highly reliable and hygienic VLT OneGear Drive and compact and efficient permanent magnet (PM) motors. Tis results in: higher efficiency; fewer variants; lower training and maintenance costs; flexibility; and higher reliability. Overall, says the company, this equates to a reduction in production and manufacturing costs. Danfoss offers the choice between VLT drives for centralised location in a control room, cabinets or wall-mounted and VLT decentral drives for mounting close or even onto the drive motor. Tis gives users the maximum flexibility in plant design and maintenance. Both the geared motor unit VLT OneGearDrive
and the VLT Decentral Drive FCD 302 meet the toughest washdown and hygiene-specific conditions - making them the ideal combination for food and beverage plants. Te VLT FlexConcept reduces the number of
drive variants in a plant by up to 70 per cent, which also ensures maximum flexibility and the need for the minimum number of spares. Danfoss says that the high level of energy efficiency
(up to 90 per cent withVLT OneGearDrive combined with VLT AutomationDrive FC 302) reduces total cost of ownership by up to 25 per cent compared with conventional systems
Control is key, too According to Siemens, while electric motors represent over 65 per cent of the total industrial power demand, approximately 70 per cent of the installed motors today do not use optimal motor control – which is bad news for a greener world. Te good news is that almost every company has the potential to tap into enormous energy savings by using Siemens variable frequency drives (VFDs) for motor control on pumps, fans, and compressors. Te energy savings potential is substantial – in some cases up to 70 per cent. But that’s just the beginning of the game. Energy-efficient VFD systems can assist in a number of other ways such as reducing production costs, improving product quality, and ultimately lowering carbon dioxide emissions. Such improvements are boosted by the company’s
SinaSave software which calculates how great the savings potentials are for a user’s specific drive applications: savings of up to 70 per cent. Siemens offers this innovative and user-friendly software to calculate the energy efficiency and it can be downloaded at no charge. SinaSave also functions as an energy savings calculator, showing how quickly an investment in an energy-efficient motor for line supply operation or a frequency converter for variable-speed operation will pay off. Frequently, the payback period is just a few months, says the company. For line operation, SinaSave’s energy savings calculator determines the cost saving and payback period for our energy-saving motors in the high efficiency classes IE2 and NEMA Premium compared with motors of standard efficiency class IE1 or EPACT, individually selected, or common motors – as part of a complete system analysis. ●
Digital drives overcome burnout problem at steel plant T
he replacement of analogue DC drives with digital DC drives from Control Techniques for the
energising of electro-magnets at Evraz Highveld Steel and Vanadium Limited in Mpumalanga, South Africa, has reduced downtime and increased throughput on a steel bar production line. The electro-magnets are used on
overhead cranes at numerous points in the production process for the transport of steel bars. Previously, analogue DC drives
were proving unreliable and destroyed numerous electro-magnets as a result
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of being over-excited, causing excessive current flow. It was decided that a changeover to more closely controlled digital DC drives was the answer and Mentor MP DC drives from Control Techniques were chosen for the task. The Control Techniques solution
comprises a 210 amp/480 volt, four- quadrant Mentor MP DC drive for each electro-magnet, in conjunction with a freewheel diode that dissipates the back- emf into the magnet when the magnet is de-energised, providing a discharge path for the current. Evraz Highveld specified the need
to regulate the current very accurately to prevent over-current damaging the magnets and the drives are configured in torque control. The arrangement implemented ensures
that the intensity of the magnetic field is maintained irrespective of ambient temperature. As a result of the replacement of the analogue DC drives with Mentor MP units, damage from burning of the windings through excessive current has been completely eliminated, reducing maintenance and downtime while improving average line throughput. ●
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