Taking a drive to ENERGY SAVINGS

`After one year of using the drives, the savings exceeded our expectations and gave us a payback time of just 16 months,' says Tony Wallace, utilities development manager at Glaxo-Wellcome's Ulverston site in Cumbria. The drives in question deliver what amounts to an annual saving of over £30 000 and were supplied by ABB Industrial Systems.

In a typical example of how variable speed drives (VSDs) can cut energy costs, the drives - installed by Slater Drive Systems, the local ABB drives system house - control the speed of supply and extract fans on one of the Ulverston site's boiler systems. Previously, the 200 and 150kW fan motors ran at full speed with flow controlled by dampers. But, as the 80 tonne/h boiler was at low load for long periods, Wallace was convinced that VSDs could considerably reduce his electricity consumption. So successfully, in fact, that four more have now been installed on cooling tower fans with expected savings of £15 000 a year from each.

SAVINGS DONE AND DUSTED

Another example comes from Mitsubishi's files. The company's PLCs control a process at a Melton Mowbray factory that produces cat litter from Fullers earth. But during a routine site visit by a Mitsubishi engineer, the site manager indicated that they wanted to upgrade the plant's dust extraction system. On further investigation, it was found that the motors on the extraction system were always run at full speed, not only wasting energy but helping to generate tanker loads of dust for disposal each month.

Mitsubishi's answer was to engineer a system that not only recycled the dust but also saved energy by using a motor with a VSD. The project paid for itself in less than a year and has saved money ever since.

That particular project was engineered, installed, commissioned and continues to be maintained by one of Mitsubishi's `Drive Systems Centres'. These have been set up at strategic sites around the country (Peterborough, Leicester, Preston, Peacehaven and Bromsgrove) to service the increasing demand from end users for a `complete package' or systems approach to machine drives. The centres claim close connections with the industries they serve and all offer strengths in areas such as water, paper, packaging, plastics and food and drink processing.

To meet the requirements of those industries even further, Mitsubishi has now introduced inverters rated at up to 450kW, some five times the power of the company's previous maximum. Drives of this size power pumps, fans, extruders, blowers and other large processing equipment. There are seven sizes available in the new Meltrac range of variable frequency drives, capable of controlling 3-phase ac motors of up to 75, 110, 150, 220, 280, 375 and 450kW. Designed to simplify system integration, they feature RS422/485 interfaces and fibre-optic links.

Next month ABB will be unveiling some additions to its drives range at the Drives and Controls 1997 exhibition in Telford (from 11-13 March). The company's ACS 607 range of DTC (direct torque control) drives will be on show in their latest high power configuration of 630kW, double that of the previous top-of-the-range models. For industries such as water with their powerful pumping requirements, the ACS 607 drive now provides a broad range from 2.2 to 630kW. And for even larger system requirements - up to 2MW in, for example, certain offshore or petrochemical applications - the new DTC-based system drive features a common dc link that feeds a series of drive modules, which in turn power the various motors connected to the system.

HID has also chosen Drives and Controls '97 as the venue for the launch of the Hitachi JE300 drives. These have power ranges from 132 to 500kW (or 650kW for fan and pump ratings). Like its J300 smaller sister, the JE300 uses sensorless flux vector technology to provide what is claimed to be exceptionally smooth running and very high torque. It is aimed at the water and utilities industries and comes in both 6 and 12 pulse versions. The significance of this, at least to electrical engineers, is that the 12-pulse inverter is said to radically reduce harmonics onto the electrical supply.

Announced last month was Danfoss' move from what the company considers to be its market leading position in the small and medium-sized drives market to it being a global supplier of all sizes of drive. Marking this switch in emphasis was the introduction of the VLT5000 drive, an expansion of the current VLT3000 range so the company will be able to offer sizes from 0.75 to 355kW.

Danfoss says it has paid particular attention to the ease of programming. With a no-spin `automatic motor adaption' feature (AMA), every VLT5000 automatically adapts to any motor without the need to de-couple the drive from the load and spin the motor - a potentially dangerous, set-up procedure.

As next month's Drives and Controls '97 will clearly show, the drives manufacturers are leading the way to more energy-efficient electrical equipment. Process engineers, take note.

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