Modern drives enable existing motors to run faster

When Exopack Advanced Coatings, a manufacturer of coated papers, films and speciality substrates, urgently needed to install two replacement variable-speed drives, it chose products from the Parker SSD Drives AC890PX range. Not only did the new drives prove easy to install and straightforward to commission, but they also provided an improvement in performance that saved the company from having to install larger and more costly motors to increase the capacity of its plant.

As part of its ongoing commitment to protecting the environment, Exopack Advanced Coatings operates a large and effective pollution abatement plant at its UK manufacturing site in Wrexham. Central to the operation of the plant, which deals with the exhausts from the site's production machinery, are two fans, each of which is driven by a 180kW induction motor. The speed of the fans is continuously regulated so that there is zero pressure differential between the abatement plant intake and the machine exhausts.

The abatement plant has now been in operation for a number of years and, because of Exopack Advanced Coating's success and the resulting growth in its business, it had recently become apparent that an increase in capacity was needed. When the site was in full production, it was difficult for the fans to maintain the necessary zero pressure differential, even if they were operating at the maximum attainable speed.

Urgent replacement

To address this issue, Exopack Advanced Coatings planned to install larger fan motors. However, before this could be done, difficulties were experienced with the existing variable-speed drives that were becoming increasingly unreliable and, because they were obsolete, harder to maintain. To guard against complete failure, which would have seriously impacted the manufacturing operations on the site, the decision was taken to replace the drives immediately.

Dan Hitchcock, Project Engineer, states: "We chose drives from Parker SSD Drives for this critical application, partly because they are well specified and offer excellent value for money, and partly because of our positive experiences with the company's products in other applications. We have always found that Parker drives just work, and that they are completely bombproof - it would be hard to ask for anything more!"

The latest AC890PX modular drives were selected by Exopack Advanced Coatings. Available with ratings of up to 400kW, these compact units are just 500mm wide, enabling them to be installed easily into the limited space available. They use sealed plug-in modules for all major functions, which makes them easy to service, and incorporate a wide range of features as standard, including line fuses, line reactors and a disconnect switch. In addition, they support V/f, sensorless flux vector and full flux vector modes of operation.

Hitchcock continues: "Because everything we needed for our application was built into the drives themselves, installation was fast and straightforward. Setting the drives up using the free software provided by Parker SSD Drives was just as easy. Within three days of them being delivered to site, we had the drives installed, configured and fully operational."

Drive optimisation

Initially, the drives were set up for V/f operation, as were their predecessors. Even under these conditions, Exopack Advanced Coatings noted that the motors were able to run close to their original maximum design speed, which had not been possible with the previous drives. The engineers at the company then decided to see if further improvements could be achieved by switching to sensorless flux vector operation.

The results greatly exceeded their expectations. Because the fans could now be operated under full control at higher speeds, the capacity of the abatement plant was increased by 5 per cent without the need for other modifications of any kind. This was sufficient to cater for current demands of the production equipment, with some reserve in hand. As a result, the engineers decided that it would no longer be necessary to install larger motors, thereby saving the company in excess of 10,000.

Nor is this the only saving that Exopack Advanced Coatings has made as a result of installing the new drives; it is also saving money because of their greater energy efficiency. Hitchcock says: "Like all conscientious companies, we monitor our energy usage very carefully, but we did not really need any instruments to tell us that the new drives were much more efficient. When the old drives were in operation, the temperature of the switchroom in which they were installed was always around the 30degC mark, which made it a good place to be when the weather was cold.

"With the new drives, the temperature in the room is just a degree or two above ambient. That has somewhat reduced its attraction on cold days, but it does instantly confirm that we are now wasting far less energy that we used to. Another indicator of their efficiency is that the new drives are much quieter in operation than their predecessors. Low noise levels are not a particular requirement in our application, but they are undoubtedly the sign of an efficient, well-built drive."

Many users of older variable-speed drives believe that there is little reason to update their existing installations. As Exopack Advanced Coatings' experience with Parker SSD drives has shown, however, modern drives can not only improve reliability, they can also deliver valuable energy savings and even, in some cases, enhance the capacity of existing plants.