Line builder standardises on Control Techniques AC drives

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Phoenix Dryers has standardised on Unidrive SP and Commander SK variable-speed drives from Control Techniques for its drying and coating lines because of the drives' ease of installation and programming, reliability, versatility, availability, and the support it receives from Control Techniques.

Phoenix Dryers has standardised on using variable-speed drives from Control Techniques for its drying and coating lines. Managing Director John Beardsworth states: "We always fit drives from Control Techniques unless the client specifies otherwise. We find them easier to install and program, and they are exceptionally reliable."

A typical line is one for rubber-coating a cotton web as the first process in the production of industrial textiles. This employs a total of 14 Unidrive SP and Commander SK AC drives from Control Techniques. Beardsworth says: "With a challenging build target, we found ourselves having to do the first-time turn on the entire line in front of a delegation from the customer. They were more than a little impressed that it ran up perfectly in synchronism with spot-on tension control. Even when an encoder failed, we reverted to open-loop drive control on that particular section and it still performed faultlessly."

The coating line comprises an unwind section with an air brake controlling tension, followed by a 100-foot accumulator section, a spray/dipping coating unit, a dryer/curer and a take-off roll with dancer to control tension. Unidrive SP AC drives are used throughout, with additional Commander SK AC drives providing control for the exhaust and recirculating fans. The master for the line is a water-cooled pull roll drive, positioned just before the take-off section, and this provides a reference master signal via DeviceNet to all the drives and the controlling PLC to keep the line synchronised.

Drive applications

The first of the Unidrive SP drives on the line is a 0.75kW unit controlling the eight-inch diameter nip roll feeding the accumulator with the 60-inch wide fabric web. An identical drive controls the S-wrap pull rolls, followed by a 1.1kW reverse dancer backup roll for tension control. The web then either goes through applicator rolls, for direct coating, again with a 1.1kW drive, or is diverted through a dipping process, both followed by a nine-inch diameter squeeze roll controlled by a 1.1kW drive. Also on this section, a 0.75kW Unidrive SP controls a seven-inch diameter metering roll.

Throughout this process and the subsequent drying/curing, web tension is critical. The tolerance band is adjustable up to 300lb (136kg) and controllable to better than +/-0.5 per cent, which is crucial to eliminate tension lines in the web, as well as to prevent web breaks. Beardsworth comments: "We have found problems with maintaining tension with some other drives, but drives supplied by Control Techniques always give accurate tension control."

The drying/curing section has a graduated temperature from 62 to 140degC and the web exits the tunnel into a web-guider, where load cells monitor the tension and provide a feedback signal to the reversing drive. The hot web is taken through a water bath by water cooler pull rolls controlled by a 0.75kW drive. The rewind section has two 1.5kW drives, fitted with SM-Applications Lite modules supplied complete with Control Techniques' rewind software, for the two 36-inch, 0.2-3.2rpm rewind rolls.

All of the Unidrive SP drives have encoder feedback and SM-DeviceNet communication modules, as well as an LED keypad. Additionally, all of the drives are heavy-duty rated to give 150 per cent overload.

Fan control

The four 7.5kW recirculating fans and the 11kW exhaust fans are all controlled by Commander SK heavy-duty AC drives and all have flameproof motors. Beardsworth explains: "This plant can use either water-based or solvent-based coating materials. In the case of the latter, the safety and economy of the plant is totally dependent on the accurate and reliable operation of the fan system." Sensors monitor the levels of solvent in the exhaust and feedback to the drives. Levels in the recirculating air are kept well below the lower explosive limit (LEL) by controlling the amount of flow to the exhaust. The exhaust air is then fed to an abatement plant to prevent release of solvents into the atmosphere. Beardsworth adds: "It is important to recirculate as much of the hot air as possible to keep energy costs down, but even more important to maintain a good safety margin."

The Unidrive SP 'Solutions Platform' AC variable-speed drive range spans 0.37kW to 1.9MW. It is configurable into five operating modes: open-loop, RFC (rotor flux control), closed-loop vector, servo, and regenerating modes. With a range of plug-in option modules, its onboard PLC can be supplemented with programmable, specialist feedback and communication modules.

Commander SK drives are small, yet powerful, taking up very little panel space, and are said to be renowned for their reliability. They are easy to fit, set up and use with all the ten parameters most users need being accessible from the display keypad that is included as standard. Very important in today's carbon-aware economy is its energy-saving efficiency and state-of-the-art manufacturing standards that are responsible for the drive's outstanding reliability.

Beardsworth concludes: "Drives from Control Techniques are our drives of choice for so many reasons. Feedback from customers confirms that they are very, very reliable – but if there is a problem, it is reassuring to know that the worldwide network of Drive Centres with stockholding will provide rapid support and replacement if needed. We appreciate the excellent support we get from Control Techniques here in the UK and we like the flexibility of the drives in all circumstances – connectivity to all major networks and feedback devices and straightforward programming, for instance. Their aim of supplying quality products and a quality service meshes well with our own philosophy."

Follow the links for more information about Unidrive SP and Commander SK AC drives.

12 June 2012

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