Drive brings speedy rescue

QUICK thinking and advanced technology recently allowed Rotoruas Ideal Electrical team to help a local timber processing plant limit down time and lost production when one of its large moulding machines broke down.

Rotoruas Hume Pine processes high quality pine mouldings, predominantly for the export market. Much of the companys production is processed by a Wadkin moulding machine that runs seven electrical motors at 100 Hz (around 112kW in total).

All these motors were supplied from a mechanical frequency converter.

When the frequency controller coughed and died early one Wednesday morning, the moulder ground to a halt and the company contacted Ideal Electrical.

Branch manager Robin Thompson says Ideal Electrical has an extensive track record in industrial/commercial applications, and his team immediately recognized that the frequency controller breakdown presented Hume Pine a unique opportunity. Not only to upgrade the moulder, but also to get it operational very quickly and thereby limit down time.

To repair the frequency convertor would have cost an estimated $10,000, but more significantly, it would have taken about ten to 14 days to do the job, says Thompson. Furthermore, the frequency controller had always offered limited flexibility with controlling the moulder, and we knew replacing it with a variable speed drive offered a far superior solution.

He contacted Russell Moorhouse, the Schneider Electric customer services representative based in Tauranga. Moorhouse immediately drove across to the Hume Pine site in Rotorua to evaluate the situation.

By three oclock that afternoon, after discussions with the Hume Pine site engineer and his electrician Peter Fraser of Peter Fraser Electrical, Ideal Electrical and Schneider Electric had developed a proposal: replace the frequency controller with a Telemechanique ATV 71 variable speed drive.

Hume Pine accepted the concept.

The VSD initially appeared to be a more expensive option, says Thompson. But its benefits far outweighed the additional cost, especially because it allowed the company to have the planer up and running in days, rather than weeks  representing a significant saving in lost production.

The VSD also offered a variety of additional benefits. For a start, it presented a substantial saving in space. The old frequency converter was quite a large beast, driven by a 50 horsepower motor, says Thompson. The ATV mounted in its place used a fraction of the space.

Faster ramp up and ramp down sequences, with far more control than the frequency converter could ever provide, has created slicker production throughput, adds Thompson. Where the machine had previously taken around three minutes to stop after switch off, it now stops within 10 seconds. That presents enormous advantages for swapping planer knives and set-up changes.

Furthermore, the moulders motors run at around 6000rpm, and the VSD makes it very easy to vary moulder head speeds to maintain quality in different applications. Combined with the smoother and quicker ramping up and ramping down, that translates into a more efficient machine, and ultimately, to a saving in operational costs.

Perhaps most significantly, says Thompson, Hume Pine now has a much more modern platform on which to plan future production and expansion.


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