Product category:
Industrial Drives/Controls
News Release from: Schneider Electric | Subject: Variable speed drives
Edited by the Engineeringtalk Editorial
Team on 26 April 2000
Altivar drives go to the movies!
Bristol cinemagoers are now enjoying improved screenings of classic and archive movies, thanks to an Altivar 18 variable speed drive from Telemecanique.
Bristol cinemagoers are now enjoying improved screenings of classic and archive movies, thanks to an Altivar 18 variable speed drive from Telemecanique, a brand of Schneider Electric The drive has been installed on one of the 35mm movie projectors at Bristol's Watershed, a British Film Institute Regional Film Theatre, and allows the projector to run at precisely the right speed for the film which is being projected
"Modern sound films all run at a speed of either 24 or 25 frames per second (fps)," said Watershed technician, Ray Luton, "but the silent archive films which we often project run at slower speeds, usually in the range from 16 to 20 fps.
It's import to get the projection speed right, or the result is unrealistic, speeded-up motion, which can completely kill the atmosphere and impact of the film." To enable the speed of the projector to be accurately controlled, the Watershed team first fitted it with a pedestal-mounted 0.67kW motor, which was ideal for use in conjunction with a modern variable speed drive.
It was most important, however, that the drive should generate the lowest possible levels of harmonic interference, as this could easily be picked up by the projector's sensitive sound system, which is designed for use with both optical and magnetic sound tracks.
In addition, the drive had to be able to maintain speed accuracy over long periods, without the need for a speed feedback signal.
It also had to be reliable and, because Watershed is a not-for-profit organisation, price was an even more important issue than usual.
After looking at a range of drive products, the Watershed team selected a Telemecanique Altivar 18 drive as the best match for its requirements.
The unit proved easy to install and, with a little help from Schneider Electric's drives technical support team, it was soon set up to satisfy completely the needs of this rather unusual application.
The drive's inherently good EMC performance was further enhanced by using a power cable with an earthed, braided screen between the motor and the drive.
As a result, no problems whatsoever were experienced with unwanted harmonic pick-up by the sound system.
"The Altivar drive not only gives us the accurate speed control we need," said Luton, "it has also enabled us to increase the motor run-up time to 4.3s.
This means that our films, many of which are rather delicate as a result of their age, are accelerated smoothly in the projector, eliminating take-up snatch.
The risk of film breakage is, therefore, greatly reduced, and reel-to-reel changeovers are made much easier." In addition to allowing continuously variable projection speeds down to 16 fps, the Altivar drive has also been configured to allow the operator to select, quickly and easily, precise output frequencies of 49.7Hz and 50.7Hz.
These frequencies correspond to the projection speeds of 24 and 25fps, which are used by modern films.
"The small outlay on the Telemecanique Altivar 18 drive is certainly money well spent," said Luton.
"We're delighted with the results we've obtained, and we're planning to fit another Altivar 18 to one of our other projectors in the very near future.".
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