Regarding the PM 51, Holmens Bruk says:

"We we re the first mill in the world to in stall apaper machine
incorporating an overriding digital-control system."

This was 12 years ago and, since then, pure analog systems have not been considered for our purpose. For the
Braviken mill we had the choice of an overriding digital system and ASEA's direct digital system.

We selected ASEA's direct digital system."

"By using a digital-control system, web breaks due to draw variations eaused by the motor drive have been
practically eliminated. "

"The con tro l system of the sectional drives can be more or less forgotten and therefore more time can be
allotted to the monitoring of other sousces of fauIts."

"The digital system has a very high degree of availability."

"The reproduceability ofthe web-tension settings shortens the start-up time
following a web break."

"The test panel of the digital system enables the servicing team to maintain
contact with the drive system via analog instruments, such as recorders, etc."

The PM 51 produces approximately 500 tonnes of paper (45-49 g/m-) per day and is attended by
only 5 persons/shift. The speed and draware measured with ASEA's patented digital speed­
feedback system. The web-tension is measured by a number of PRESSDUCTOR@load cells
placed at strategic positions. Given the speed of the pope drive, the microcomputer of the controi
system can calculate the length of paper in a reel.

The controi system is designed using microcomputer techniques. The microcomputer is a version of
ASEA' s industrial computer, DS 8. Other versions of this computer are used for the operating
equipment of the motor drives and for sequential events recording.

Operation is supervised and controlled from two control rooms, one for the PM 51 and one for the
two winders. (780903)