Drive Control Paper Machine

What drive controls are used in Pulp and Paper application?

𝗦𝗽𝗲𝗲𝗱 𝗖𝗼𝗻𝘁𝗿𝗼𝗹

When in speed control, drive is mantaining the speed using speed feedback. Encoder is commonly used as speed feedback.
Example : Master Drive, which is master for other follower drive, is set to speed control.

𝗦𝗽𝗲𝗲𝗱 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝘄𝗶𝘁𝗵 𝗗𝗿𝗮𝘄 𝗥𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲

Draw is speed difference between sections of paper machine and ussually expressed in percentage of speed increase ratio of current section with previous section.
Operator use draw to make speed faster or slower than previous section. The goal is to maintain good tension on the web.
Draw can be positive or negative depend on strecth or shrinkage of the material.
Draw is the most common control that is used in pulp and paper machine.
Example : Draw reference on Dryer section.

𝗟𝗼𝗮𝗱 𝗦𝗵𝗮𝗿𝗶𝗻𝗴

Load sharing is used to share or balance the torque load, between two or more motor that controlled by separate drive.
Example: Load sharing betwen Top Roll Press and Bottom roll Press.

𝗧𝗲𝗻𝘀𝗶𝗼𝗻 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝘂𝘀𝗶𝗻𝗴 𝗟𝗼𝗮𝗱 𝗖𝗲𝗹𝗹

Used to control the tension using load cell as tension feedback.
Example: Tension control on Backing Roll Coater.

𝗣𝗼𝘀𝗶𝘁𝗶𝗼𝗻 𝗖𝗼𝗻𝘁𝗿𝗼𝗹

Used when wants to mantain the position or to prevent slack on the web.
Example : Position control for web loop between Heavy Duty Press in Pulp Board Machine.

𝗧𝗲𝗻𝘀𝗶𝗼𝗻 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝘄𝗶𝘁𝗵 𝗧𝗼𝗿𝗾𝘂𝗲 𝗙𝗲𝗲𝗱𝗯𝗮𝗰𝗸

This tension control use torque feedback from drive as tension feedback.

𝗧𝗼𝗿𝗾𝘂𝗲 𝗖𝗼𝗻𝘁𝗿𝗼𝗹 𝘄𝗶𝘁𝗵 𝗦𝗽𝗲𝗲𝗱 𝗟𝗶𝗺𝗶𝘁𝗮𝘁𝗶𝗼𝗻

In Powerflex Drive, it is called SLAT ( Speed Limited Adjustable Torque)
In this control, drive is using Torque setpoint as reference and overspeeding is prevented during web break.
Example: Torque control used in Reel.

𝗦𝗽𝗲𝗲𝗱 𝗗𝗿𝗼𝗼𝗽

Droop is commonly used when the motor current can go too much high, when the speed is faster than other drive that shared the same load. Droop function automatically reduce the speed reference, when there is increase in motor current.

𝗢𝗽𝗲𝗻 𝗟𝗼𝗼𝗽

This drive control does not use speed feedback. Drive could be set on volt per hertz mode or in sensorless vector mode.
Example : Open loop control on Paper roll guide etc.

Additional control is 𝗦𝗹𝗮𝗰𝗸 𝗧𝗮𝗸𝗲 𝗨𝗽.

Slack take up is used during start up of paper machine. When section tension is extremely loose, slack take up is used to speed up that particular section.
Slack take up, basically, just add temporary large enough speed offset to speed up the section, so it can keep up with the rest.