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How To Configure The PL/X Diameter Calculation Blocks

The PL/X reel diameter calculator, taper tension calculator and torque compensator blocks are intended to be used in order to provide automatic current limit control against reel diameter when applied to a center winder having a constant field motor, either shunt wound or permanent magnet types. Please note the technique only applies as described to shunt wound, constant field motorsused on center winders! Different approaches are needed for field weakening or series wound machines or surface winders – these applications are outside the scope of this description. Please also note that I have referred throughout this description to a rewind – the technique can equally well be applied to an unwind.

Disregarding losses, material tension is proportional to diameter times torque – in other words, if constant material tension is required it is necessary to linearly increase torque (current limit) against diameter. For example – if a reel is to build up by a ratio of 10 to 1 (300mm core size, maximum built diameter 3000mm) the current limit has to increase by the same ratio against diameter in order to achieve constant tension as the reel builds up.

Before configuring the blocks you should ensure that basic PL/X calibration and commissioning is carried out. Importantly, measure the surface speed of an empty core and ensure it is the same as or greater than the line speed against the full line speed range. Typically, the rewind would take its speed reference from a preceding drive such as a nip, or from a tacho mounted on a material transport roller – this aspect needs to be attended to first, arranging that the rewind drive receives a 0 to 100% speed reference depending on line speed. The universal input (I have assumed UIP4 is being used for the purpose) can be scaled and offset to achieve this if necessary.

It is important to remember that in order to be controlling torque it is necessary to saturate the PL/X speed loop – in other words you need to make the winder core surface speed faster than the material speed. Assuming that the basic calibration and commissioning has been carried out, this aspect is dealt with later in this description.

Three inputs to the PL/X are needed (or two, if automatic taper control is not required – more on taper later in this description). I have assumed you will be using UIP6 as your tension demand input and UIP7 as your taper demand input, if needed. Alternative inputs can be used, just modify the relevant parameters in the following instructions accordingly.

Please refer to the block diagram in section 3.8 of the PL/X applications manual as you follow this description. The description is written as if the configuration is being done via the drive MMI – the connection can also be made using Pilot or Savvy software, in which case ignore references to setting CONFIGURATION, ENABLE GOTO,GETFROM and make the various connections directly with Pilot or Savvy.

1)Diameter calculator block (top right of the block diagram).
This block is responsible for calculating the reel diameter. It does this by knowing the material line speed (referred to in the block description as WEB SPEED) and it’s own speed ( referred to in the block description as REEL SPEED). Dividing WEB SPEED by REEL SPEED gives diameter. This calculated diameter value is internally connected to the other blocks, but the block still needs to be activated by setting it’s GOTO to some unused parameter. This is the case with any block – a block is not active unless it’s GOTO is connected somewhere, this avoids unnecessary use of processor cycle time. To give the diameter calculator block the necessary signals proceed as follows:



This connects the line speed into the diameter calculator block. Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 1 and set it’s GOTO to 485)DIA REEL SPEED IP and it’s GETFROM to 131)SPEED FBK MON This tells the diameter calculator what the rewind speed is.

Go to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 2 and set it’s GOTO to 26)RAMP INPUT and it’s GETFROM to 485)DIA REEL SPEED IP This tells the rewind what speed to run at – the extra speed demand needed to saturate the speed loop is added later.

Go to CONFIGURATION, BLOCK OP CONFIG, DIAMETER CALC GOTO and set to 300)ANALOG POST 1 (or any unused parameter – this activates the block). You will also need to tell the system what your diameter ratio is – for example, a 10/1 build up ratio requires 486)DIAMETER MIN to be set to 10.00%, a 4/1 build up requires 486)DIAMETER MIN
setting to 25.00%

2)Taper tension calculator block (middle left of block diagram).


This is your tension demand input, and needs to be 0 to 10V or similar – you can scale and offset
the UIP if needed.


This is your taper demand input – taper is the action of reducing the tension away from the ideal of constant against diameter – for example to reduce tension at the end of a roll and reduce the possibility of crushed cores, starring or telescoping reels. It is not always needed on a rewind, and never needed on an unwind. You have the choice of linear or hyperbolic characteristic, see section for more detail. If you don’t need taper, just ignore the above regarding UIP7 configuration.

Go to CONFIGURATION, UNIVERSAL INPUTS, UIP4(T4) SETUP and set it’s GOTO to 514)TENSION DEMAND IP. This both activates the block and connects the block output to the losses compensation (or torque compensator) block.
3)Torque compensator block (bottom of block diagram).

This block allows you to compensate for mechanical losses such as stiction, friction, inertia etc. and the actual settings needed depend on the machine losses – a full description of each can be found in section 3.7. These settings are best made empirically – the default settings will be good enough to start with, unless accurate tension control is critical. Usually applications requiring tight tolerance on tension would employ a closed loop system rather than a predictive one in any case. In order to connect the block, go to CONFIGURATION, BLOCK OP CONFIG, T/COMP +CUR LIM GOTO and set it to 89)UPPER CURRENT CLAMP. For completeness, also go to CONFIGURATION, BLOCK OP CONFIG, T/COMP -CUR LIM GOTO and set that to 90)LOWER CURRENT CLAMP. If the preceding basic calibration and commissioning resulted in the core surface speed being faster than the line speed, all that is now necessary is to go to APPLICATION BLOCKS,
TORQUE COMPENSATOR and set 518)TENSION ENABLE to ENABLED. Alternatively, if there is a need to saturate the speed loop because the core surface speed is the same as the line speed an esay way to do this is to connect the JOG terminal 32 to +24V – this puts the drive into “slack take-up” mode, adding 5% to the total speed demand courtesy of 39)SLACK SPEED 1. Conveniently, this allows you to set 518)TENSION ENABLE automatically to enabled by going to CONFIGURATION, JUMPER CONNECTIONS, JUMPER 3 and setting it’s GETFROM to 714)IN SLACK FLAG and it’s GOTO to 518)TENSION ENABLE.

Once the above has been followed, go to CONFIGURATION, ENABLE GOTO,GETFROM and set to DISABLED. Then perform a PARAMETER SAVE.

Please note the above procedure relates to a very basic rewind – features such as under/overwind, how to configure for flying splice etc. are not covered. Further assistance can only be given if all required machine operating parameters are known.


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