# controlling paper tension

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#### Endy

In controlling the paper tension system,there always use a brake at the unwind side. Is there system use a motor to replace the braker? In this case we use different motor's speed to make the paper tension increase or decrease, and the last we can control it. What the different between use braker system and use motor system? What the advantage and the lost from each system?

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#### Koen Verschueren

If you want to use an electrical motor to control paper tension you can use a 4 quadrant frequency convertor (or use a brake resistor). In this case you can control the tension in the paper more accurate than with a normal mechanical brake. You can also consider using an hydraulic pump mounted on the shaft that support the paper roll and control the pressure with a proportional valve.

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#### Hakan Ozevin

You can consider using a Torque controlled drive, i.e. current (tension) is constant and speed is variable. This solution is more dynamic compared to mechanical/hydraulical solutions.

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#### Michael R. Batchelor

Don't know about paper system, but I've seen motors used on mylar tape and monofilament lines. My guess would be that the advantage is the motor bearings should exhibit less wear than brake shoes.

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#### Chris Harper

I agree that you can use a motor in torque mode as a brake. One option for braking is magnetic particle depending on size of application. This is best. Limited on heat dissapation. If too small then motor in torque or air brakes are your options.

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#### Jeff

You could try and use two electric motors in a bus connected drive configuration,ie the motor braking the paper roll supplies waste energy to the rewinding motor. The two converter drives need to be matched together and configured so that the sum energy used by the operation is very small indeed, however the braking motor may need external surface cooling if used at a reduced speed for long periods of time.This system has the advantages of low power consumption, simplicity, no need for friction brakes,reduced maintenance as there are no parts to wear out and very accurate control of the web. A good type of drive in ac or dc configuration are available from Eurotherm drive systems.

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#### Charlie Griswold

Brakes are genearlly cheaper than motors, that may be the difference. For material being pulled in, with large forward momentum, brakes would work. With lighter material, or in controlling at lower speeds, motors are better because you can control the tension in the feed material more accurately.

Charlie Griswold

S

#### Sameer

Dear Sir,
There is no need of any mechanical brake. Pickup an AC drive and operate this drive in TORQUE MODE/TENSION MODE. Here Speed will depend upon the Paper pulled. However, please make sure that there is min.force reqd. to move the shaft of the motor. If Gears are coupled at the shaft end, then the motor shaft will not be free & therefore the Tension mode will not work.
If the motor shaft is not free You can use a PLC & adopt some formula so that speed is proportional to the wraps of the paper(unwound at the unwinding side & wound at the winding side), which will again be proportional to the DIAMETER of the PAPER REEL.
Thanking You
Regards
SAMEER

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#### Jack

Have used motor for tension control in a steel-strip pickling line. Used a 4-roll bridle arrangement to allow backtension and controlled strip tension with the unwinder in torque control. GE Innovation drives are pre-packaged for this kind of control.

N

Best solution is using brush motors.They are better then other motors. See some documentation for them- there are 2 type: 1. for positioning 2. for speeding . Best Regards, Nenad M. [email protected]

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#### Nicholas J. Baranyk

I'm no Paper Mill Expert by any stretch of the imagination, but while you can, in fact, use a Motor to control Unwind Tension, it's an expensive approach.

DC Control is the most cost-effective approach, but it's not as simple as throwing, say, a Reliance Electric Flex-Pack-#3000 and an RPM-III Motor on the Unwind Stand and calling it a day. Rather, you have to understand that the Tension requires accurate, dynamic control: I.E., you can't set the Drive for X RPM, and think that you're done. Rather, that speed, and resultantly, the re-gen currents must, in fact, vary, as Core Diameter reduces.

My recommendation: Get a Reliance Electric Sales Engineer in to see you, and discuss your ideas. He'll, most-likely, point you toward a Web-Pack-#3000 Solution, which is a Flex-Pack-#3000 with some very sophisicated Winder Algorithms. You'll need a "Dancer" Pulse Encoder -------- no biggie, as I'll bet that you're running a Dancer Tach. right now to vary the tension with the Brake.

One last thing: you need to know that a Motor/Drive Controller Combo. isn't cheap. A 50-hp. solution will set you back a clean $25,000.00 if you go DC. Figure somewhere in the$40,000.00 range for an AC Solution, and bear in mind that I haven't included Engineering Services.

Let me know if you want additional support. I can accommodate you from some more simple advice to fee-based services.

My E-Mail: [email protected]

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#### Michael Yukoweic

Please note That the unwind break you mentioned is controlling variable diameter roll of paper, ypur torque / rpm requirements fluxuate proportionally with the diameter.It may be helpfull to simplify this by applying your tension through a set of fixed diameter nip rolls. the tension and speed is measured up stream from the nips. if you need additional explanation [email protected]

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#### Daniel Veillette

A motor give you the advantage of higher ramp speed to accelerate, as the system work in motor mode in order to accelerate and then start reducing the amount of power transfert to the unwind and at the end of the accel curve act as generator.
You get also better control on the unwind inertia as the parent roll change in speed and in diameter. Controling the inertia give you a feedforward control on sheet tension.

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#### Johan Bengtsson

What you do when you have a motor is that you actually run it as a generator. You run it in "torque control" and it will get whatever
speed the paper gives it and the torque does of course match a certain tension given the current diameter of the unwind side.

The energy you get out could be used to help feeding the pulling motor, thus saving energy.
If you use a brake this energy would be "lost" as heat.

/Johan Bengtsson

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