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Unread December 3rd, 2019, 08:56 AM   #16
kvogel
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Quote:
Originally Posted by TWControls View Post
The current drive isn't capable of PID. Only a basic speed reference so in the best circumstances the dancer bounces up and down while it runs.
You would need a controller (PLC or Web controller) to process the signal from the dancer and send an analog speed signal to the drive.

Last edited by kvogel; December 3rd, 2019 at 09:02 AM.
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Unread December 3rd, 2019, 12:40 PM   #17
GaryS
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Originally Posted by TWControls View Post
If running in torque mode, do you need a speed reference from the main line?
the speed reference dos not need to come from the line speed but you will need a speed reference from some place even if it's just set at max speed
I line to use the line speed and scale it in the drive to be just a little faster then the line speed that way it keep the speed from running away if there is no load
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Unread December 3rd, 2019, 03:35 PM   #18
Helliana
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Also, please note that reels have a maximum speed at which they can rotate. Be sure you cannot physically get to that limit under any circumstances, such as the dancer gets tied up and the PID loop runs away. Can't tell you how i know this.....
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Unread December 3rd, 2019, 03:56 PM   #19
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Originally Posted by Helliana View Post
Can't tell you how i know this.....
You can't or wouldn't or would just rather forget it happened
We have all been there at some time or other at least if you have worked in this industry for a while
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Unread December 3rd, 2019, 04:43 PM   #20
OkiePC
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Quote:
Originally Posted by rdrast View Post
It hasn't been said here that I saw, but when using a dancer to tension a wire, I much prefer to use the dancer to control the drive in torque mode, not speed mode. A PID in a PLC is generally good enough for this, or a stand alone card if you like, or one in a drive.


Why torque mode? You are controlling tension. Tension is directly relatable to torque, and far less likely to get into heavy oscillation. It also eliminates a control loop (speed loop) in the drive. I took a bunch of payoffs and takeups on wire drawers out of speed mode, and put them in torque, and eliminated blowing fuses daily.
I worked with same payoff systems for a product that was being pulled by a downstream roller. The torque reference for the payoff roll was in the reverse direction and did a good job of keeping constant tension on the fabric. Basically we were using the motor as a brake for most of the cycle, and as a motor when threading up a new roll.

There were some complexities to it when the roll went empty. We had a sensor to detect that and switch the VFD to speed control mode. We also had to cycle the VFD enable bit to allow the control mode to be switched. That particular drive did not allow switching on the fly between speed control and torque control. If we left it in torque mode, even if we changed the torque reference to a really low value, the motor would gradually run away at full speed.

I am not sure how torque control mode would work if you are driving the product off of the reel into a dancer...seems like the torque to let off product would not be consistent enough to deliver wire at a steady speed.
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