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Idothewires

Siemens S7-1200

11 posts in this topic

I have an application that I am working on that I would appreciate some help with.  The idea is to speed up and slow down a VFD at a predetermined footage increment.  For example, the operator would set the limits of this increment on the HMI, say 9'' to 10''.  Now the motor would start to ramp up starting at 9'' and reach max at 10'' then ramp down to 9'' again.  Then repeat.  Also I would like to display the ramp progress on the HMI.  Would there be a particular function block that I could use for this? Any help with this would be greatly appreciated. 

Edited by Idothewires

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Can't help without more info. 

How is the VFD controlled?  Analog, network, digital IO?

How does the PLC know the length?

What kind of HMI?

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Crossbow,

The VFD would be controlled through the analog output on the PLC(Siemens Simatic S7-1200).  The PLC gets its length signal from an encoder.  The HMI is a Siemens KTP 700 Basic.

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The S71200 has technology objects for position control. Have you looked in to that ?

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jrw,

Not yet.  Would this be where I accomplish this task?

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Posted (edited)

Yes. You can do point to point moves with a TO in the 1200. That’s the way I would control it. 
I can’t say I understand your ramping scheme but a 1200 can be a position controller 

Edited by jrw

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Ok jrw,

I looked into technology objects.  What I gather so far is that TO's need to be used with either servo motors or steppers.  What if I just want to control a third party VFD in open loop? 

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Posted (edited)

So analog to your drive and high speed counter from an encoder back to the 1200 hsc input

Easy

This is done with a TO

A third party drive will work just fine

Enable from plc - a Qx,x output

Analog reference from plc  for position/speed control

 

motion1200ana.jpg

Edited by jrw

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there is no encoder on the motor there is an encoder on the line for footage that's it.    

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Posted (edited)

It doesn’t need it on the motor. 
Setup the mechanics appropriately. The plc closes the position loop. 
But the motor must drive the material and the encoder must be driven from the material. They have to be connected in some fashion. 
Do some reading. It will work. 
Or hire a system integrator. 

enc.jpg

Edited by jrw

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