analog trim of AC drive line speed

i had previously posted asking if anyone has ever used a analog type sensor as a trim type dancer for the line speed of a AC drive.
I got some good advice, but thought it might be best if i posted with a seperate post about using the analog sensor to trim multiple AC drives.
Machine we are working on will now utilize a analog sensor as a dancer type configuration to trim the line speed of multiple AC drives. I had originally been told only one of the drives would need to be trimmed (have not actually seen the machine), but now being told by our Director that he wants this analog sensor to trim multiple motors.
Confused on exactly how to feen a analog sensor into the plc and have it trim a scaled output to the drives for the required line speed. I understand how to scale the trim analog value in to represent a value of 0-100% that could then be used to multiply by the original value out to a motor, but confused on how to read that value in and if analog trim sensor in the middle which is 12ma and how to use any value below 12ma to lower the line speed and anything above 12ma to increase the line speed a percentage of lets say +- 20%.
Any suggestions would be greatly appreciated. At the moment pretty confused on which direction to go with this.

I would suspect that you really want to feed the analog sensor into each drive, individually. Perhaps some sort of signal multiplexer..1-in, many-out..to isolate and amplify.
Running things into and out of the PLC might work, but remember that the PLC is a digital device, and, as such, has time delays in processing anything. The delays of retransmission might cause headaches, depending upon the line speed of the web. If the web is slow, and if the accel and decel are long, using the PLC will work.

Thanks JD
that was what i was thinking would possible be the best. Have you ever used a device that would take the analog input from a sensor and give multiple analog signals out that could connected into multiple drives. I have never used anything like that. Any suggestions? I will do a search on the internet but if someone has already used this type of device and had great results and would share which one they used would be great. As everyone on this site in a big time crunch on this and that is what is so great about this site.

Haven't used these, but if the drive can accept a 4-20mA input for trimming, then it may be worth a look.

http://www.laurels.com/qls.htm

Here you go , these are old school textile line control guys
http://www.carotron.com/systeminterfacecomponents/sontracgen/
They have all kinds of interfaces

The cheap option if you just have a few drives is to wire the analog inputs in series. You will have to work out what the resistance of each input is and make sure the sensor can drive that. (eg. AI on VSD = 100 Ohm, sensor can drive Max 750 Ohm, so can wire max 7 drives in series)

Note this only works for mA Analogs.

I haven't been able to find anything to fanout an analog voltage, so here is a schematic if you want to create your own board.

This one's response time for full deflection (going from 0-10V) will be around 33uS.

I need to back up for a moment. What type of process are we looking at? Meaning, where is the loop you're trying to control? I'm just not seeing the need to trim all the motors.
If it's a feeding application, then trim the feeder.
If it's a winding application then trim the winder.

The only thing I can think of for trimming multiple motors is if the material flow is from one processing machine to another (I don't know what your processes are, so I can't really go much further with this line of thinking).

Thanks for all the replys. I always print these post as pdf files and save for future reference, great site.
When i got home last night and able to get away from actual work ( i know a lot of you know what i mean by that) and was actually able to do some research i found this on the pheonix contact web site.
https://www.phoenixcontact.com/onli...id=2864794&library=usen&pcck=P-13-01-02&tab=1

Looks like it may be a good device if you only have one extra analog out but need to send it to a couple of different devices.

It is for trimming the feeder motor. The machine is actually a dual type machine with two seperate sides that perform the same operation. A feed (Nip) motor on each side but only has one plc and one extra analog output. The plc is a microloigix 1400. I was going to add another analog card but the machine builder did not leave any extra room. Breakers etc. are all the way up against the side of the plc so trying to use the one analog out. Machine is in El Salvador and i have only seen pictures at the moment and the thought of getting in El Salvador and having to redo the whole cabinet to make room for another analog card is not very tempting.

JordanCClark said:

I haven't been able to find anything to fanout an analog voltage, so here is a schematic if you want to create your own board.

This one's response time for full deflection (going from 0-10V) will be around 33uS.

I need to back up for a moment. What type of process are we looking at? Meaning, where is the loop you're trying to control? I'm just not seeing the need to trim all the motors.
If it's a feeding application, then trim the feeder.
If it's a winding application then trim the winder.

The only thing I can think of for trimming multiple motors is if the material flow is from one processing machine to another (I don't know what your processes are, so I can't really go much further with this line of thinking).

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