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Old August 31st, 2019, 04:34 PM   #1
MTB_Hardtail
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Local Control needed on Powerflex 40

I need to be able to start a discharge belt at the end of our main conveyor, in order to clear product. Normally I could FORCE the run in the PLC logic, but this VFD is controlled by a custom PC, to which I have no code access. My techs are worn out from manually down-stacking product. The VFD gets comm from the PC via Profibus, and a 22-COMM-P card.


I can set default params via Drive Explorer, and it looks like I can tie Digital Input 3 - PIN 7 high (+24v) to get control via the keypad and speed pot. Pic attached. Please advise if this will work, or if I am missing something.


TIA, Jim
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Old August 31st, 2019, 06:21 PM   #2
VAN
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I think you are on to something.

A handful of concerns I would look into.

Safety? Can this kill someone if a new person that doesn't know what they are doing and starts the motor.

Will this throw flags in the PC controlling? Motor shouldn't be running, motor is running, send alarm/fault.

I'm not sure you can do an OR on what starts the VFD. Either the comm card does or it doesn't, but I'm not a drive expert.
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Old September 3rd, 2019, 05:31 AM   #3
ktmtragic
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This should work, another safer option is to use the jog parameter/input with a push button or key switch. You will need to set the jog frequency
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Old September 4th, 2019, 10:32 AM   #4
MTB_Hardtail
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Thanks, That's helpful!

No Safety issue here. I am the building controls lead. My techs are doing PMs on our 300 foot main conveyor. The Jog Function moves the main conveyor, but not the 5 foot discharge bed. This was an oversight by the original designer, and causes much extra work for my techs. So, I just need to manually control during the down time window, while they are jogging the main conveyor.
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Old September 4th, 2019, 12:06 PM   #5
James Mcquade
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I disagree, there is a safety issue.

you need to do a risk assessment first.

when doing the manual jog for the unload conveyor, you need several things.
1. an interlock switch going from auto to unload jog which will lock out the 300 ft conveyor controls.
2. you need indicator lights along the 300 ft conveyor indicating auto and manual unload as well as a signal to the controlling system.
3. you need an indicating alarm buzzer / horn stating that the system is going to start in x seconds in automatic at the unload conveyor. no one will get a surprise on it starting.

james
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Old September 4th, 2019, 01:04 PM   #6
Firejo
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You will no longer have control via the PC anymore, is that going to be a problem?
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Old September 5th, 2019, 02:39 PM   #7
MTB_Hardtail
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Possible approach

My techs are doing the jog when necessary to perform inspections. I might be able to wire the discharge belt Stop Logic into their Jog pendant wiring.


Then I can control speed with the speed pot. The discharge belt would then stop, when they release the Jog button.
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Old September 5th, 2019, 03:07 PM   #8
lstavropoulos
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All safety issues aside (which are not to be taken lightly, as has been stressed in other posts), you would not need to change P036 or P038 from 5 to 0 if you program A053 to 5. It will set the start source and speed source to the local start button and potentiometer on the drive for you when you apply 24VDC (or 0VDC depending on the position of the SNK/SRC switch near the drive's terminal block).


You will have to make sure that terminal 1 is getting 24VDC (or 0VDC depending on that same switch). The PFlex40 has an enable jumper to set terminal 1 to be a programmable stop (ramp, coast, etc.) or coast only (when the jumper is removed). For your needs, I suspect that the status of the jumper is irrelevant. If that terminal is not connected to the appropriate voltage, you will never be able to start the drive. I often see that terminal tied to a controlled output from a relay or PLC to serve as a stop (remove power, drive stops). It's not a true safety stop input, but it generally is used as such when comms are controlling the drive.


If all other parameters are default, then you should be good to go.
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Old September 5th, 2019, 04:31 PM   #9
MTB_Hardtail
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Thanks, Istav!

The exact answer I needed. There is a Run Jumper from Pin 11 to Pin 1 (+24v).


I will run the 24v thru a Key Switch (only I and my techs will have the key) and to Pin 7.
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Old September 6th, 2019, 08:51 AM   #10
lstavropoulos
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That would work. May I suggest a little more complexity? I had a similar situation on one of my machines and I added a control station with two switches and an indicating stack light to let people know the conveyor was in "manual mode."


Is the VFD for the discharge conveyor conveniently located at the conveyor, or is it in a remote location? If it is remote, I would suggest doing what I did, as "Local" requires you to access the face of the drive.


I attached a sketch I made for you with suggestions (pardon the ghetto editing). I would actually recommend reprogramming the drive so that instead of "Local" on the input, you would choose "Comm Port" (6) for parameter A053 and set P036 to 2 (2-Wire control via VFD terminals) and P038 to 0 (speed reference is the pot on the drive).


The goal would be to have a control station at the conveyor with one key switch (2-position, maintained), one selector switch (2-position, maintained), and a clearly visible yellow stack light.


The key switch would be used to select AUTO and MANUAL modes of operation. The key switch will allow the key to be removed only in the AUTO position. When in AUTO, the VFD will receive 24VDC at terminal 7, putting it in "Comm Port" mode, allowing the PC to control it. When in MANUAL mode, the key switch will feed 24VDC to a selector switch and a separate source of 24VDC to the yellow stack light to warn people that MANUAL mode is enabled. Use a separate 24VDC source for the light to ensure that you do not overload the VFD power supply.


The selector switch will be used to selected MANUAL STOP and MANUAL RUN modes of operation. The selector switch will energize terminal 2 of the VFD when in the MANUAL RUN position and de-energize that terminal when in MANUAL STOP position.
Attached Images
File Type: jpg Discharge Conveyor Control.jpg (229.9 KB, 40 views)

Last edited by lstavropoulos; September 6th, 2019 at 09:09 AM.
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Old September 11th, 2019, 05:47 PM   #11
MTB_Hardtail
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Excellent!

Very helpful.
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