Start Stop VFD via Speed Reference
Start Stop VFD via Speed Reference
(OP)
I would like to start and stop a PowerFlex 40 with a 4/20ma signal.
Can this be done?
Is it a bad (stupid/won't work/troubleshooting nightmare )idea to use the PowerFlex40 24vdc internal power to source transducer?
Thanks
Can this be done?
Is it a bad (stupid/won't work/troubleshooting nightmare )idea to use the PowerFlex40 24vdc internal power to source transducer?
Thanks





RE: Start Stop VFD via Speed Reference
I would check very carefully before using the internal 24 V supply. It can not deliver more than 100 mA and part of that current will be used for the digital I/O. Also, most 4-20 loops are supposed to be floating - taking the supply from the drive itself means that it isn't floating anymore.
Could work, but you need to do some checking on your own.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Start Stop VFD via Speed Reference
RE: Start Stop VFD via Speed Reference
As to whether or not the PowerFlex40 has those capabilities, A-B should be able to tell you. But be prepared to give them a credit card for an answer.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: Start Stop VFD via Speed Reference
You could use an external 'trip amplifier' to give you a relay contact which opens at 12mA and recloses at 16mA and use that to control the drive start input.
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If we learn from our mistakes I'm getting a great education!
RE: Start Stop VFD via Speed Reference
Bill
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"Why not the best?"
Jimmy Carter
RE: Start Stop VFD via Speed Reference
Over here that's what we know as a 'trip amp'. Guess it's a British name.
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If we learn from our mistakes I'm getting a great education!
RE: Start Stop VFD via Speed Reference
On the other hand it looks like two votes for the same device by whatever name.
Bill
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"Why not the best?"
Jimmy Carter
RE: Start Stop VFD via Speed Reference
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If we learn from our mistakes I'm getting a great education!
RE: Start Stop VFD via Speed Reference
I am sure the ABB drives have that feature. Not sure about AB.
RE: Start Stop VFD via Speed Reference
Thanks DickDV.
RE: Start Stop VFD via Speed Reference
RE: Start Stop VFD via Speed Reference
On the PF 4, 40 and 4M, you have a 4-20mA and 0-10VDC input. Since your analog signal is 4-20mA, you would naturally want to use the 4-20mA input on the drive, but that's not necessary. Drop your 4-20mA signal across a 500 ohm resistor to develop 2.0-10.0 VDC. Then use your drive's 0-10VDC analog input for speed reference. (This will be thrown off just a tad; the drive's input impedance is around 11k). By now you're asking "why?".
Dig into the PF drive's Advanced parameter group and look at A055 [Relay Out Select]. Option 10 - "Above Anlg V". Using this option, you can set up a threshold switch using your analog as a trigger. Your threshold is then adjustable via A056 [Relay Out Level].
Once you've got the threshold switch setup, you can drop the Relay's NO contacts across Digital input 1 for 2-wire start stop. With a little trimming on the Analog offsets, scaling values, etc, you can nail it down to perform very accurately.
*Poof*. Now you've got a legit start/stop and speed reference using just a 4-20mA. I've done this several times on various projects; works like a charm.
RE: Start Stop VFD via Speed Reference
I still am not sure why people intentionally use AB stuff.
Yaskawa P7, IQpump Controllers(a awesome drive for pump applications) and even the lowly Altivar 21 have this functionality built in without all the hurdles.