VFD Start Circuit

[powersoff]

I have 8 VFD's that are going to be controlled via Hand Off Auto switches.
Is it "better" to use a external 24dc power supply for start circuit?
Or should I use each VFD's supply?
The VFD's will be mounted adjacent to each other and have a common stop button(via relay).

 

[itsmoked]

If you use an external you have a single failure point. Generally this isn't desired. See, if the external power supply fails - everything goes down.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

I would use the 24V from each VFD and also keep them isolated from each other. You'd hate to have a ground fault loop cause odd issues or a fault in one unit damage other units.

Peter

 

[ScottyUK]

The on-board 24V is usually low power and not especially well protected, so if you are taking the signals out into the field I would use an external supply or use interposing relays to protect the expensive drive from the actions of well-meaning fault-finders. If the 24V signals will remain withing the panel I'd use the on board supplies.


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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

And if you needed to run those signals out into the field then an individual external supply for each one might be in order.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Slight aside: one of the things I like about the old A-B 1336 drives and others of that vintage is that the I/O was on a discrete card, so if maintentance techs did something untoward then it blew the I/O card rather than wiping out the drive. Alas the days of discrete cards are largely behind us. That said, an I/O card for a 1336 cost more than some modern drives so maybe I shouldn't complain too much.



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If we learn from our mistakes I'm getting a great education!

 

[jraef]

So true. I get caught in that same nostalgia trap sometimes. For example I used to recommend to people that they not use the PID functions inside of a VFD and instead, use an external PID controller because if anything went wrong with the VFD, you don't have to reprogram the PID loop. But last week I bought a little 1HP 230V VFD for a project, I paid less than I paid for a PID loop controller! Copy and paste the VFD settings via the comm port and voila... up and running.

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