VFD - RUN control

aisystems · Jul 17, 2006

I have been trying to find out if I can connect +24VDC Output to terminal 2 (start control) of a powerflex40 drive directly from a flex-i/o module or will I run into trouble with leakage current? I have seen others use a relay and don't know why.

Ken Moore · Jul 17, 2006

Never dealt with the Powerflex 40, but in a lot of cases, the drive has it's own 24 volt power supply, and your output will have a different 24 volt supply, an interposing relay is used to isolate the two power supplies from each other.

aisystems · Jul 17, 2006

The poweflex drives have an option for you to use external supply - you need to remove the jumper between term 1 and 11.

Rube · Jul 17, 2006

Remove that jumper when terminal 1 is used as a stop input. I've never read that you can use an external voltage to control this drive.

aisystems · Jul 17, 2006

I have used an external supply in the past - it shows you in the manual but know where can I find out if a PLC output can be wired directly to the run signal.

Ken Moore · Jul 17, 2006

If you look on page 27 of 152 in this manual: http://literature.rockwellautomation.com/idc/groups/literature/documents/um/22b-um001_-en-e.pdf

You can use an external 24VDC source.
So you would have to connect the DC com from the I/O power supply to terminal 4, and your output according to how the drive should run. Fwd only, fwd & reverse, etc....

mgvol · Jul 17, 2006

There are (2) switches on the drive I/O board; one is for selecting 0-10V/0-20mA for the analog output, the other is labeled "SNK"/"SRC". Place this switch to "SNK" if you wnat to use an external 24 vdc supply.

aisystems · Jul 17, 2006

I know the SNK switch needs to be set and I know you can remove the jumper and put +24VDC on term 1, -24VDC on Term 4 and for FWD control, put +24VDC on term 2. But I always see everyone either using a relay or an isolated ouput relay card to control term 2 - does anyone know any reason for doing it this way and not just using a standard output from a 24VDC output mod such as 1794-OB16 (with all 24VDC from same source)?

CroCop · Jul 17, 2006

aisystems said:
I know the SNK switch needs to be set and I know you can remove the jumper and put +24VDC on term 1, -24VDC on Term 4 and for FWD control, put +24VDC on term 2. But I always see everyone either using a relay or an isolated ouput relay card to control term 2 - does anyone know any reason for doing it this way and not just using a standard output from a 24VDC output mod such as 1794-OB16 (with all 24VDC from same source)?

The Drive creates it's own 24VDC power supply.
Using a relay allows you to avoid tying the 2 24Vdc power supplies together.

DickDV · Jul 17, 2006

Usually, the digital inputs are very high impedance and will not load your PLC outputs noticeably.

If you want to test the leakage current, simply connect a milliamp meter between the drives's +24VDC terminal and the digital input. I would expect it to be less than 10ma.

bernie_carlton · Jul 17, 2006

The powerFlex 40 User's manual on page 1-17 shows the hook-up using an externally supplied 24VDC switch. It mentions that each input draws 6ma. Is that a sufficient minimum for the FlexLogix module?

aisystems · Jul 17, 2006

The 1794-OB16 spec manual states on-state current minimum is 1mA per channel (per channel I believe to be per output). Does it sound like it will work then?

Alan Case · Jul 18, 2006

I have done what your are talking about, feeding a PLC output straight int othe drive. Just make sure the commons are the same or tied together.
Regard Alan Case

VFD - RUN control

aisystems

Member

Ken Moore

Lifetime Supporting Member

aisystems

Member

Rube

Member

aisystems

Member

Ken Moore

Lifetime Supporting Member

mgvol

Member

aisystems

Member

CroCop

Member

DickDV

Member

bernie_carlton

Lifetime Supporting Member + Moderator

aisystems

Member

Alan Case

Lifetime Supporting Member

Similar Topics