Drive Digital Input Wiring

Hello,

I am hoping someone can give me some insight on the current wiring of some AC drives we are currently using.

A bit of a background. We are currently starting to experience failures on some of the drives in a 20-25 year old panel. The Current mix of drives are Mitsubishi Z260's , AB Bulletin 1333, and newer Mitsubishi A560 AC drives.

We have limited spares and its getting harder to source the same drives.

Within the next 2-3 years were are planning to do a complete control systems upgrade, so I'm looking to replace a few of the existing drives with a more modern/common drives we are using elsewhere in the plant to keep us running until the upgrade as we don't know which vendor platform we will be going with.

I was planning to use AB PowerFlex 70's.

Now, onto my burning question.

The existing drive's digital inputs (both Mitsubishi and AB) are "sinking". Our PLC provides a relay contact for FWD/REV jog commands to each drive. What the original designer did was tie all the digital input commons together. Now, the AB drives's have 5 VDC logic and the Mitsubishi's have 24 Vdc logic. Is this a common practice? I personal don't see this too often. I have attached a very simplified drawing to show what I mean.

My worry is the interfacing wiring for the PowerFlex 70. It says the digital inputs can be either sinking or sourcing, but I'm leary of connecting the commons together of 2 of the new and old drives.

I hope my question makes sense. Maybe I should ask simply, can you time the common of different voltage DC supplies together when using sinking digital inputs??

Hope my question makes sense. If not, please let me know and I'll try to clarify...

Thank you,

Andrew

I'm not sure you would call it common practice as who knows why the variation in vendors for the VFDS, but it might have been the only method to wire up the drives. You didn't mention the make of your relay card, if your drawing is accurate the COMs would need to be tied together.

An new control system and it's IO might provide you multiple commons at the relay card which you could isolate. I don't see the danger as along as you configure the new drives to be of the same sinking configuration. Most drives have jumpers, or such to change the mode.

As for your drives, those A560s are 2 generations old now. Mitsubishi is onto the 800 series drives. For the most part the A800 will be a drop in replacement, for the 500, you can get an optional terminal adapter plate to re-use the wiring terminal block from your A500 drive. Makes it easy to swap the drive.

Thank you for the response.

Hi Paully,

Thanks for getting back to me. To answer some of your questions:

a. The drawing is correct. I was actually trying to draw a simplified version for conceptual reasons. In the existing wiring, the commons are tied together, as per the drawing - wiring is done on the drive's common terminals.

b. The relay card is a AB 1746-OW16

c. I know the history of the mis-mash of drives. Orginal canimet had Z260's and Bulletin 1333's. Z260 became obsolete, replaced with A560's. Now the A560's are obsolete. We are now just going to replace with a more common current drive for us until we upgrade. That's all. We have other FP 70's, so sparing up as of right now makes sense for the time being.


So, to sum it up, I could replace an existing drive with one that has sinking inputs as long as the commons are tied together (as they already being done)?

Thanks,

Andrew

Just an opinion, but I would not go to the PF70 if it were me, unless perhaps they are all 230V? If they are 480V, just go to the PF753s now. The way they get people to switch is to immediately start raising the prices on the older versions when a new version becomes available. They already did that on the PF700s, the only reason it hasn't happened on the PF70s yet is because it's the only drive available in 230V over 30HP. Once they release the 753s in 230V next year, the PF70s will start down the road to that great electronic heaven in the sky... Sure, it may take another 10 years, and maybe that doesn't matter to you. But once that's fixed, expect the price to jump.