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About nebiter

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  1. Control panel testing

    Well, it seems to be OK so far. I energized the panel without any drive fuses closed and the panel control circuits drew about 0.4A of 120VAC. Then I de-energized, closed the fuses to drive#1 and re-energized and it came up and I was drawing 2.5A. I then powered down and closed the fuses to another drive and current draw went DOWN to 1.9A! I powered down again and closed the rest of the fuseholders, powered up and current draw is 3.75A. I don't have any sensors attached yet, just the 1.5KVA xfmr, my 240W 24VDC supply, Compactlogix PLC, 15 inch Panelview (on 24VDC), e-net switch and the eight (!) A-B 525 drives. The drives are all 5HP and less. CLX IO light is steady so it must see the drives. Time to fire up RSLogix and take a look. This is definitely more tech-friendly than bringing 480/3Ø into the shop that someone might trip over or drop something sharp on. Current at 3.68A now and fairly steady. Time to get to work.
  2. Control panel testing

    No these drives do not have separate control power, the manual says: "Three-phase input provides full rating. Single-phase input provides 35% rating on three-phase drives" So single phase should be no problem for the drive and there is not an input phase loss parameter to enable/disable. I'll give it a go and report back.
  3. Control panel testing

    Yes they are individually fused. I am pretty sure that I would not be able to put any of them to run mode, but just to see the e-net work with them all and the settings are all good would be great before applying 480 to the box. I think I'll put a fuse on my test line cord going in and also my clamp amp to see what is going in. Might be a useful technique.
  4. Control panel testing

    " Don't you have separate protection to isolate the devices on the 120 volt secondary? " Yes, the secondary is fused, that would be backfed too. In the other direction, the zero wire is fused, it being fed in the forward direction to energize the control components. The idea is to just tickle the drives enough to allow the PLC to see them without bringing in several amps of 480VAC/3Ø. 
  5. The control panel is wired, the PLC and HMI far enough along to get the thing energized and start debugging. The primary power is 480VAC/3Ø and there is a 1.5KVA transformer for control circuits, chemical pumps, sensors, etc. The usual method is to open the fuse to the transformer primary and use a suicide cord to energize the 120VAC circuit and get everything working. There are no motor loads connected to the panel, it is still in the fab shop. If one were to close the transformer primary fuse and backfeed the transformer, one could generate a bit of 1Ø/480VAC to turn on the VFD's and include them in the configuration and final programming of things without bring in 480VAC/3Ø of primary power, eh? Good, bad or indifferent?
  6. In using pressure switches to monitor for pump failure, what would be the plusses/minuses to using Normally Open vs. Normally Closed contacts of the switches themselves? The only difference I can see would be the open cicuit fault where using open on rise connection would not sense an actual pressure loss and using close on rise would transfer to lag pump then (shut down?) alarm needlessly when in fact pressure is OK. Is it a toss of the coin or is there a real difference? My company has always used open on rise apparently just because thats the way we've always done it. Comments please?