Tomorrows Service Call

[ptonsparky]

We installed another vendors Industrial Control Panel. Hooked power and load to it. The rest is theirs.

They have been having some problems with it and are wondering about the 'dirty power' that 480 supplies. ok. They have lost quite a bit of equipment including an HMI, 2 small vfds, a communications modem, a relay and a control transformer. Maybe some others. We found out this morning.

My first thought they should have some line reactors on the VFDs as a minimum.

My question is more on what happened to the HMI. How likely are we to have a problem from the line side of the 480 thru a stepdown control xfmr, a power supply and then to the 24V HMI? Are the 2?HP Schneider VFDs likely to give that much of problem?

 

[GoldDigger]

With an SDS or two involved, I would take a close look at whether or not there are ground offset problems that are affecting data and control wiring between boxes.
Slightly less than optimal installation of VFD output wiring can induce some large voltages in adjacent circuits, possibly even including EGCs.

 

[ptonsparky]

With an SDS or two involved, I would take a close look at whether or not there are ground offset problems that are affecting data and control wiring between boxes.
Slightly less than optimal installation of VFD output wiring can induce some large voltages in adjacent circuits, possibly even including EGCs.

This is all PVC once it leaves the control room so we used drive cable from the VFDs on out.

I did not closely examine their equipment. Sometimes it is better not to, but they are definitely experienced in what they do.

 

[ptonsparky]

Interesting.

The four VFDs, 2-2hp and 2-5hp, share a common plastic wire duct, line and load. Only a couple feet, but also with the 24 and 12vdc. I did not think that was quite right but am not a UL panel builder.
Line side of the drives adds a couple more feet along with the DC.

According to the POCO, fault current available is about 4K at the transformer. Label inside control panel says 10K.

I suggested the separation of 480 from the DC, and moving the Drive cables directly to the drives vs a terminal block. We will see.

 

[ptonsparky]

The panel builder replied with something similar to 'we are using digital signals and not analog, so seperation does not pertain to us'. Why would that matter?
View attachment 16172

 

[Saturn_Europa]

The panel builder replied with something similar to 'we are using digital signals and not analog, so seperation does not pertain to us'. Why would that matter?

I guess they are only worried about induced voltage degrading the analog signal.

Just thinking out loud but have you thought about putting those switches and power supplies on a UPS. They are usually pretty good at cleaning up power. It may not be the solution though.

Post back with what you find. Its an interesting problem.

 

[Fulthrotl]

We installed another vendors Industrial Control Panel. Hooked power and load to it. The rest is theirs.

They have been having some problems with it and are wondering about the 'dirty power' that 480 supplies. ok. They have lost quite a bit of equipment including an HMI, 2 small vfds, a communications modem, a relay and a control transformer. Maybe some others. We found out this morning.

My first thought they should have some line reactors on the VFDs as a minimum.

My question is more on what happened to the HMI. How likely are we to have a problem from the line side of the 480 thru a stepdown control xfmr, a power supply and then to the 24V HMI? Are the 2?HP Schneider VFDs likely to give that much of problem?

.
there isn't any "noise" i'm aware of that will kill a control transformer.
and a relay? burned out coil on an ice cube relay? same kind of thing that will kill a xfmr.

even having 0-20 ma analog controls in parallel for a couple feet probably isn't
going to cause much of a problem.

those things only die from two things that i know of.
too much voltage or too much current. they are just magnetic devices.
the other things dying i'd think would be too much voltage.

so, we are down to too much voltage, as in a spike or surge.
it'd have to be a pretty good one to do all of that.

and, if the relay was killed, it was pulled in, at the time of its death.
so, that's something to look at. when would that relay be energized?
it also tells you it wasn't something that happened in the night, when
the machine wasn't running. the critter was operating when the stuff
got smoked.

 

[ptonsparky]

The equipment runs 24/7. IDK details on any of the failures. The VFDs do have disconnects on the load side near the motors with no interlocks but the guy servicing them knows not to use them to cycle the motor. That may need some additional emphasis.

 

[jim dungar]

The only 'ground' wiring, I can see, is from the CPT 120V secondary and from the VFDs to their field terminal blocks. Is there an EGC associated with the incoming 480V?

 

[ptonsparky]

The only 'ground' wiring, I can see, is from the CPT 120V secondary and from the VFDs to their field terminal blocks. Is there an EGC associated with the incoming 480V?

Yes, there is an incoming power terminal block to the lower left. #10 cu stranded for phases and EG. 20 amp CB ahead of it all.

To the left is a coil of three drive cables that go to the field terminal blocks. Those cables and the incoming power are the only connections we made.

 

[ptonsparky]

There are primary capacitors within a mile or so that switch as needed.

I have installed a line reactor on a small AB VFD in the other building, different much larger transformer and SE, that was bothered with the switching. Overvoltage faults.

 

[ptonsparky]

View attachment 16176
The 2 white wires on the EG bar to upper left. Good practice, PP, or makes no difference? Guessing the secondary bond then the load neutral for the xfmr.

When questioned, my help tells me that is one green wire in the terminal block. Stripped and folded