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Quincy Qsync Compressor VFD error "L2 Phase Problem"

mrq11

Plastic
Joined
Aug 10, 2020
Hello all,

New poster (long-time lurker) here looking to pick your brains on my Quincy compressor.

First off, specs:

Quincy Qsync Twin Screw Compressor
50 HP
Mfg Date: 2004
Model #: QSYNC50ACA14A
480v 3ph
73,000 hours

The compressor is inside an air-conditioned plant, with metal mesh filters on all air inputs. All maintenance performed on schedule.

Drive:
Siemens SIMOVERT VC Drive
Model Number: 6SE7027-2ED61-Z

With that out of the way, I am having issues with random shutdowns and the error "Phase L2 Problem."

This has been going on for at least 2 years, but recently the shutdowns have become more frequent with it shutting down twice or more in one day. We have talked to Quincy, they won't touch it (The software is gone and no way to download it from the drive). They did look at the voltage for over two weeks and no abnormalities were present. The tech said that these compressors are usually kaput around 50,000 hours.

I talked to Siemens, they no longer support the drive or do any work on it. The manuals just state that there is a certain board that "may" be the problem, along with two others.

Does anybody have any advice on what I can do to fix this issue? This is the main compressor for our whole plant, my backup can barely handle the plant air requirements, so I really need this fixed.
 
It appears you may be able to download data from the drive with the Siemens software. There's RS232 in the front panel connector but it has a custom pinout see manual).

Check the basics first: disconnect the motor and megger to ground. Check windings are all continuous and the same resistance. Check none of the supply legs sag when loaded (I assume this has already been done). Check all terminals are tight and show no signs of heat.

Is the error on the drive or the compressor controller itself? If it's on the compressor itself, I suspect the issue is with those boards, not the drive. I doubt the drive has a high level interface to the controller; it'll just be a fault contact on something of that age. It may have per-phase voltage and even phase sequence monitoring if they used the same board for DOL compressors.

Check that the currents in all three input phases are equal, along with all three output phases.

If there is no high-level interface, and it's the drive that's throwing the fault, you may well be able to reverse engineer the programming and replace the drive. It's questionable if it's worth that for a compressor that the manufacturer has said is 50% past normal lifespan.

One other thing to try: rotate the phases, i.e. L1>L2, L2>L3, L3>L1. Do this separately for both the motor and the incoming power. See whether it stays L2 or shifts to another phase.
 
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One other thing to try: rotate the phases, i.e. L1>L2, L2>L3, L3>L1. Do this separately for both the motor and the incoming power. See whether it stays L2 or shifts to another phase.
Good plan, but L2 for Siemens would only refer to the incoming phase, the outgoing would be U, V, W in any error code. Don't bother swapping the output phases.

Siemens are one of the most complicated VFDs on the market, and it doesn't help that the Germans quickly abandon old products and move on.

Is that EXACTLY what the fault displays as? Or does it say "UCE Ph. L2"? Because "L2 Phase Problem" is not listed as a valid fault message. If it is the UCE fault, the UCE is the collector/emitter for the IGBT transistor firing board on phase 2. The board that does that either fails or not, so intermittent tripping with that is often indicative of a loose board or connector inside of the drive. You should try opening it up and checking all of the connections, ribbon cables and board edge connectors.

If that error is coming from the QUINCY panel and not the drive display, then you need to get Quincy involved.
 








 
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