VSD Com Fault

[2571]

Good morning all,
First Merry Christmas, We are working on 200hp Compressor with a VSD. The Display has been logging VSD Com Faults. We had found two broken last night and corrected. The unit is manufactured by Cutler Hammer and the compressor is a Sullair. This morning we come in to the same thing. All of the wire check out good and all of the boards have been removed and reseated. Just was wondering if any one has seen this before. This is my first experience with VSD and need some help. On where to go and what to check. We have only begun communicating the manufacture but as you know, they are not moving as fast as I need them to.

Please help and Thank you
2571

 

[2571]

I meant to say VFD

2571

 

[Skogsgurra]

VFD:s are known to produce lots of EMI. Communication links are usually the first to be hit. What about screening, SHORT ground leads directly to VFD gnd and separating communication cables from other cables?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[2571]

Thank you for the quick response, would it help if I add that the unit is one of two that communicate back and forth to determine which one needs to be primary and which is to be back up. It has been running flawlessly for one year now. What do you mean by Screening?

 

[Skogsgurra]

Shielded communication cable. Also, it may help to connect the two units together with a good ground strap (aka bonding).

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[2571]

The communication cable is shielded. The communication cable is zip tied to side of the four inch flexiable conduit for about two feet would this hurt?

 

[2571]

Spoke with our Tech support and they replied by stating my voltage to the I/O module is too high. It should be between 22 and 24 volts AC. We are currently at 27 volts. They suggested moving the transformer taps from H1 and H4 to H1 and H5. They claimed this would give the secondary transformer and lower primary and the secondary would be between the 22 and 24 VAC required. Does this sound legitimate?

2571

 

[Skogsgurra]

"communication cable is zip tied to side of the four inch flexiable conduit for about two feet would this hurt?"

Sounds OK.

Are the two units bonded? They should be. Having a protective earth running from ground to each unit is sometimes not enough. Heavy EMI at high frequencies are generated by the inverters.

Do you really supply the I/O with 27 V AC? Sounds rather high. Even 22 V AC is high since the AC is rectified and smoothed and will produce around 30 V DC.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[2571]

No the two machine are not bonded together and yes we are at 27 volts at the AC inputs of the I/O module. You are suggesting running a ground wire from one machine to the other VIA their ground terminals. What your thoughts on moving the Trans taps? Tech support claims they seen this several times now. It has always been there fix.

 

[dpc]

I don't see much downside to changing the tap on the control power transformer. It should work fine at a lower voltage. I'm not sure why that would be causing your comms problems, but it should be easy to do and isn't going to harm anything.

What type of communications are you talking about? Serial port, Modbus, discrete I/O?

 

[2571]

Good news,
Correcting the voltage to the I/O module has thus far corrected our problem, when we arrived on Saturday the unit in question was logging error just sitting there. We disconnected power and re-tapped the Trans to H1 and H5 giving us a lower voltage on the secondary. This provided a lower voltage to the module between the 22 and 24 volts the manufacture want and we have had no error. Unit has been setting in stand by all weekend with no errors. Prior to the change it was logging errors at least every 5 minutes or so. Now I have created a second thread for AC to DC converters so I can create a more reliable voltage because our line will drop during the hot summer month and I am sure I will be looking at the low side then.

2571