problem with vfd interference

[joe magee]

I started a rack today. I have an e2 rx and bx and a Danfoss 5000 drive on my condenser.The problem is when I put the drive in inverter mode I loose my io boards. and the rx can't see the bx. I changed out the inverter to no avail. When the drive is in bypass all the boards come online. I called danfoss and was told to ground the 485 center com which i did. the filter on the drive is enabled. The one thing I do notice is when the ground from the condenser to the rack is disconnected the boards go on and off when I reconnect it just the bx goes off line. Any suggestions would be helpful. Everything is grounded well. I'm wondering if I'm getting any backfeeding any where.

[Brian_UK]

Are there any 'shielded' cables in the system which have been grounded at both ends? If yes then remove one end otherwise the shield acts as an aerial.

Can you change the frequency that the inverter operates at? This can be a source of problems on some systems.

[joe magee]

The shield is grounded and I removed it to no avail. I changed some parameters on inverter. No luck

[750 Valve]

Are there any 'shielded' cables in the system which have been grounded at both ends? If yes then remove one end otherwise the shield acts as an aerial.

Can you change the frequency that the inverter operates at? This can be a source of problems on some systems.

By this I think he means the switching frequency, usually max setting 4.0 khz, try dropping to 3.5 or down to 3.0 - the drive may start to squeal more and the motors will quieten.

Sounds like your backfeed is caused by bad shielding or poor cabling,
is data (digital I/O, 0-10V signal, RS485 or Echelon cables) run parallel to mains cabling - especially cabling from the output of the drive? Big no no
Are the power cables screened going to the condenders from the filters? not necessary but good practice
Are these cables grounded at the VSD end on the grounding plate Danfoss supplies with a clamp setup around the braid? very necessary
Are the low voltage/data cables screened and earthed at the mount supplied by Danfoss as well? all should be
Is the filter earthed properly? should be
Are the Echelon and/or RS485 cables' shield run to earth at the E2 end?
Are you using echelon I/O cards or RS485? Coz if you have RS485 then it should be earthed in EACH E2 at one end of each I/O network and then the main echelon loop earthed at ONE end only - this means only one E2 either RX or BX. But if all cards echelon then one loop with one earthed end only.
If echelon is the cable up to CPC spec? Is the cable up to any spec? coz poor unshielded cable = headaches

[joe magee]

Turns out that the cat 5 cable from the bx to the rx was run in pvc pipe next to the high voltage line of vfd. We ran in metal emt a different way and it worked fine.

[Frigidsicle]

This sounds like a wal-mart rack. We have been having a lot of installation problems with the VFD commisioning projects. Of course when your performing upgrades like these on 400 stores per year you are bound to hit a snag ever so often.