Posted 17 May 2008 - 10:36 AM
I have an application Welding Set, on which I have to install a VFD. Welding Set is 200kva 415V, 2 phase input. Power Supply is from Generator which has a 3 phase output. Presently without a VFD, the Welding Set creates unbalance load at the Generator. I think that if VFD is installed in between, the problem of unbalance load can be solved. My worry is that since only 2 phase output of VFD will be used, will the VFD trip on motor cable open at output?
Has anyone installed a VFD in such application?
Posted 17 May 2008 - 08:51 PM
My answer would be No, I have not done this and I do not think that it will work.
A VFD is designed for a three phase load and connecting a sigle phase load across two phases will not yeild the correct waveform and current in the load, plus I would expect that the inverter protection would not be happy.
You would probably be better looking at some form of UPS which is designed for this type of operation.
As a thought, if you are concerned about the loading on the generator, why not look at a transformer with a delta primary and a star secondary on the output of the generator. This would help to even up the load a little.
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Posted 19 May 2008 - 03:24 AM
As marke said I feel same thing. No VFD will support such application. A very basic version of inverter(unlike Vector control etc) may work .
But then too, whenever your transformer does welding work, your dc link will be dipped. And very next instance when the welding is off there will be over voltage on the Bus. So the capacitor will be under heavy charge discharge cycle. And very soon they will bust.
May be the IGBT support for this.
I think this may work with current source inverter.
In one of the Ac drive (Mostly Simovert P or A from siemens) I have seen drive works even one arm is disconnected at the output.
But balancing the the impedence is certainly not possible.
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