VFD Application Question
VFD Application Question
(OP)
I have a VFD driven motor on a dredge and the only available supply in the area is 13.8 kV. One design was to provide a 13.8-4.16 kV step down power transformer ON THE DREDGE and then from there it would supply the 4.16 kV VFD and Station Transformer on the Dredge E-House.
I was thinking a different way to save some transformer cost and footprint. This is to supply 13.8 KV and will be connected to a 13.8kV Switchgear in the dredge and the VFD will have a 13.8-4.16 kV isolation transformer internally and the station transformer will be 13.8kV-600V. This will save us the cost and footprint of having a separate 13.8-4.16kV transformer on board the dredge. Is this possible? Did anyone have this arrangement with dredge supplier before?
I was thinking a different way to save some transformer cost and footprint. This is to supply 13.8 KV and will be connected to a 13.8kV Switchgear in the dredge and the VFD will have a 13.8-4.16 kV isolation transformer internally and the station transformer will be 13.8kV-600V. This will save us the cost and footprint of having a separate 13.8-4.16kV transformer on board the dredge. Is this possible? Did anyone have this arrangement with dredge supplier before?





RE: VFD Application Question
But be that as it may, I'd rather see the isolation transformer for the VFD be dedicated to the VFD alone and the station service be an entirely different dedicated transformer, rather than a shared 4.16kV transformer feeding both loads. My reasoning is, if the VFD does something horrible to the transformer and blows the primary fuses, you lose the station service as well. Murphy's law dictates that this will happen on a dark and stormy night, leaving the dredge crew in total darkness.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: VFD Application Question
RE: VFD Application Question
RE: VFD Application Question
So what is the type of 4.16kV VFD you are going to use? If it is a "transformerless" design like a Rockwell PF7000 CSI drive, then I see the viability of the way it was proposed originally, in that you are not duplicating the 13.8kV switchgear and you reduce the size and weight of the transformers. But if using a multi-pulse VSI drive design that will need a separate transformer feed anyway, then adding another step-down transformer ahead of it would be redundant, so your proposed alternate would make more sense as long as you can incorporate both the step-down and multi-pulse designs into one unit.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: VFD Application Question