VFD AC/DC supplied
VFD AC/DC supplied
(OP)
Sirs
Can I connect two 5,0kW VFD (diode front end) to a selectable (open transition) AC 3ph or a DC from battery bank?
Fuse protection and blocking diodes at DC entry. If yes, which should be the DC voltage compared to AC?
Could the built-in precharge be used for both supplies? Control power to be adequately selected.
Thanks
Can I connect two 5,0kW VFD (diode front end) to a selectable (open transition) AC 3ph or a DC from battery bank?
Fuse protection and blocking diodes at DC entry. If yes, which should be the DC voltage compared to AC?
Could the built-in precharge be used for both supplies? Control power to be adequately selected.
Thanks





RE: VFD AC/DC supplied
Maybe if you fully described what you want to accomplish and what you have to work with, we can help further.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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RE: VFD AC/DC supplied
Direct input to DC bus is well known, some VFD models are designed to receive it.Others, don't. Existing installations would require modifications of standard equipment.
The specific question it was related to the possibility of DC connection directly to 2 AC entry phases. The rectifier diodes (two of them) would be overloaded if output load was kept but with load reduction (speed, for example) maybe it would be possible an emergency power supply from swgr battery banks to drive important motorized valves, flaps, safety doors, etc during AC shutdown. Some details as control power, alarms, interlocks would be considered. It makes sense? Are my assumptions correct?
Thanks again.
RE: VFD AC/DC supplied
Another issue is if the VFD monitors the supply for phase loss or something.
Keith Cress
kcress - http://www.flaminsystems.com
RE: VFD AC/DC supplied
reason is the the diodes are of course current rated: you will be putting 1.4x LESS current thru those 2 diodes for the same output rating since your input voltage is 1.4x higher, even tho you lost the 3ph sharing of 1.73, so current will only be 1.73/1.414 = 22% higher.
Example: 10a ac rms *1.73*230v rms rated input = 3979 watts in. put in the 330vdc instead and it will be 3979/330vdc = 12 amps
Hence, you should be fine on current rating on any but the cheapest Chinese import drives.
RE: VFD AC/DC supplied
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD AC/DC supplied
Damned lack of edit function vexes me here....
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: VFD AC/DC supplied
It is just a cheap alternative power supply idea without large modification in existing equipments.
I will prepare it for some few special equipments.
Maybe it can be used in an emergency situation. When you agree as in this case, I feel more confident.
Thanks again.