High voltage ac to dc converter.
High voltage ac to dc converter.
(OP)
Hi ,
I have 240VAC mains and i need to get this converted to 240 VDC at 60A. Is it possible to just use the high power rectifier diodes constructed in a bridge array, with just one electrolytic capacitor. Thanks
I have 240VAC mains and i need to get this converted to 240 VDC at 60A. Is it possible to just use the high power rectifier diodes constructed in a bridge array, with just one electrolytic capacitor. Thanks





RE: High voltage ac to dc converter.
I don't think that the utility company would thank you for taking enormous gulps of current (a lot more than 60A) every half cycle.
Not to mention the exploding electrolytic!
rgds
Zeit.
RE: High voltage ac to dc converter.
Thanks for the fast response. Is there any other options available?
Thanks
RE: High voltage ac to dc converter.
As this would necessitate using a step-down transformer to start with a lower voltage of about 170V the primary current would be reduced to 60* 0.707 - but that's still about 42 amps! What do you need that amount of d.c current at 240V for?
RE: High voltage ac to dc converter.
There are power factor correcting converters used in power supplies to reduce or eliminate the current spike caused by the simple diode bridge & capacitor approach.
These operate over the complete cycle (or very nearly).
I really don't know much about this sort of thing at the 15kW level, but something like that is probably available.
rgds
Zeit.
RE: High voltage ac to dc converter.
This is to power the utilities of an old boat that uses 240vdc inputs when the boat docks
Thanks
RE: High voltage ac to dc converter.
RE: High voltage ac to dc converter.
If you need this much power then the output capacitor will necessarily be large and therefore expensive. At these power levels anything is going to cost more than a few pounds. So, you need a transformer. I would suggest a three-phase system, if you have that possibility. By using a three phase system and a three-phase bridge rectifier, the ripple in the capacitor will be minimised and the system has some chance of working. The voltage can be set where you need it, and one side of the supply can be safely earthed.
RE: High voltage ac to dc converter.
Thanks for your valuble inputs, probably converting the 3 phase inputs would be easier than single phase as mentioned by "logbook". Thanks old chap.
Joy to you.
RE: High voltage ac to dc converter.
A bridge rectifier is the most efficient rectifier to use, but run from single or 3 phase mains which have the neutral referenced to ground, it will give +/- DC out ref to ground.
As zeitghost said, a single phase rectifier will be gulping several times 60A each half cycle to average 60A out and as BrianG said, you'll get somewhere from 240V to 1.4x 240V appearing as +/-120VDC to +/-170VDC according to load and C.
This load needs 3 phase and a transformer.
RE: High voltage ac to dc converter.
RE: High voltage ac to dc converter.
Personally I would put the money toward a new boat.
Rgds, Boxxy
RE: High voltage ac to dc converter.
I have a 20kv dc generator it is out of an old world 2 electric crain.
whills
RE: High voltage ac to dc converter.
All of you have been so wonderful in providing me plenty of options to go by. Thanks for the great illumination.
Joy to you
Mooimooi
RE: High voltage ac to dc converter.
I have a question. Is either side
of the 250VDC supply on the boat tied
to the ground plate? If so you would
need to use an isolating transformer.
If the end user is protected from
the 240VDC and it's not grounded,
which I will assume for the moment
is the case. I might try an auto
transformer to buck the line voltage
down to where it needs to be, then
follow that with a choke input full
wave rectifier and smoothing capacitor.
Three phase would be best because the
power factor would be very good and
the ripple filtering capacitor could
be small.
If the branch circuit is sized properly,
there is nothing to prevent you from
running a single phase capacitor input
supply after the auto transformer.
A choke input supply would still be better.
But either would violate IEC standards,
so I wouldn't try to sell one of those
in the EU. :)
If you build any power supply with a 60A
250VDC output please use appropriately
rated fuses on both input and output
(This means DC rated fuses on the output.)
Include a disconnect switch to lock out
the AC line feeding the supply too. Wire
wound bleeder resistors with a 50% de rating
factor across the caps are also a must as
is a proper enclosure. A device to short
the output when the cover is removed isn't a
bad idea either.
I'd also want a GFI built-in to the supply
since it's unisolated and used on a boat.
Dockside power may not have this protection.
Most of my work is with 480-600 VAC input
switch mode power supplies with output
power from 10KW and up. Building a switching
power supply with a 250VDC 60A output is
pretty close to some previous designs that
I've worked on. They usually began with a
three phase choke input rectifier. If a single
phase input was required a boost converter
type power factor corrector was employed.
I hope this rambling has been of some help
Best regards,
csharp
RE: High voltage ac to dc converter.
Obviously this boat has some sort of DC generator to supply the power when underway with the engine running, yes ?
Would it be possible to drive this generator that you already have with a three phase induction motor. It might just be a case of shifting a drive belt from the crank pulley of the boats engine to the electric motor when tied up.
RE: High voltage ac to dc converter.
HTH
Rod