A project way above my station so need help

T

TxMan

Transmitter Man
I'm more involved in basic RF and antenna design so I'm afraid this inverter project is way out of my comfort zone.

I hope one of you gents can tell me whether this is feasible and maybe you have a contact of a designer who may be interested in taking on a project.

I am looking for a solid state inverter for use in a automotive installation.

This is a big one, 13.8v DC input and 48v DC at 2.5kW out.

I have a suitable charging system worked out (Electrodyne 350A alternator, adjustable external regulator and a couple of commercial truck batteries + some 4/0 cable).

Your thoughts please (I know I'm probably a little crazy).

David
 
D

Doon

New member
2.5kW? That's almost 230A at 12V assuming inverter efficiency of 90%. The way I see it, you are looking at a complicated set-up with multiple power MOSFETs in parallel arrangements carefully load balanced and switching at the highest frequency you can manage. The simpler and probably cheaper approach would be to come at this from the other direction. Start with a diesel or gas 5kW generator with output at 120Vac or higher and then downconvert that to the desired 48V. Your primary current works out to 22A so you won't need those massive welding cables on the front end, you will be able to use single power MOSFETs rated for 50A continuous current so no load balancing or compensation is required, just make sure your heat sinks/cooling system can take the heat. You will still need to decide on the switching scheme for the high side MOSFETs in the bridge but with single 'FETs you have more options available to you.
 
T

TxMan

Transmitter Man
Hello Gentlemen,

Doon,

I fully understand my suggestion is for a fairly serious piece of equipment but I really don't wish to go the diesel generator route. To large, noisy and carciogenic:)

Large input cables are no problem and nothing new to me 4/0 cable + Anderson connector.

My alternator is an Electrodyne 14V at 350A: www.electrodyne.com

Sandro,

I need more than a schematic but that would be a start to at least get an idea of component cost.

Are you involved in power supply design?

Thanks.

David
 
M

m0gjr

New member
Would it not have been simplier to start out with two 28v alternators in series into two batterys?
 
M

m0gjr

New member
Hmm i could be a little more helpfull than that.

i would recomend using a transformer convertor, a straight boost convertor at that current level would require too much ferrite (think 4 of the biggest cores comercially avalible stacked up)

Use igbts rather than mosfets, 400 amps devices are obtainable so you don't need to parrallel mosfets. However you do it efficiency will not be good. You would be much better off starting at a higher voltage.

There is a reason why trucks, millitary vehicals etc use 28volt dc bus.
 
T

TxMan

Transmitter Man
Hi again Alex,

I only read your first response before just now reading your second.

Yes, I'm aware some commercial and many military vehicles use a higher voltage and I also appreciate this would make life easier but if I went that rout I would use a 48v alternator for this project but at least for the time being I'd like to see how far I can take this with a 12 to 48v converter.

Thank you again for your suggestions.

David
 
D

Doon

New member
You seem to be determined to build this inverter. Have you built custom power inverters before? What about a 48V, 100+A alternator dual mounted inside your truck? Wouldn't that be cheaper and easier?
 
T

TxMan

Transmitter Man
Hello Doon,

In answer to your question and as stated in the title this is not my area of expertise being more involved in antennas and some RF amplifier work.

I have used several high power solid state pure sine wave inverters 3kW plus in the past including one with 12v input. The buss bar on the input was interesting to help carry the current!

Thanks.

David
 
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