I'm in over my head, would someone kinly throw me a life ring?

I don't know enough about electronics/electicity to know if I am in the
correct place to seek some help, but if not, please pardon my intrusion.

In the past, I have help clients locate many diverse (read obscure)
devices,products, vendors, technologies,etc.......

Today,I was asked by a client to help him find an inverter that would
convert a 76vDc input to a 110vAc out put. The current draw would be
about 500ma. I know just enough about electricity to know what an
inverter does, but I've never sourced them before. Thie client has an
EAU of 3-5000 units. I've googled (76vdc invert,etc) and found great
sources for inverters to run the coffemanker while you are driving,
however the device I seek has not been found.

 

Did you find this one?

Tom

 

Intrigues me what situation would use 76Vdc (not a multiple of 6, 12, 24
etc)
Is it possible to tap a lower DC voltage and use an off the shelf 12vdc to
110vac inverter.

Regards
Norman

Greg Postma wrote in message ...

 

Oops...http://energy.sourceguides.com/businesses/byP/invert/invert.shtml.


Tom

 

Ya know, the numbers didn't add up, (but what do I know) so after dinner
I called the guy to get more information. The source of the DC power is
6-12v batteries (in series) so the voltage could be anywhere from 72vDC
(6x12) up to 79.2vDC (6x13.2). He picked 76 volts "cuz it's in the middle".

So knowing what I now know, I'm looking for an inverter that can handle
72-79.2vDC input and 110vAC output. The output current will be about 10
amps @ 110vAC. I hope this cleared this matter up.

Some times a client will ask me for a mouse, so I find him a mouse, ship
him a mouse, bill him for a mouse and then I get a nasty email calling
me names, telling me that I shipped the smallest moose the client has
ever seen. I guess today,I've been looking for mouse when the client
wanted a moose.
Thaks
Greg

 

Thanks for clarification, Tom. I looking under my keyboard, behind the
monitor , I even looked in the little cup holder that came in the
computer and I couldn't find. <G> But I bet I can now.....

Thanks
Greg

 

You said "The current draw would be about 500ma. " and now you're saying
"The output current will be about 10 amps @ 110vAC.". This obviously
doesn't add up.

Besides your spec being ambiguous, just do as others have suggested, and use
one of those 12v batteries: why go from 72V?

 

There was a thread not long ago similar to this.
Is it a need to boil a coffee pot in a train engine that prompts this
requirement.

 

Then go back to steam engines, and just use the fire

 

John,

The device I seek is not for me. One of my clients (who has employed my
services many times in the past) asked me to find a source for an
inverter using 76Vdc in and 110Vac out. He said he would need about
500ma. I sent my first plea for help shortly after I spoke with him.
In my second post, I said "Ya know, the numbers didn't add up, (but what
do I know) so after dinner I called the guy to get more information. The
source of the DC power is 6-12v batteries (in series) so the voltage
could be anywhere from 72vDC (6x12) up to 79.2vDC (6x13.2). He picked 76
volts "cuz it's in the middle". After speaking with him,and offering the
same suggestion I received "Just grab 12vDc off one of the batteries and
use a commercial inverter" I was informed that the ONLY source of power
was the 72Vdc. There is no access to any other power.

So.... here we are. I'm still looking for a source of an inverter to go
from 72vDc to 110vAc at about 10 amps. As for the location of where this
is to used, I've got no idea. Could be for making coffee in a locomotive
or powering a microwave oven in the space shuttle for all I know. I
really don't know or care what my clients do with the products I locate,
design or manufacture. Like wise, I don't care what they do with
information I provide when I am doing basic research..... It's really
nunna my business.....

Hope I didn't sound ungrateful for the suggestions made by the group and
I also hope that I didn't sound snobbish or boorish. I just thought
that this project would be simple and it is starting to seem like the
wheel has to be re-invented<g>.

So if any of you kind, bright, energetic, good looking folks have any
ideas that might help locate this elusive "grail" I would be most thankful.

TIA
Greg

 

John, You are correct, originally I asked for 500mA and then after
further questioning of my client, I learned that he misspoke. His
initial request for 500mA will not meet the needs of his project. After
discussion, he informed me that his needs are more like 5-6 amps and I
made the call for 10amps as a safety factor.

So the requirements for the device are nominal 72vDc in, nominal 110vAc
60hertz out, with a capacity of 10amps out. I hope that this clarifies
the needs of this project.

Thanks for your patience
Greg

 

---
Almost. Does he need a sinewave output or can he settle for a modified
sinewave or a square wave?

Also, and I apologize for not asking earlier, does your client have
efficiency constraints?

 

Another "gotcha" to consider. You should also find out if the DC supply
(battery bank) is big enough to power your inverter for the required amount
of time, whatever that is. This is a simplified version of a more
complicated question, but you need to know how long the AC device will
demand current. If the load is 1 Amp for 24 hours, this requires a minimum
24 Amp-hour set of batteries. In this scenario, 12 Amp-hour batteries would
not hold enough charge to power the system for the required time.

 

Then either:
A: Hack the coffee pot to run off 72-79VDC
B: Get three more 12V batteries, put them in series, and in series
with the 72V, for 108-120 VDC and run the coffeepot on DC.

Cheers!
Rich

 

Ya know, I think I like this group<G>
Very Innovative thinking........
I mentioned this idea to my client and after he stopped laughing like
fool, he said he thought that I'd come up with a solution like a 3000
milealong extension cord.....
But I like your idea better Rich
Thanks
Greg

 

Would it be possible to tab in between the battery pile and use a
standard 12 or 24 V converter. Probably a lot cheaper than something
crafted for a specific application.

In addition, 10 A at 110 V is quite a bit of power to sustain from batts
for any length of time. Even with 76 V input, taking into account the
inevitable losses (converters usually have efficiencies of 70-80%), he
will load the battery with almost 20 A. Your client will need rather
large batts and thick cable, too.

 

It's a train.

Cheers!
Rich