dc/ac inverter

[nescafe]

1.) How to change this design to 72V input

2.) If i look at the data table that is presented on the web page,
4500W should be reachable with 72V. This is too small for me.
I need to get 8kw at 72V input (i have battery bank 72V-135Ah)

http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/

Can someone help with redesign ?

 

[ehsjr]

1.) How to change this design to 72V input

2.) If i look at the data table that is presented on the web page,
4500W should be reachable with 72V. This is too small for me.
I need to get 8kw at 72V input (i have battery bank 72V-135Ah)

http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/


Can someone help with redesign ?

Yes - don't do it. Your battery is too small (see
<http://en.wikipedia.org/wiki/Peukert's_law> ) for
anything but brief use, and the design is not intended for
8kW per the url you posted. The transformer won't handle it,
and the pass transistor design is wrong (no emitter resistors)
to start with, even for 4.5 kW. If you went with the design,
you'd likely have to double the # of transistors and the size
of the heatsinks. With no emitter resistors you could easily
burn out the transistors. And good luck on designing and winding
a suitable transformer based on that url. You'd also need heavy
cables - better would be large copper bus bars - between the
battery and the input of the inverter. It is just not
practical.

What is the application? How long do you need to provide power
to it? You might be better off buying a generator, or tripling
the number of batteries to get 216 volts DC and running the
application from that, provided you need to run the application
for only a short time.
Then there's the matter of re-charging those batteries ...

Ed

 

[mike]

1.) How to change this design to 72V input

2.) If i look at the data table that is presented on the web page,
4500W should be reachable with 72V. This is too small for me.
I need to get 8kw at 72V input (i have battery bank 72V-135Ah)

http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/


Can someone help with redesign ?

First, I'd worry a LOT about that design. Has a lot of issues that
could turn it into a pile of smoldering metal.

Second, You don't day what you're doing with it, but
I'd be wary of trying to get 100A reliably out of a 135Ah battery.

You might be happier splitting the load, if you can, and using multiple
smaller inverters.

 

[tm]

Assuming 100% efficiency, 8000/72 = 111 Amps. Your 135 AH batteries
won't like a 111 A draw if it goes no very long. Presumably, the current
would actually be a bit higher.

Jon

Not only that but you will not get 72 volts at 111+ amps.

tm