12 to 120v inverter circuit ?

[[email protected]]

I have a little 150 watt inverter and would like to know more about it.
But trying to go from circuit board to schematic is a lost cause.
Anyone have links to a schematic of these items? Why? I'd like to see
what it would take to run it from 32 VDC rather than 12. Why? To
power it off the 32 volt battery system on a railroad car. Who knows
where it would lead from there ;=)
TIA
Don

 

[Mac]

I have a little 150 watt inverter and would like to know more about it.
But trying to go from circuit board to schematic is a lost cause.
Anyone have links to a schematic of these items? Why? I'd like to see
what it would take to run it from 32 VDC rather than 12. Why? To
power it off the 32 volt battery system on a railroad car. Who knows
where it would lead from there ;=)
TIA
Don

It might be easier to just interpose a DC-DC converter. 150 Watts is only
5 Amperes at 32 V, more or less.

--Mac

 

[mike]

I have a little 150 watt inverter and would like to know more about it.
But trying to go from circuit board to schematic is a lost cause.
Anyone have links to a schematic of these items? Why? I'd like to see
what it would take to run it from 32 VDC rather than 12. Why? To
power it off the 32 volt battery system on a railroad car. Who knows
where it would lead from there ;=)
TIA
Don

Typical current technology inverter uses a dc-dc inverter to generate
about 160VDC, approx the peak voltage of 120V sine wave. This is done
at high frequency to keep the core small.
That's switched thru a FET bridge to generate the 320V p-p.
the pulse width is adjusted so that the RMS value of the waveform
is approximately the RMS value of a sinewave.

All you gotta do is put more turns on the transformer primary and
use primary side switching devices that can handle 3X the voltage. But
there
are probably gotchas. Murphy lives in my basement, so there are
ALWAYS gotchas...
mike


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[kell]

I have a little 150 watt inverter and would like to know more about it.
But trying to go from circuit board to schematic is a lost cause.
Anyone have links to a schematic of these items? Why? I'd like to see
what it would take to run it from 32 VDC rather than 12. Why? To
power it off the 32 volt battery system on a railroad car. Who knows
where it would lead from there ;=)
TIA
Don

I think you can get an inverter that runs off 32 volts.

 

[Paul E. Schoen]

If you take three of these inverters and wire the inputs in series, each
would see about 11 VDC. You could put 12 VDC power zeners across the inputs
to balance the voltages. You could wire the outputs in a sort of three phase
star configuration with a common neutral, but it would not be true three
phase unless you could somehow synchronize the waveforms. For the same
reason you could not connect the outputs in parallel for 450 watts. You
would also need to load each 120 VAC output equally.

Another option would be a simple chopper circuit using PWM at about 40% duty
cycle to change the 32 VDC to 12.8 VDC. You could use a series MOSFET or
IGBT driven by a 555 timer (or a microcontroller), and then an inductor and
capacitor to filter out the high frequency components and reduce the 32 volt
peaks to a fairly smooth DC level. This would probably be cheaper than a
DC-DC converter, and a lot easier than rewinding the transformers.

Good luck.

Paul