12 volt to 240 inverter with 10-25% duty cycle
12 volt to 240 inverter with 10-25% duty cycle
(OP)
I am looking for help designing a 12V dc to 240v AC 60 or 120 Hz 1000W inverter whose duty cycle is only about 10-25%. The load is purely resistive.
Ed
Ed





RE: 12 volt to 240 inverter with 10-25% duty cycle
The Chinese-origin stuff is available for a fraction of what you would spend on developing your own.
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If we learn from our mistakes I'm getting a great education!
RE: 12 volt to 240 inverter with 10-25% duty cycle
RE: 12 volt to 240 inverter with 10-25% duty cycle
240 volts and 60 Hz is the standard in some localities, but it's not as common as 240 VAC/50Hz or 120VAC/60Hz.
1000 watts is at the high end. You'll be drawing about 100A at 12 volts. It's do-able, but requires heavy gauge wiring on the DC side.
120 Hz? Where did that come from?
RE: 12 volt to 240 inverter with 10-25% duty cycle
Higher frequency 120Hz= smaller transformer.
I assume the reduced time on will be reflected in my DC power draw.
The efficiency of my device (emitter) is much higher at 240V but there is a thermal (power dissipation) limitation.
Ed
RE: 12 volt to 240 inverter with 10-25% duty cycle
We made our assumptions because the word and the phrase used have accepted definitions within a range of trades. By the way, commercial inverters may use step-up frequencies up to and beyond 20 kHz in order to reduce the size of the magnetics; 120Hz magnetics are not substantially smaller than 60Hz magnetics.
You seem to actually want a pulsed DC output with variable pulse width at an increased voltage. Or I may be misunderstanding you.
Please try to specify your desires with more precision and detail, without misappropriating standard industry terms.
Mike Halloran
Pembroke Pines, FL, USA
RE: 12 volt to 240 inverter with 10-25% duty cycle
Emitter is one end of a bipolar transistor (emitter, base, collector). You probably mean source, a word that can mean the opposite of sink.
120 Hz is not a standard frequency. So you're unlikely to find an off-the-shelf transformer designed to optimise its capabilities at 120 Hz. 400 Hz is standard in aircraft - so there are plenty of transfomers optimised for 400 Hz. Basically, the standard power frequencies are 50, 60 then 400 Hz. If this is for ground equipment, then you would never be bothered with the extra mass.
How many of these do you require? If you only need one, then you would cobble together some test equipment - perhaps being stymied only at the actual 1000 watt output stage. At this sort of power levels, you'll need some on-site help.
RE: 12 volt to 240 inverter with 10-25% duty cycle
I want to do this from a 12 volt battery and I thought an inverter circuit approach would be more efficient. Efficiency is key.
By emitter I mean photon emitter.
60 or 120 Hz does not matter.
RE: 12 volt to 240 inverter with 10-25% duty cycle
Photon emitter? Light bulb?
May I ask why you need to start with a 12 volt battery?
RE: 12 volt to 240 inverter with 10-25% duty cycle
And I'll vote with VE1BLL, is there a good reason you need to power this from a battery?
RE: 12 volt to 240 inverter with 10-25% duty cycle
I need 240 Volts for 1.25mS @120Hz and 0volts for 7.1mS
12 volt battery is all I have avaiable to me in this remote location.
Ed
RE: 12 volt to 240 inverter with 10-25% duty cycle
Add a full wave rectifier to charge a capacitor to the peak to peak voltage. This should get you to about 240 VDC.
For your 1000 Watt load that's about 4.2 amps.
I = C * dV/dt, so a 470uF 400V cap will have a little over 10 volts droop in 1.25 mS. If that's too much, double the capacitor.
To switch the current, maybe a hefty MOSFET or IGBT...
Watch out for ripple current in the capacitor and the fact that this is a lot of dangerous power and voltage to be throwing around.
RE: 12 volt to 240 inverter with 10-25% duty cycle
There's about a hundred things that can go wrong with this sort of project. If you're not going to bring in a on-site expert, at the very least wear safety goggles to save your eyesight when the capacitor bank explodes.
RE: 12 volt to 240 inverter with 10-25% duty cycle
You really want to take 12VDC and convert it to 240VDC and then repetitively switch the 240VDC so it is on for 1.25mS and off for 7.1mS.
You will likely have to build a boost stage to produce a 240VDC bus and then use a MOSFET or IGBT to switch it on and off.
RE: 12 volt to 240 inverter with 10-25% duty cycle
RE: 12 volt to 240 inverter with 10-25% duty cycle
It works very well. Much better than other waveforms or DC.
RE: 12 volt to 240 inverter with 10-25% duty cycle
Dan - Owner

http://www.Hi-TecDesigns.com
RE: 12 volt to 240 inverter with 10-25% duty cycle
RE: 12 volt to 240 inverter with 10-25% duty cycle
is it :-
a) a spiral tungsten filament, takes a cold surge current
b) Modern IR LED technology more like a laser
c) a true pure resistance ( Measure resistance ?)
Switching a DC rail on/off is much easier than amplifying a Square
wave !
RE: 12 volt to 240 inverter with 10-25% duty cycle
Perfect advice.