Are you using the phrase "duty cycle" in a strange and unusual manner? In the normal use of the phrase, 50% would be more than sufficient to cover off the requirement of 10-25%. I suspect that you need to clarify exactly what you're referring to; is it the waveform itself?
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.
I am using 50% as the standard square wave, which can be observed on a scope, 50% positive saturation 50% negative saturation or 50% on 50% off. I want a pulse on (240V) for 15% of the time and off (0V) for 85% of the time and I want the efficiency of an inverter.
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.
When you used the word 'inverter', we assumed you wanted pseudo-AC out, near some standard line frequency. When you used the phrase 'duty cycle',we assumed you wanted something that could provide rated power for some stated period, with 3x longer rest periods of zero power output to cool off. As opposed to 'continuous duty', which has enough thermal dissipation to not need rest periods.
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.
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.
Descriptively I guess I want a pulsed dc output. I can get what I want from my HP signal generator. I set it for 6oHz, square wave, 10 volts P-P, and it puts out a symmetric square wave and indicates a 50% duty cycle. I then select the variable duty cycle mode and reduce it to 15%. I can then use an amplifier to boost the voltage to 240 volts P-P.
I want to do this from a 12 volt battery and I thought an inverter circuit approach would be more efficient. Efficiency is key.
It sounds like you want +120 volts at 8.33 amps for 15% of the time (1.25 mS at 120 Hz) and -120 volts at -8.33 amps for 85% of the time (about 7.1 mS). Yes?
And I'll vote with VE1BLL, is there a good reason you need to power this from a battery?
If one looks *inside* an off-the-shelf inverter (12Vdc to 120 or 240 Vac), there's a possibility (depending on the architecture) that you might find a high voltage DC rail.
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.
A "pure resistive" IR emitter is still just a light bulb with a filter. There are easier ways to control power to a light bulb. Is there some reason you must have a specific pulse shape?
Clues about the resistive load would be nice
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 !
