Square to Sine Wave

You can't get there from here.

Luhan

If you have a somewhat fixed load at lowish (

As a matter of curiosity, if a device (black box) were available to connect to the output of your inverter and provide a sine wave from the inverter's square wave, what would you be willing to pay for it? And how much power are we talking about here?

I read that series resonant converters are good for upto 20 kW at epanorama. But they are intended for the dc/ac conversion not as an after the fact solution.

Anything at all can be done by finding the right schematic? Make sure it contains a transformer because by the time you attenuate all the high frequency components, your output will be at brown-out level.

Poppycock. A steep (couple pole) low-pass filter will do it.

Delivering a reasonable amount of power through it, at a variety of loads and power factors, and having the inverter appreciate it, is another story completely. ;-)

Tim

If the filter is steep because of notches and the notches are at the odd harmonics, and implemented buy parallel tuned circuits, it may not be so bad.

Prehaps more stages ! 180Hz 300Hz V -----+--))))))---+---)))))---+---)))))---+------+--- Load ! ! ! ! ! ----!!-----+----!!----- --- ) --- ) ! ) GND ! GND

It works at higher frequencies.

By time you pay for the extra parts, a sine wave inverter may look better.

Or, the load regulation will be bad.

XL = 1 ---)))))-----+---- Load ! --- --- XC = 1 ! GND

If you try to unplug the load, the connector will flash over.

I believe my original post was essentially correct. Commercial sine wave inverters use variable pulse width modulation to closely approximate a sinewave. A minimul amount of filtering is needed after that.

Starting with a square wave at some considerable power level, leaves only expensive and impractical options.

In other words, to get there, you need to start from someplace else.

Luhan

How about the simplistic idea of just using a commercial line filter? The original poster did not specify his power level, but Belkin and Schaffner and Curtis (among many others) make one and two stage filters up to 12-15A at 120V for under $50. Doesn't solve the voltage droop, of course, but sure is easy.

-- Regards, Carl Ijames carl.ijames at verizon.net

Interesting idea, but I thought those filters only removed fairly high frequencies? That in itself may get rid of some of the 'noise' that square wave inverters are notorious for.

Luhan

but you can get there from other there.

and

the

I guess you are younger at heart than me, somewhere in the past decade i ceased to consider winding high power inductors fun.