RE: Converter to change modified sine wave to sine wave?
One of the differences between a low pass, and a band pass, is that if you design a band pass filter with a high enough "Q" (Narrow bandwidth) it will ring like a bell.. And as you know if you strike a bell (A real bell) with a hammer the sound can continue for quite some time (Depending on the size and quality of the bell).
Now imagine if you kept hammering on that bell,
A low pass filter.. Does not ring like that (There may be a tiny amount of ring but not enough to make a difference) So you need a nice tight bandpass, very high Q, in short,, A bell.
Take a hint from someone who has actually done this kind of work for a living. You need a little more knowledge and a little less technical sounding lingo. This is not kHz or mHz circuits we are talking about. This is 60 hertz.
The frequency does not really matter since filter design really depends on reactive impedances which are a function of frequency and inductance or capacitance. The only difference is that the inductors and capacitor values get bigger as you design for lower frequencies but frequency and time domain characteristics apply for
all frequency ranges as long as you are talking about lumped element filters.
Dick
RE: Converter to change modified sine wave to sine wave?
If you do a Fourier transform on a square wave you find that it is composed of an infinite series of odd harmonic sine waves with decreasing co-efficients.
See HERE
I suspect that by the time enough of the harmonics are removed with a filter to get a pure sine wave or anything close to one, there will be very little power left - not enough to provide anything usable.
There is a nifty animation showing the way the square wave is generated by adding odd harmonic sine waves HERE
As I recall the third harmonic of a square wave is down 13 dB from the fundamental and the other harmonics go down in amplitude as the harmonic count goes up. The harmonics follow a sin x/x amplitude. The fundamental will be the largest component in the Fourier series but as I indicated you might have to bring the amplitude back to 120 V RMS with an autoformer due to elimination of the higher order harmonics.
Dick
RE: Converter to change modified sine wave to sine wave?
With the voltage peaks of the starting MSW being a nominal 140, IMO a perfect filter would yield a sine wave with 140 volt peaks, or 99 volts RMS. A further complication is the behavior of MSW inverters varying the peak voltage and pulse width as the RMS voltage regulation method. A good filter would totally defeat the inverter's voltage regulation. The output voltage would be directly proportional to the DC input voltage, which typically varies by at least 10%. So you might be looking at an output voltage range of roughly 90 to 100. With that in mind, I think even a good filter is infeasible for the application.
.
Please explain more about how a MSW regulates the AC output voltage. I would expect the peak voltage and positive and negative pulses to be constant duration regardless of load just like a sinewave inverter. A DC to DC converter would exhibit a varying pulse width based on load as you described.
Dick
RE: Converter to change modified sine wave to sine wave?
A three pole L(series) C(shunt) L(series) low pass filter would go a long way in reducing the higher order harmonics which would result in a much smoother waveform. You could also try a 60Hz bandpass filter design as an alternate trade solution. The design challange would be to hold the insertion loss to a minimum. That would require large low resistance inductors and some analysis would have to be done to see if the rms voltage was still at acceptable levels after filtering. There would also be some concern about how the inverter would work with the harmonices being reflected back into the inverter. This would be an interesting Spice analysis. You might have to follow the filter with an autoformer to get the voltage levels back if the filter reduces the amplitude too much. This would imapact overall efficiency but that might be an OK trade.
Dick
RE: How many really miss mowing the lawn?
I take pride in the way my yard looks. I trim with a push mower, weed eat around all the flower beds and walks, and then jump on the 0 turn mower to finish. Do this at least every 5 days. Would not have it any other way. ;)
I agree except I do use a self propelled mower and don't need a riding mower. Very rewarding and relaxing.
Dick
RE: Battery
Not using furnace...roughing it out! Haha.
I have a Honda eu1000i and found out a bit ago battery checked out fine!
No space for second battery.
Might make it to Sheridan WY tomorrow. Hopefully an RV dealer can be found, if necessary.
Sigh.
How warm is the thermostat overnight? Put it down closer to 60-65 (or less) (or off)
The 7155 is a slow charging converter. What generator do you have?
You should make it with one group 27 but you need a better charging system.
Consider getting a 20 to 40 amp portable charger and if there is space for a second battery get it.
You should be able to go a full day with a healthy Gr 27 battery if you are only operating the basic fridge, water heater, water pump and some lighting. We dry camp for a full week with a single Gr 27 in the Smokies and run the Fantastic vent fan all night long. We charge with a Honda Eu 1000 for about 3-4 hours each morning and the battery charge current drops off from 10A (starting charge) to 3A by that time indicating that it still had plenty of capacity before starting to recharge. Our trailer parasitic current draw with the fridge and water heater on but no lights or other accessories on is on the order of 0.5 A so that is only 12AH per day
If you are going to be dry camping you really need to consider purchasing and learning to use a clamp-on Ammeter to check your parasitic current draw and charging current. Knowing the battery voltage is only half of the information you need to manage your 12V system. Sears carries a nice DC clamp-on that should work well.
Dick
