Inverter 2400w

That being said, most problems from mod-wave inverters are from low voltage peaks, not the shape of the waves. A capacitor does not fix that.
This is also a common problem when using AC power from many types of generator-sets. It's been well known in the solar-electric industry - I assume rbecause that's where people are using this stuff, full-time and dealing with it. Many mod-wave inverters and lower-end gensets make AC power with 140 volt peaks, whereas grid AC usually has 170 volt peaks. Most appliances don't notice that 30 volt peak difference, but some do - and a few won't work at all. What is commonly used to correct the voltage is a voltage-enhance/booster special made just for this purpose. Any solar-electric dealer will have them. Take a look at the "Backwoodssolar" catalog, on-line. Their 10% booster/transformer/corrector sells for around $145 and is rated at 5000 watts. I've seen these fix many problem situations. Just keep in mind that all these "add ons" can add up after awhile.

I promise I won't do that again!!! LOL

T_Bone

"A huge difference between the quality inverters and the cheaper ones is the efficientcy (lower) and idle current draw (higher)."

Very often, that is NOT the case. Most of the high-end full wave inverters are less efficient that the cheaper modified wave inverters. Sometimes less by 5%. Go read the specs on Xantrex/Trace or Outback. I've got several models from both companies and researched it well before buying. My house runs off of stacked Outback full-wave inverters. My cabin runs off of stacked Trace/Xantrax mod-wave inverters. I would of prefered modified wave Trace inverters for my house, but they won't qualify for selling back power to the electric company.

In regard to idle, or stand-by current draw, with most newer units, regardless of price, there's very little difference - except one thing. Some of the better built units, mod-wave or full-wave are load sensing, and can sit in stand-by mode with very little current draw until they sense demand. Also, that demand-sensing is adjustable.

In regard to mod-wave inverters, price and quality. I've got several Trace/Xantrex 2400 watt units (inverter/charger) that cost close to $1000 each. I also have some Chinese Harbor Freight 4000 watt inverters that cost $129 each. The cheap Harbor Freight inverters make power every bit as good as the high-end Trace inverters, and so far have help up very well. I've been using them to run high-draw power tools for two summmers while building a cabin in an off-grid area. I didn't expect much from them at first, but am now pretty amazed at their quality. In my opinion, they are better than some TripLites. I've got a 750 watt (1000 surge) TripLite that I can't stand to use, mainly because the cooling fan runs all the time. My cheap HarborFreight inverters have dual thermal-controlled fans that only come on when hot. If you want to run a good test on a cheap mod-wave inverter - use it on a standard shop-style automotive battery charger. That will tell you a lot. Get a car battery that needs charging. Then hook your charger to it plugged into grid current and look at the rate of charge. Then, try it running off your inverter. Very often, if you get 30 amps while on the grid, you will get 20 amps from one brand MW inverter, and maybe as low as 10 amps from another. Interference is another test. Run a TV a couple a feet from the various inverters - with some the picture will be clear, and with others, it will get interference lines.

For the great info that I can use. Please read my response to B&D.

T_Bone

In regard to smoothing out that modified square wave into a perfect sinewave - I don't believe it would come even close.

That's why Xantrex sells the SW series.

If you check the out put of the UPS systems the others are talking about they also are a modified sine wave.

Scott

John T

Would it matter how large of transformer that I should use for a 3600w MSW inverter?

I"ll probably just use a UPS for the stero equipment as that"s a cheap solution but if a transformer will help the motors and floresence lites, then I"ll put one on the inverter output.

T_Bone

I found a Tripp-Lite 2400w UPS, a pure sine wave UPS that will work just great. The output is 2 circuits of 20a, or more than enough for what I need.

T_Bone

Now, if you put the capacitor in parallel with the load, the capacitance combined with the output resistance of the inverter will give you a low pass filter. The problem is that the inverter was never designed to handle a highly reactive load. The current rush when the inverter switches is not going to be good for it.

As Keith said, if you want to clean up the output you need an LC filter: An inductor in parallel with the capacitor, both in parallel with the load. Ideally the reactance of the capacitor should match the reactance of the resistor. This happens when the frequency equals one over 2 * pi * the square root of the LC product. If my calculations are right, this would mean you'd need a 0.2 henry inductor to go with your 35 microfarad capacitor. Or you could go with a smaller capacitor and a larger inductor.

Better to leave it alone unless you really need a sine wave output.

I happen to know that this T_Bone lives in AZ in the Phoenix area. I don't know if there's a Lane City there, but since I'm already butting in where I wasn't asked, I'll leave it at that.

Merry Christmas, Stan

That's what I get for using the modified form as I thought I was replying to you when I replied to the general topic up top.

I was not trying to ignore you two guys! LOL

Thanks,
T_Bone

Note that the power company's power isn't all that great. Its closer to a sine wave than a modified sine wave, but still has a lot of distortion & harmonic energy.

I've dealt with large power line filters for test chambers, and have never seen one of reasonable size and reasonable loss that would work down to the fundamental power line frequency.

Most electronics will work just fine on a modified sine wave.

Keith

Gerald J.