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Author Topic: What can be run with a square wave?  (Read 3639 times)
Barn Owl
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« on: February 22, 2008, 03:33:59 PM »

I have an old 12v square wave trip-lite inverter, and I believe it also has the battery charger function. It came with my bus but was never hooked up. Question: What can you run with a square wave? Is it worth the trouble? What kind of problems could I encounter?
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« Reply #1 on: February 22, 2008, 03:45:38 PM »

Barn Owl,

I am sure looking forward to hearing the answer to your question.  Originally, I was told that TV would have lines and any AC motor would be burned up when it tried to start.  Since I have heard many say that their TV worked well and had no lines.  Others have said the use their modified sine wave to run their air conditioner while underway.  I don't know what the answer is to these "seeming" contradictions bnut I am all ears.  Do you think it depends on each different inverter.  I have heard absolutely no complaints about "Pure Sine Wave" inverters failing to do anything.

Me too,

John
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« Reply #2 on: February 22, 2008, 03:58:04 PM »

The old square wave inverters will play hell with a lot of electronic devices.  The modified sine inverters work a lot better because they  break the leading and trailing edge of the square wave into steps.  Battery chargers that are light weight meaning they have no transformer will usually go up in smoke instantly on a true square wave.  Both square wave  inverters and modified square inverters can be much improved by the addition of a isolation transformer in between the output of the inverter and the load.  As simple as I can say it.  My .02  John
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cody
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« Reply #3 on: February 22, 2008, 04:46:28 PM »

As soon as you plug in the square wave inverter the cost of fuel will double and women and children will weep and rend their clothes, the sun will fail to appear and the civilized world will shudder to a stop, the sun will no longer shine.  The way my luck runs none of the beautiful women will realize that the end is near and fail to rend any clothing, or worse, libby will see me taking pictures of it. Yikesssssss, ohhhhhhhh the humanity.
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« Reply #4 on: February 22, 2008, 05:05:45 PM »

My understanding is that most inverters on construction sites running saws, drills, etc are of the sq wave or modified sine. They use them because they're considerably less expensive initially, not because the civilized world will come crashing to a halt and women will be throwing themselves into your arms, that sounds too much like a dream LOL Wink
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boogiethecat
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« Reply #5 on: February 22, 2008, 07:29:19 PM »

"by the book" you can run any electric motor that has brushes (drills, saws, etc), or anything resistive (lightbulbs, electric heaters that don't have motors) on a square wave inverter.

Any motor that does not have brushes will get a lot hotter than normal due to the way it treats harmonics (makes heat out of them instead of rotating motion) Not saying it'll kill 'em, but they definitely won't be as happy as if run on a sine wave.

Square wave or modified square wave inverters will definitely interfere with electronic things, wireless computer accessories, motosat reception, TV's etc.  Although most electronic things these days with switching power supplies won't get "killed" running them on a square wave inverter, many won't function properly. Computers are an example... some are fine, some aren't.

All of this is direct experience of mine, as both a bus nut who has tried them, and as an electronic engineer.  My personal take? Toss the square wave and modified square wave inverters and use pure sine inverters, or do it some other way.  These days pure sine isn't all that expensive, and the potential problems you'll never have to solve are worth it.

Just my 2c

Boogie
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1962 Crown
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« Reply #6 on: February 23, 2008, 07:18:03 AM »

Seven years ago I started with a Tripp lite inverter, as far as inverting it did everything I needed to do. The reason I replaced it was like most lower priced inverters it had a low amp charger, took tooooo loooong to charge the batteries.
 After a year I replaced it with a trace Dr3624 Modified Sinewave Inverter for the three stage charger. It has been running air conditioner, computers, I have Streets and Trips GPS hooked to my computer, works fine also Sprint aircard, printer, refrigerator, lights fluorescent and halogen, electric shaver, vacuum cleaner, microwave convection oven,  ignitors for LP cooktop,electric pencil sharpener, ceiling fan, LCD TV's, DVD and VCR etc. I also use it to charge various brands of  cell phone and power tool batteries. In 7 years I have replaced the circut board on a 10 year old furnace and the circut board on a 10 year old airconditioner.
 The negatives are the clock on the microwave goes berserk on inverter power, however the timer works fine for cooking. The ceiling fan makes noise when on inverter, not terrible, but you can tell by the sound when you are on inverter. I have been full timing for 7 years so this is not occasional useage.
 HTH Jim
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DrivingMissLazy
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« Reply #7 on: February 23, 2008, 07:26:07 AM »

Before totally condemning square wave inverters, I think you should become familiar with the PWM (Pulse Width Modulated) inverters/variable speed motor drives. The basic design of these units is actually square waves that are modulated at a higher frequency and then varied to produce the desires output frequency. I have built machines up to 500 HP using them with no adverse effects.

Richard
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« Reply #8 on: February 23, 2008, 07:37:04 AM »

Boogie gets the brass ring! 

But it cost me $500 to learn.    This is exactly what an electronics tech told me after I fried some expensive electronic equipment following the advice of the inverter salesman stating, " 110vac is 110vac - power is power". 

I had a square wave Tripplite. And this was 25 years ago when modified sine or pure sine were few and very expensive. 
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luvrbus
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« Reply #9 on: February 23, 2008, 08:18:14 AM »

Two things I can tell you that don't even like modified sine is a 32in Sony LCD Tv and the Induction cook top fried my new  Sony TV
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jjrbus
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« Reply #10 on: February 23, 2008, 11:07:17 AM »

Maybe we are comparing apples to oranges? The MSW trace DR3624 inverter I'm useing is about $900. Other people I know useing MSW with no problems are useing Freedom, Trace, Xantrax. May be a big difference with the Wallyword/JCWhitney Chinesse units.
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luvrbus
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« Reply #11 on: February 23, 2008, 11:28:01 AM »

JJrbus, I use 2 trace 2012 stacked and they fried my Sony and even using Xantrax you are going to get made in China in some models
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JohnEd
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« Reply #12 on: February 23, 2008, 11:57:17 AM »

I agree with HOBIE.  BOOGIE FOR THE WIN! Shocked Grin Grin

Well said!  Now I got it.  I completely missed the point that we were talking about THREE types of inverters....Square wave, Modified square qave and Pure sine wave.  I am old enuf, they just never reached my event horizon before now.

Boggie,

Never considered the induction (brushless) motor. Embarrassed  I'll bet those are the type found in the AC. Huh

"all the problems you wil never have to solve". Cool  Crimmey!  What wisdom! Roll Eyes  I had my heart set on an "OUTBACK" so you have validated my gut. Smiley

Great communications Boogs.  And from a EE!  Who wouda thunk et?  Your 2 cents might be worth more than $200 even after inflation. Grin

With respect to you (and all others),

John

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« Reply #13 on: February 23, 2008, 12:26:35 PM »

I went with the 3000 watt unit from this guy, and got the inverter, control panel, and auto gen start for just under $1900. Looks like it's gone up about $150 since then.
The RS3000 is an awesome unit.

http://www.donrowe.com/inverters/rs2000.html

Jay
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luvrbus
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« Reply #14 on: February 23, 2008, 12:50:05 PM »

Jay, I heard you couldn't get that inverter till Jun or Jul because of the imported parts backlog from China
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boogiethecat
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« Reply #15 on: February 23, 2008, 01:33:42 PM »

Hey Richard,
You're totally right about square wave AC motor drives, they work really well.

The big difference is, as you mentioned, is "high frequency".

Truth is, even pure sine inverters are square wave inverters at heart. But as opposed to simply making a square wave (or modified one) at 60 hz, pure sine inverters AND the big motor controllers create square waves at very high frequencies, usually 50khz up to sometimes even into the megahertz range, and then those frequencies are pulse width (or similar) modulated so that their energy content is a 60 hz sine wave; the high frequency portion is then filtered out either by LC elements in an inverter or in the case of your big AC motors, by their inherent inductance, and the final result is that the load (motor etc that needs to see a pure sine wave)  actually does see a pure sine wave at 60hz, even though the reality is that the sine wave is actually being created by high frequency square waves.  Make any sense?

Heck, it's all in the smoke.  Keep the stuff inside the wires and anything goes... let it out however it happens, and stuff quits working....
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1962 Crown
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« Reply #16 on: February 23, 2008, 01:39:38 PM »

Jay, I heard you couldn't get that inverter till Jun or Jul because of the imported parts backlog from China


If you need one quick, here's one on the  E place... http://cgi.ebay.com/XANTREX-RS3000-3kw-Sine-Wave-Inverter-Charger_W0QQitemZ250217253616QQihZ015QQcategoryZ41980QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Jay
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luvrbus
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« Reply #17 on: February 23, 2008, 01:47:06 PM »

Jay, my daughter wants one for her S&S and Dan Rowe will have the better price as they have every thing included in the price so she is going to wait till June she said    thanks
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Sean
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« Reply #18 on: February 23, 2008, 02:04:51 PM »

[Comments deleted by author.]

(I misread the post I was commenting on -- my apologies, everyone.)

-Sean
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DrivingMissLazy
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« Reply #19 on: February 23, 2008, 02:09:18 PM »

Hey Richard,
You're totally right about square wave AC motor drives, they work really well.

The big difference is, as you mentioned, is "high frequency".

Truth is, even pure sine inverters are square wave inverters at heart. But as opposed to simply making a square wave (or modified one) at 60 hz, pure sine inverters AND the big motor controllers create square waves at very high frequencies, usually 50khz up to sometimes even into the megahertz range, and then those frequencies are pulse width (or similar) modulated so that their energy content is a 60 hz sine wave; the high frequency portion is then filtered out either by LC elements in an inverter or in the case of your big AC motors, by their inherent inductance, and the final result is that the load (motor etc that needs to see a pure sine wave)  actually does see a pure sine wave at 60hz, even though the reality is that the sine wave is actually being created by high frequency square waves.  Make any sense?

Heck, it's all in the smoke.  Keep the stuff inside the wires and anything goes... let it out however it happens, and stuff quits working....

Thanks for the technical explanation Boogie. 

Some of the equipment I used to manufacture used the three phase PWM motor drives to convert the 300 or 600 volt DC from a battery bank to sine wave AC for computer systems. I utilized a pi type LC filter to remove the harmonics and get a pure 60 hertz sine wave. Just never really knew all the technical details. The fun we used to have. LOL

Richard
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« Reply #20 on: February 23, 2008, 02:22:58 PM »

Sean, I have 2- 2012 stacked and I posted they were modified sine replacing them with 1 new Magnum pure sine when Dick can get it for me
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Sean
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« Reply #21 on: February 23, 2008, 02:29:19 PM »

Sean, I have 2- 2012 stacked and I posted they were modified sine replacing them with 1 new Magnum pure sine when Dick can get it for me


Yes, sorry -- I missed the word "modified" when I read your original post.  I went back and deleted my comments after I realized my mistake.  Not soon enough, I see  Smiley

FWIW, I would definitely not try to run an induction cooktop on anything other than a pure sine unit.  For that matter, I wouldn't run any inductive loads on anything but pure sine.  As Gary said, it's just not worth the worry, or even the performance penalty.

-Sean
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