Modified Sine Inverter Uses

[DPC]

Unscientific, but my hefty APC 3000XL (2700W LF) UPS can start my 1/2hp garbage disposal without blinking. My lightweight 2500W HF Reliable can barely start the disposal, and will brown out the entire house making other items turn off.

My little APC 750 VA starts my 1/3 hp sump pump too.
Its also a cheap modified sign wave.
No complaints does as its asked, low inertia load.

 

[Supervstech]

Back in the early 2000’s I had a 2000W MSW inverter tied to a massive car battery bank.
It ran all my cfl lights, and my gas furnace without difficulty…

 

[DPC]

Just an observation about Furnaces.
They seem to have the worst electronics in them.

I am real suspect of Any boards in whirlpool products to be specific

The simpler and dumber something is the more likely it is to last.
The trade off seems to be lower efficiency in most cases.

The highest efficiency furnace will probably have the best return on investment than say a gravity furnace.
But that old Gravity furnace will likely never ever fail......

 

[Supervstech]

Just an observation about Furnaces.
They seem to have the worst electronics in them.

I am real suspect of Any boards in whirlpool products to be specific

The simpler and dumber something is the more likely it is to last.
The trade off seems to be lower efficiency in most cases.

The highest efficiency furnace will probably have the best return on investment than say a gravity furnace.
But that old Gravity furnace will likely never ever fail......

And it won’t need ANY electricity to operate… unless it is oil burner… but I’ve worked on a slew of gravity oil wick furnaces… foot burners they should be called… gotta wear shoes when walking over them!

 

[DPC]

Half your money goes up the chimney

I have one of these at camp from the 1940s.


Its a back up to an equally inefficient wood burning furnace

I do not advocate anything like this for heating.
I'm just making a point they seldom fail to function.
I am not sure they are even a safe consideration

 

[zanydroid]

I’d love to watch some clickbait on the top ten 80%+ efficient appliances with no electronics control boards, actuators, power conversion inside.

I can only think of a toaster and resistive hot plate.

Nothing in the combustion space

Can a condensing heat exchanger be designed without electronics or pumps?

 

[JayArr]

The PSUs just rectify, and don’t care about the waveform.

That's an important fact. Modern electronics power supplies use a three stage process to make the low voltage DC required by the TV/computer. The first stage is just a bridge rectifier. In order to save money all power supplies are now built to work anywhere in the world so this first input section will take in up to 240VAC and rectify it to about 320-340VDC. In North America it takes 120VAC and makes it 160VDC.

This first section does not care if the input waveform is pure sine or modified, it's a simple set of four diodes that don't care what the rate of change is. In fact you could feed 320VDC directly into the power supply and it would simply pass it through the bridge and other than over working two diodes and not working the other two it would be fine.

The second stage is what's called power factor correction. This section takes the raw DC from the first stage and boots it up to about 385VDC but it's more important function is to keep the power draw from the grid in phase. When you start things with magnetics (electric motors) you go out of phase in one direction and when you start things with capacitors (computer power supplies) you go out of phase in the other direction. When you start something with a resistive load (electric heater) you stay in phase. Drawing out of phase is a big headache for the power company so we've evolved to keep out gear as close to phase as possible.

The last stage is referred to as the DC-DC stage. It takes the 385VDC and bucks it down to whatever is needed by the device. Computers commonly use 3.3V, 5V, and 12V. TVs also commonly use 48V for the lights. All of these output voltages are derived from the 385VDC.

So... with three highly regulated circuits between the power source and the IC the power would have to be incredibly dirty to affect it. Modified square wave alone is not going to penetrate this level of circuitry.

Years ago when there were no power factor correction circuits between the bridge and the DC-DC supply (remember when there was a 120/240 switch on the back of things?) it was more sensitive and susceptible to bad power and I think some people think it's still like that.

I repair inverters for a living and a lot of them are the Xantrex MSW. They work just fine in most RVs boats and tractor trailer cabs and the electronics don't have any problem with the MSW. I have one in my trailer and it runs my microwave, laptops and TV and there is no problem, they are not inherently bad or inferior.

You do have to be aware that there is a difference between MSW and dirty power.

You can believe that MSW is bad for "sensitive electronics" if you like, it's a free country. Marketing departments relay on this to sell stuff to people who relay on sales literature to get the facts on things they want to buy. Caveat Emptor.


JayArr

 

[JayArr]

efficient appliances with no electronics

My mind goes to my trailer and it's gas appliances...

Ammonia refrigerators - think RVs - nothing but a small pilot flame and a mechanical thermostat.

Hot water tanks - flame and mechanical thermostat.

Gas stove.

 

[zanydroid]

Last time I tried to use that MSW, I plugged it into a LCD monitor with integrated AC power supply.

It started buzzing out all the extra harmonics so loudly that it was not comfortable to sit in front of and made me worry about its health

Are active power electronics that lock onto the fundamental AC/pulsed DC frequency smart enough to handle the harmonics? Active power correction and ideal diodes come to mind. The latter likely does not care if it only locks to the crossings.

 

[seneysolar]

I repair inverters for a living and a lot of them are the Xantrex MSW. They work just fine in most RVs boats and tractor trailer cabs and the electronics don't have any problem with the MSW. I have one in my trailer and it runs my microwave, laptops and TV and there is no problem, they are not inherently bad or inferior.

You do have to be aware that there is a difference between MSW and dirty power.

You can believe that MSW is bad for "sensitive electronics" if you like, it's a free country. Marketing departments relay on this to sell stuff to people who relay on sales literature to get the facts on things they want to buy. Caveat Emptor.

Thank you for this. I was thinking along these lines. Seems the marketing of pure sine products has associated MSW with dirty power to the point where people are afraid of it no matter what application.

I have a few MSW inverters, one in my truck, another on a portable battery pack. I have never noticed anything different and i dont discriminate what i plug into it. Then i started looking at inverter generators and realized most are MSW anyways and nobody else notices either... but when folks buy inverters for solar its pure sine or nothing.

 

[DPC]

There is another thread here where the conversation was on off grid washing machines.
In that thread I proposed a counter flow heat exchange to recover heat from a drier to reduce its heating requirement.
I think its 50% achievable recovery thats huge.
Years ago I made my own beer and I used counter flow heat exchanges to strip the heat out of parts of the process to crash cool things and rapidly warm things.
Now I think about it all the time

Same things can be done with a lot of heating systems the problem is without external power as your flue gasses are cooled by heat recovery your draft goes for a poop.
You need an energy input to run fans, but you don;t need a lot of electronics to do it, its just cheaper that way to manufactures.

If going down another off topic wabbit hole someone want to start another thread?
I'm always thinking about this stuff because its such a hassle to carry in fuel for camp.

I'm thinking about wood as a fuel source, direct solar heating and power generation, lake water cooling....
I'm thinking all the time but so far built nothing.
For a decade I gave this a lot of thought...

I joined this forum so I could learn from some experts on the best use of solar power generation but I'm always interested in any other Solar idea.
To me Biomass is Solar energy in another form..

 

[zanydroid]

Thank you for this. I was thinking along these lines. Seems the marketing of pure sine products has associated MSW with dirty power to the point where people are afraid of it no matter what application.

I have a few MSW inverters, one in my truck, another on a portable battery pack. I have never noticed anything different and i dont discriminate what i plug into it. Then i started looking at inverter generators and realized most are MSW anyways and nobody else notices either... but when folks buy inverters for solar its pure sine or nothing.

It’s also possible a lot of the noise is from salty people like me that bought an MSW inverter on a whim for unspecified appliances, and out of the first 10 appliances plugged in 3 were extremely unhappy.

Contrast that with my PSW inverter generator that I bought at the same time. Much much much happier with that and have FOMO for not also owning a PSW battery inverter instead of only the MSW battery inverter. IOW if I only can ever own one, PSW would be better.

If you have an understanding of the pros and cons and the space to have specific inverter types for each application then MSW can have its place.

 

[JayArr]

It's also possible that the MSW inverters that have given people problems were cheap Chinese trash and now all MSW inverters are getting tarred with the same brush.

The trouble may not be the MSW it may be the cheap Chinese design and manufacturing.

I owned a brown Ford Pinto hatchback once and it was a real shitbox. That doesn't mean all brown cars or all hatchbacks are shitboxes. It doesn't even mean all Fords are shitboxes.

We need to be careful how we judge and where we lay blame.

 

[DPC]

It's also possible that the MSW inverters that have given people problems were cheap Chinese trash and now all MSW inverters are getting tarred with the same brush.

Well....
Going back many years the first generations of industrial electronics gave everyone a lot of trouble
Slow switching speeds and really ugly wave forms made some motors run hot.
Under some special conditions of long runs of cable and large motors and drives you could get reflect waves causing voltage spikes that were killing motor insulation and burning the ends of the cable insulation.

These were the neanderthals of drives...

You know I cant even find pictures on google of the stuff I am talking about.
I have a board from a very early SILPAC in my locker at work.
Its so old, so early, the traces on the electronic boards were drawn and etched by hand probably in the 60s...
( dawn of the transistor age )

I am old enough to have worked on stuff with tubes in it.
Man things change fast.

This is the big guy from Creighton #9
It I think still is the deepest single rope skip hoist in the western Hemisphere
What you cant see are the twin Silpac drives from the 1960s that run it.
You can hear the hum and harmonic noises it makes...
It produced so much objectionable noise from harmonics on the AC power system and ground currents that when that motor turned I was scared to disconnect a ground in the building from unrelated equipment that just happened to be close to it because it might draw an arc.

Rest in peace Big guy....

Here's the grand old lady of electric truck fleet 910
Listen real good...
You can hear the howl of the ABB thyristor converter of another truck behind her running up to full power to do a brake test before they rolled off to do a days work.

Video taken on a 2 Megapixel Kodak digital camera....

 

[Lt.Dan]

My parents have a MSW inverter in their Monaco Diplomat motorhome (a very nice Magnum model), and they have burnt out more coffee makers than I can count on both hands! Let alone other equipment that has friend from it.

I have tried telling him for the last 7 or 8 years, to replace it with a PSW model, and that with replacing all this equipment, a nice Victron inverter would have been cheaper! He finally has agreed, and in 2 weeks, we are putting in a Victron MultiPlus 3kVa!

 

[DPC]

Maybe its the water....

 

[seneysolar]

My parents have a MSW inverter in their Monaco Diplomat motorhome (a very nice Magnum model), and they have burnt out more coffee makers than I can count on both hands! Let alone other equipment that has friend from it.

I have tried telling him for the last 7 or 8 years, to replace it with a PSW model, and that with replacing all this equipment, a nice Victron inverter would have been cheaper! He finally has agreed, and in 2 weeks, we are putting in a Victron MultiPlus 3kVa!

Someone on here said coffee makers dont care. Resistive heating? Maybe the fancy ones that auto brew are sensitive?

The $25 cheap ones with just a rocker switch seem to be the best.

 

[zanydroid]

Coffee makers are one of those appliances with all sorts of crazy AC / DC input hacks.

10-15 years ago (and maybe even today) there were people stacking dimmers, variacs, what have you and PID controls in front of their cheap resistive coffeemakers to tighten up the temperature control.

 

[zanydroid]

Would plugging an intelligent robot with motor windings in it, or a historically significant vintage equipment, into a MSW inverter count as a hate crime / crime against humanity?

 

[12VoltInstalls]

A gfci shouldnt pop due to pure sinewave vs mod sine wave. The pop due to differential in the 120v leg vs the neutral or ground.

I’ve wondered about adding some capacitors but I’m unclear if that will thwart GFCI function and I sorta like the GFCI functioning.

I made no reference to MSW tripping GFCI
I just said it happens and wondered if adding capacitors would keep the uneven voltage from occurring, and if that would affect GFCI function