Modified or Pure sine wave inverter?

[unioncreek]

I have noticed that the pure sine wave inverters cost quite a bit more than the modified. I'm putting together a system to run my pellet stove and a 12 volt pump for my water supply. Is it worth the expense to go with a pure sine wave over the modified.

Bob

 

[Supervstech]

Yes.

Motors, and electronics perform far better on pure sine wave output.

 

[E. Cho]

Yes.

Motors, and electronics perform far better on pure sine wave output.

Too simplistic and general a statement in my experience. I had a Trace modified sine wave inverter for years and it ran everything I tried, motors to computers. I was scared by the talk of pure sine wave being superior for electronics, so switched to a Trace SW4024 Pure sine Wave inverter, but I noticed zero difference with the same appliances, motors, etc.. Now long term in years, or per appliance, they may last longer with pure sine wave power?

And, recently bought a lower cost 3000 Watt pure sine wave inverter for a friend and it would not run some motors and failed with a 10 amp vacuum cleaner. It was an HF or high frequency inverter, so I then had to go and find a lowish cost, used, Aims Low Frequency inverter to run the vacuum etc..

Plus it depends on the battery and wiring capacity.

Point being, in my experience, it depends on the inverter and appliance (load), plus wire size or length, plus surge if required.

Inverter manufacturers are very poor and elusive on information on exactly what motors will or won't run vs. very general.

I'd advise asking manufacturers for specifics and or specific user reviews or for the exact application and invertt you are talking about.

 

[Supervstech]

Too simplistic and general a statement in my experience. I had a Trace modified sine wave inverter for years and it ran everything I tried, motors to computers. I was scared by the talk of pure sine wave being superior for electronics, so switched to a Trace SW4024 Pure sine Wave inverter, but I noticed zero difference with the same appliances, motors, etc.. Now long term in years, or per appliance, they may last longer with pure sine wave power?

And, recently bought a lower cost 3000 Watt pure sine wave inverter for a friend and it would not run some motors and failed with a 10 amp vacuum cleaner. It was an HF or high frequency inverter, so I then had to go and find a lowish cost, used, Aims Low Frequency inverter to run the vacuum etc..

Plus it depends on the battery and wiring capacity.

Point being, in my experience, it depends on the inverter and appliance (load), plus wire size or length, plus surge if required.

Inverter manufacturers are very poor and elusive on information on exactly what motors will or won't run vs. very general.

I'd advise asking manufacturers for specifics and or specific user reviews or for the exact application and invertt you are talking about.

Oh indeed, hf inverters have little to no surge cushion for motor loads, so the running watts needs to be far higher to start a motor load, but that isn't what we are discussing here... the question is "is pure sine worth the difference in cost over modified sine"
And I would stand by my statement that a low cost msw is worth less for some loads, motor and electronics specifically.

Sure, a high quality msw inverter likely won't be nearly as detrimental as a low cost one would be.

Ya rolls yer dice and takes yer chances...

 

[rin67630]

Too simplistic and general a statement in my experience.

Yes, definitely.
Motors are not all the same.
Universal brushed motors (e.g. a drill) will run fine on modified sine inverters, excepted those controlled by a phase shift triac as a speed control.
Asynchrounous motors will perform poorly and potentially overheat since the second phase is achieved with a capacitor that should shift a real sinus by 90°, but they will not shift a square signal.
Most electronics incl. computers will run perfectly fine on modified sine since their input power supply circuit is a rectifier anyway.

 

[pollenface]

My pedestal fans don't like MSW. They run but make alot of buzzing.

I have a 110w msw in my vehicle which I've had for years. As above, anything with a switching power supply is fine.

 

[petee_c]

we had a couple blackouts this weekend. I got a 400w modified sine wave inverter to run with my 50Ah 12v LifeP04 battery. ran my worklaptop, monitor, and internet router on it for a couple hours until it was late enough that we didn't feel bad firing up the gas generator.

seemed to work fine. I tested it with my Cpap machine and it ran it fine too...

I'm in the return window for it still, and may send it back and get a pure sine one...

Our refrigerators ran fine on our modified sine wave gas generator as well....

 

[rin67630]

And I would stand by my statement that a low cost msw is worth less for some loads, motor and electronics specifically.

I agree for some motors. Regarding electronics it heavily depends.
90% of the current electronics have a switched power supply upfront that will first rectify AC to DC so the waveform does absolutely not matter.
A few devices like "smart lamps, radio controlled plugs, programmable coffee makers use a direct power supply where the excess voltage is reduced by a capacitor. These devices will very likely burn through, since the capacitor will not work on square waves like it should and pass the full voltage as surges.
Old white appliances with asynchronous motors will perform badly since they us a capacitor to make the 2nd phase from AC and that one will not work too.
New washing machines have an electronically controlled motor and do nor rely on the AC waveform.
A drill and most hand tools work with an universal motor are fine with MSW at full power.
An eventual phase split-speed controller will probably not work at all and just deliver full power.

 

[rin67630]

My pedestal fans don't like MSW. They run but make a lot of buzzing.

Normal: they use an asynchronous motor that gets its 2nd phase from a capacitor.

 

[petee_c]

I agree for some motors. Regarding electronics it heavily depends.
90% of the current electronics have a switched power supply upfront that will first rectify AC to DC so the waveform does absolutely not matter.
A few devices like "smart lamps, radio controlled plugs, programmable coffee makers use a direct power supply where the excess voltage is reduced by a capacitor. These devices will very likely burn through, since the capacitor will not work on square waves like it should and pass the full voltage as surges.
Old white appliances with asynchronous motors will perform badly since they us a capacitor to make the 2nd phase from AC and that one will not work too.
New washing machines have an electronically controlled motor and do nor rely on the AC waveform.
A drill and most hand tools work with an universal motor are fine with MSW at full power.
An eventual phase split-speed controller will probably not work at all and just deliver full power.

Any idea on a modern furnace and MSW vs pure?

 

[time2roll]

we had a couple blackouts this weekend. I got a 400w modified sine wave inverter to run with my 50Ah 12v LifeP04 battery. ran my worklaptop, monitor, and internet router on it for a couple hours until it was late enough that we didn't feel bad firing up the gas generator.

seemed to work fine. I tested it with my Cpap machine and it ran it fine too...

I'm in the return window for it still, and may send it back and get a pure sine one...

Our refrigerators ran fine on our modified sine wave gas generator as well....

Most power supplies don't care about PSW. Although I have found some will run a bit hotter. If the device basically runs on DC it is not an issue.

Standard generator creates a natural sine wave same as a utility scale generator. If the wave becomes deformed it is mostly from the interaction with the load.

 

[Supervstech]

Most power supplies don't care about PSW. Although I have found some will run a bit hotter. If the device basically runs on DC it is not an issue.

Standard generator creates a natural sine wave same as a utility scale generator. If the wave becomes deformed it is mostly from the interaction with the load.

Yup, standard generator has no choice but to output. Pure sine wave.
The issue with them is the frequency shifting all over the place from the RPM changes under load.

 

[rin67630]

Any idea on a modern furnace and MSW vs pure?

It depends on which motor it uses.
A motorless gas furnace will probably run well.
Asynchronous motors will not run well.
For a few hours backup on power outages, MSW may be acceptable.

 

[time2roll]

I recommend sine wave for any motor.

 

[Supervstech]

I recommend sine wave for any motor.

Modern furnaces use ECM motors, either variable speed, or constant torque.
They all have dc inversion to power the motor. How would that fare with MSW vs. PSW? Several large capacitors in the circuitry.

 

[rin67630]

Modern furnaces use ECM motors, either variable speed, or constant torque.
They all have dc inversion to power the motor. How would that fare with MSW vs. PSW? Several large capacitors in the circuitry.

If they have en ECM motor, or variable speed motors, they should work fine with MSW, everything that is rectified upfront works fine.
But sometimes you als have circulation pumps with asynchron motors, there is an issue too.

 

[rin67630]

I recommend sine wave for any motor.

Pearls to pigs, frequently.

 

[Moltensurf]

Yes, definitely.
Motors are not all the same.
Universal brushed motors (e.g. a drill) will run fine on modified sine inverters, excepted those controlled by a phase shift triac as a speed control.
Asynchrounous motors will perform poorly and potentially overheat since the second phase is achieved with a capacitor that should shift a real sinus by 90°, but they will not shift a square signal.
Most electronics incl. computers will run perfectly fine on modified sine since their input power supply circuit is a rectifier anyway.

Do you think a modified sine wave will run a mini fridge? I have an mppt lv2424 but I would like to get a smaller inverter dedicated to the refrigerator and wire it to the thermostat so there is not a constant power drain on my batteries.

 

[rin67630]

Do you think a modified sine wave will run a mini fridge? I have an mppt lv2424 but I would like to get a smaller inverter dedicated to the refrigerator and wire it to the thermostat so there is not a constant power drain on my batteries.

Probably not well. Fridges are almost always driven by asynchronous motors, with a capacitor to give a rotating field. This one deals not well with MSW.

 

[rin67630]

Any idea on a modern furnace and MSW vs pure?

It all depends on how the electronics are supplied: with a copping power supply or with a capacitor direct power supply.
Regarding the power circuit it should not matter a lot.