MSW versus PSW Inverters...

[MikeRuth]

Thought I'd post this just to let newcomers know what I experienced using a MSW(modified sine wave) inverter. 
PSW (which is Pure sine wave) provides a power that is much closer if not as good as your wall outlet from standard utility service. 

I recently took a cross country trip and just before I left I put in a Microwave oven. I have a HF 2000 Watt MSW inverter running off two Trpjan T-105 batteries in series. 

Now the batteries and inverter have absolutely no problem powering up the MW, but what I did experience is the loss of power due to the MSW. 

The MW will as an example cook up a frozen breakfast bowl in 3 minutes on shore power. Just as it should. But with it running on the MSW inverter the time to cook the same increased about 60%! Now the MW powers up, light comes on and the platter spins just fine, it's just the power from the actual MW system is less. I used it multiple times with no issue other than the increased cooking time, which in a way is a problem as your pulling on your batteries say 60% percent longer. 

Knowing it wouldn't really make a difference I did just for kicks try the same with the alternator added into the system, all that really did was just support the batteries and maintain a slightly higher operating voltage, but cook time was still increased, and I expected that. 

So for me I'll be looking into a PSW inverter soon as I'd really prefer to get the most out of my batteries. 

speaking of batteries and I could be considered a newbe as I installed them just 4 years ago, these T-105's are still going very strong. 
I use 240 Watts of Solar through a TriStar TS-45 Controller and support that with switchable Alternator power when needed. 

I'm not sure how much better my system would run on a MPPT controller as my needs seem to be met quite well with this setup. 

Hope this helps someone!

Mike R

 

[Elbear1]

It also takes less power out of your batteries. Its a zero sum. TV, Computers, induction cooktops, toaster ovens, all fine on MSW. fans, fridges, microwaves run harder and longer but still work.

PSW has a much higher idle current due to the components used to smooth the wave. Theyre also much larger. Overall MSW most efficient, compact, and if youre running 12v fan and fridge like most do theres no good reason to bother with PSW.

 

[tx2sturgis]

This aligns with my experience with modified sine inverters powering a microwave....it takes longer, the oven runs hotter, and buzzes or hums noticeably louder than on sine wave or shore power AC.

In other words, efficiency drops off.

 

[Trebor English]

Does anybody have a similar result with a Honda Eu2000 or Eu2200 or some other gasoline powered device? Has anybody measured the 120 volt AC power while the microwave is slow? Does anyone have a microwave that is sufficiently low powered to be able to use a Kill A Watt?

 

[highdesertranger]

I don't use a micro wave but I can tell you my MIG welder and Plasma cutter work fine off of my Honda EU2200i. the Plasma cutter in particular is real sensitive to having a clean stable voltage source. highdesertranger

 

[wayne49]

My finding is to either buy a cheaper inverter with twice the watts that you need or spend twice as much for a quality unit.

Another point is to think how critical is the load to your daily living. If it is powering a refrigerator with food and/or medicine, you might want to think about purchasing a backup inverter.

Batteries degrade slowly, unless shorted by something that won't melt easily.
Inverters work or they don't work.

 

[B and C]

I have a microwave/convection oven and run it off my Onan microlite 2800 watt generator. The microwave and oven work the way they should, no unnatural noises or longer cook times. I press the popcorn button and the popcorn gets done. The oven has no problem reaching set temperature.

 

[Ticklebellly]

Now the batteries and inverter have absolutely no problem powering up the MW, but what I did experience is the loss of power due to the MSW. 

So for me I'll be looking into a PSW inverter soon as I'd really prefer to get the most out of my batteries. 

Your apparent loss of performance described as a loss of power is easily explained by looking at the wave shape of the inverter output.   MSW inverters do not output a modified sine wave.   Rather they output a stepped square wave.   The number of steps and the voltage level changes more or less vaguely approximates a sine wave shape.    Each cycle of the output also includes a change of polarity so that the output is Alternating and therefore the energy can be transformed through transformer methods.   A meter on the output of an inverter reports the RMS (Root Mean Square) value of the peak voltage of the waveform of the output being measured.    A RMS number of a proper sine wave is a standard understanding of the energy contained in the waveform.   A stepped waveform like from a Modified SQUARE wave inverter is does not provide a standard measure of the energy contained in the waveform.   It is always less than the reading would suggest.

A PSW inverter will not let let you get more out of your batteries.   As an earlier post says, it is a zero sum situation.   The energy in the output is directly proportional to the what is drawn from the battery.   Yes, a Modified Square Wave inverter will run a MW but with reduced efficiency.   The reduced efficiency can be seen in the device running hotter and emitting more noise.

As a general rule, computers and the like are OK with the stepped output as their power supply front ends only require Alternating polarity and a rise and fall somewhat like a sine wave.    Electric motors on the other hand get quite upset trying to run on anything less than a proper sine wave.

 

[66788]

Honda invertor/generators are pure sine wave.