Inverters; Pure versus Modified Sine Wave

[Sailor Bob 350]

My 1000W Xantrex MSW inverter has

[Sailor Bob 350]

My 1000W Xantrex MSW inverter has worked everything on my boat for years. Handheld radio charger, cordless razor, 900W microwave, electric coffee maker. The only two oddities are my older LCD TV wouldn't work unless you unplug it, turn on the inverter, then plug it in. My new Samsung doesn't care. And my 120V iPhone charger won't work at all; but I don't need it, since a car charger at 12V works just fine.

[mitiempo]

Originally Posted by Sailor Bob 350

My 1000W Xantrex MSW inverter has worked everything on my boat for years. Handheld radio charger, cordless razor, 900W microwave, electric coffee maker. The only two oddities are my older LCD TV wouldn't work unless you unplug it, turn on the inverter, then plug it in. My new Samsung doesn't care. And my 120V iPhone charger won't work at all; but I don't need it, since a car charger at 12V works just fine.

Surprising that a 900 watt (cooking power I assume) microwave will work well with a 1000 watt MSW inverter. The cooking power of a microwave has little to do with its power consumption. All microwaves consume a lot more AC power than their rated cooking power. My 700 watt microwave consumes over 1100 watts on high.

[Sailor Bob 350]

Real life sometimes trumps theory. Perhaps the inverter output exceeds what it's rated.
I never used the microwave for more than 2 min - the power drain is awful!

[transmitterdan]

Originally Posted by Sailor Bob 350

Real life sometimes trumps theory. Perhaps the inverter output exceeds what it's rated.
I never used the microwave for more than 2 min - the power drain is awful!

Theory explains what happens in real life. In this case theory demands that a MSW must produce less peak voltage and thus less power into the magnetron. Therefore the microwave is not making anywhere near 900W when running on the inverter. It's a very common issue. Some people don't use the microwave enough to really care which is fine.

[Sailor Bob 350]

Heated my coffee up, I considered it a complete success!

[Maine Sail]

Originally Posted by mitiempo

Surprising that a 900 watt (cooking power I assume) microwave will work well with a 1000 watt MSW inverter. The cooking power of a microwave has little to do with its power consumption. All microwaves consume a lot more AC power than their rated cooking power. My 700 watt microwave consumes over 1100 watts on high.

Not all that surprising on MSW because the load will be less than it is on pure sine or shore power..

On the 1000W "rated" microwave I nmentioned above I threw my Kilowatt meter on it and and ran it off both shore and his inverter. It drew 1510W +/- on shore and only 990W +/- on his old Freedom MSW inverter. It is entirely possible the microwave is drawing less than its face value 900W rating while running of an MSW inverter, depending upon how bad the wave is...

I know my 700W microwave draws 1190W at 119V on shore power. If I plug it into an MSW it draws considerably less....

[rwidman]

Rather than join in the arguments on theory vs actual experience and leaving out the part about building one's own inverter, here are my experiences:

My laptop and phone chargers work fine on a modified sine wave inverter. So does my coffee maker. I have run power tools on it and they work just fine.

On my previous boat, the microwave worked fine on a modified sine wave inverter. On my current boat, the original microwave was unreliable on a modified sine wave inverter. It would often have to be started multiple times before it would begin actually cooking. You could tell by the sound if it was cooking or not.

I replaced the microwave with one I knew I could return if it didn't work on the inverter. It does work on the modified sine wave inverter but it is louder and by actual testing (by me) cooks slightly slower on inverter power. About 10% slower and to me that is acceptable.

Life would be easier with a sine wave inverter, the question is, is it worth the difference in cost?

[valhalla360]

Originally Posted by nimblemotors

Isn't it about time for someone to say how things not designed for a marine environment will not last in a marine environment..

Sounds like someone would be a customer for a lower power, more efficient 12v microwave. The ones I have taken apart use solid wires from the transformer to the capacitor. These are fine in a house, but can work harden and break in a marine environment.

When you can buy a new microwave for $30 it's tough to justify a $500 marine grade 12V microwave.

Our $30 cheapo is going on 7yrs old with no issues (haven't bothered trying to use in with the inverter though)

[rwidman]

Originally Posted by mitiempo

........... The cooking power of a microwave has little to do with its power consumption. All microwaves consume a lot more AC power than their rated cooking power. My 700 watt microwave consumes over 1100 watts on high.

It has something to do with power consumption. The higher the cooking power, the higher consumption.

The actual power consumption (not cooking power) will be on a label, usually on the back near where the power cord is attached. This is what you need to know when selecting an inverter.

[rwidman]

Originally Posted by nimblemotors

............ Now I'm working on converting the microwave to be lower power and run on 12v. Was going to start on a thread on this, I would think such a unit would be marketable, they don't seem to be available, only one company makes a small one.

A 12 volt microwave would be nothing more than a 120 volt microwave with a dedicated inverter. Using a separate inverter and microwave allows the inverter to be used for other purposes. It also allows for the economy of using mass produced and sold microwaves and inverters.

[smac999]

Who would buy a non sine wave inverter in the year 2014? This isn't the 80's anymore. There is no need for decussion.... Really there isn't. I don't even know why they still make square ones.

[rwidman]

Originally Posted by smac999

Who would buy a non sine wave inverter in the year 2014? This isn't the 80's anymore. There is no need for decussion.... Really there isn't. I don't even know why they still make square ones.

Tell us how you really feel.

[nimblemotors]

A sine wave inverter is more complicated and less efficient having to simulate a rotating magnet.

Using an inverter at all is more complicated and less efficient.

Some people don't care much about efficiency, some people do quite a lot.

[bobofthenorth]

Seems to me there's a lot of dickie waving and chest thumping going on in this thread so I'll just quietly state our single data point:


10+ years of using 2 Heart Freedom 25 MSW inverters. Everything we have hooked up to them has worked just fine - computer bricks as well as innumerable other electronics bricks and wall warts, flat screen and antique TVs, printers, scanners, microwaves, convection ovens, fridges, freezers, large number of power tools and battery chargers for power tools - if it consumes 110V we have plugged it in and it has worked. Within that universe of "things that work", perhaps the microwave on the boat has worked less ideally than it does on shore power but that may also be my imagination. I've had various people tell me that various appliances either wouldn't work or, if they did work, they would soon fail. So far their predictions have been uniformly wrong. But then again, I plan to live forever and so far that plan is working as well.