Microwave and Inverter don't play together well

[S/V Alchemy]

Originally Posted by gbr

You have been misled. I run ours using our Victron Inverters all the time.

OP: You will almost certainly need a pure sine wave inverter for any microwave. Also, some coffee makers need pure sine wave as well. A lot of things with electric motors (depending on type) - need pure sine wave.

Might be an expensive proposition to replace your current inverter, but that is what I would do if you want a Microwave and not start your genny.

I can't speak to the sine wave profile of the OP's inverter, but both my Xantrex RS 2000 (which ceased to communicate with its SCP and became useless) and my much better Victron MultiPlus 3000 Kva were both able to run my old Sanyo 1500W microwave without an issue. Also my ShopVac, my computers and my display screens, without interference lines that are a sign of sine wave mismatch.

[Frankly]

Have played this modified sine wave inverter/ microwave oven business for over 20 years. The earlier microwaves usually would operate but at a reduced output and made a little more noise. As time has moved fwd the microwaves that will tolerate the MSW are getting fewer and fewer. Mechanical timers would appear to be of the more tolerant variety. Finally gave up on my Freedom inverter chargers and bought a pure sine wave. Everybody plays nice. I am 3 months into a Renogy 1000 watt PSW and so far so good ( cost less than $400).

[sasirles]

Stu Jackson: "Could you please explain inverters charging batteries? That one got right by me...."

Inverters charging batteries reminds me of the ice skate boat in Barbarella that ran a fan on the stern to power the sails.

[stormalong]

Originally Posted by Jdege

Most electronic devices use DC internally. They run AC through a transformer, then a rectifier, then a voltage regulator, to get a clean DC input.

Which is why it always odd, to me, to run then off an inverter.

Are microwaves different? Does the magnetron require AC?

A magnetron is a high voltage device. It is supplied high voltage power via a transformer. A transformer is an alternating current device. With the high cost of copper appliance manufacturers are making the transformers as cheaply as possible. They are designed to the minimum standard and can't handle any variation from the normal, grid supplied power.


An inverter draws ten times the amperage from the battery that it delivers to the load. A 1500 watt load means a 150 amp draw on your batteries. Is your wiring up to this load? Are you having a brown out from overloading the DC side of the inverter?

[roverhi]

There are microwaves and then there are microwaves. Most are all electronic controls with nifty digital displays. Then there are basic ones with a twist mechanical timer and virtually nothing electronic other than the magnetron. Will these simpler microwaves work where the newer totally electronic ones won't??? Can't remember what Xantrex flavor the inverter is but doubt it is a full sine wave as it wasn't all that expensive.

Years ago when we were living off the grid, the inverter kept blowing up the controls on a Sears gas oven. After three warranty repairs they gave us our money back. The gas cooktop and all other appliances worked fine. On the boat's inverter, couldn't get a professional quality Bosch sabre saw to work. It's a variable speed tool and assume the speed control is electronic. It works fine on the grid power and didn't suffer from trying to run it off the inverter. A cheap sabre saw from Home Depot works fine.

[Valmika]

An inverter draws ten times the amperage from the battery that it delivers to the load. A 1500 watt load means a 150 amp draw on your batteries. Is your wiring up to this load? Are you having a brown out from overloading the DC side of the inverter?[/QUOTE]




I have a similar problem. I have a really nice Magnum 2k Inverter charger. It is a Modified wave though. I just wired it in were my old 30 amp smart charger was (and did not change the wires to the battery bank) I was told that my wires from the charger to the bat bank although probably enough to handle charging the batteries, may not be large enough to draw a high load from the batteries in inverter mode trying to run the Microwave. I still am not sure because I haven't run bigger wires yet but am very interested in this thread.

[a64pilot]

You need to mount it as close to the bank as you can, a couple of feet if possible, then run stupid big cables.
My MS 2812 requires 4/0 wire and max run is 10 ft, less is better.

[sainted]

I have a Freedom 20 Inverter/Charger, which puts out modified sign wave. My 1000W Sharp microwave works with it, but it makes a louder humming noise. My Yamaha receiver, blue ray player and Insignia LED TV all work great on inverter power. No noise whatsoever.

I'm actually dreading the day when my inverter conks out. I have the Freedom Link 2000R battery monitor, which includes my alternator regulator, hooked to it. Its a great system. When the inverter goes, I'll have to replace it all (since late model Xantec inverters aren't compatible with it). Ack!

I probably won't go with Xantec, though. Magnum and Victron seem like better products these days.

[michaelratinter]

Our old 1500 watt Heart inverter powers an old microwave just fine. Battery charging circuitry inside the inverter chassis charges batteries when the inverter is connected to shore power.

[billgewater]

Although I could not find any internet references, I had heard that MW ovens besides being possibly very dangerous if the radiation is not "sealed" are not just sensitive to the AC power supply wave form but that they are also sensitive to the supplied power RMS voltage and the frequency. US users use 60 Hz but others use 50 Hz. Apparently it affects the magnetron. If (and I stress "if") this is true then to rely on any inverter or even a gen. set is pushing your luck a bit. Also the waveform/voltage and frequency of the inverter supplied out-put may wobble when high loads are applied. Different models may have different "protection" circuitry - or none.

I think this is why we have a range of responses because it is a bit of a lucky draw.

I understand that you can purchase MW ovens that actually use 12 VDC input with associated frightening current requirements (and much higher purchase pricing). However they are probably more efficient than battery to inverter to MW systems. Apparently the trick is that the MW ovens are only used for short periods of time.

Anything can die in a MW oven but a common culprit is the very large electrolytic capacitor. It is very easy to identify and replace this component. (Having saved a couple of more expensive convection models over the years.) Anything else usually means replacing the entire unit.
The only place where I have seen MW ovens being repaired was in the back streets of New Delhi. Not sure why though.
My dad said that all electrical devices have smoke put into them in the factory and when the smoke comes out, they won't work any more. Certainly applies to MW ovens.

[Wayfarer1008]

I'm not talking about house batteries but things like phone and other rechargeable devises.

[dkenny64]

most microwaves can and will run from the newer modified sinewaves.
done it for years..from 2004 until 2011 I used a microwave powered by an inverter in my work bus. while they don't work as well compared to AC power..as in longer heating times..they do work. they'll make more noise..
your not feeding the hi voltage transformer with 60HZ sine..

the clock might not keep the correct time..SO?


FYI some power tools..those with a soft start.. these DON'T LIKE modified sinewave...my Makita chopsaw doesn't like a modified sine...so I have 1:1 transformer on the output to the chopsaw..


-dkenny

[transmitterdan]

Wow, so much speculation/misinformation in this thread...

A microwave uses a magnetron which needs two thousand volts DC (more or less) to make the RF. It is an oscillator so to work right it needs the right voltage. Typically the DC supply of cheap microwave ovens is not a fancy regulated supply. If the DC voltage is too low the magnetron won’t oscillate at the right frequency and the tube will overheat (DC going in but no RF going out).

The rectifiers in the oven output a voltage proportional to the peak of the AC input. Modified sine wave inverters output a lower peak voltage but the normal RMS voltage. Thus most microwaves end up overheating on modified sine wave inverters and they produce lower power.

A generator should produce the right waveform as should a true sine wave inverter.

There are some high end microwaves with regulated DC power supplies. These will work on a modified sine wave inverter. But such microwave ovens are not cheap thus not found on many boats.

If you smell something funny turn it off before you kill the magnetron. Then get a true sine wave inverter rated for 2-3 times the microwave rated power. All will be well again.

[auskiwi]

Originally Posted by Stu Jackson

Could you please explain inverters charging batteries? That one got right by me....

I guess he means batteries such as phones etc, you cant charge your boat batteries via inverter as power for charger is supplies by inverter, just chasing your tail. Sorry if I have misunderstood you.

[MartinAdelaide]

I'm just impressed by how knowledgeable yachties are about sine waves and electronics.