Microwave oven start challenges. Arctic Fox 811 with 900W microwave, two Renogy 100AH in parallel with 2AWG 8" jumpers and 1/0 cables to AIMS 3/6KW inverter will not start this little microwave, but will start the roof air conditioner! Swapped it for a 30 year old, new in box 1500W modified sine wave and the microwave starts and runs no issues! I can do some fancy footwork and start the oven on the AIMS by hitting pause while it is growling at me, before it goes into overload, and then immediately hitting start again. It then will start and run so I believe it's the in rush current needed to charge its cap. Aims refunded and I purchased a new Giandel 2200/4400, this ad he AIMS look like the same Chinese board, but shorter with less SCRs due to its lower power, but it does the same thing. Purchased a new 900W oven from Walmart and it started a few times, but then did the same thing. Moved the 2200W inverter right up to my truck batteries, (240A dual alt) and same thing. Seems strange this issue is not all over the internet!
Microwave oven issue on inverter
- Thread starter mspenc45
- Start date
Rider
Solar Addict
It does sound like an inrush issue. Never tried one of these, but maybe?
Rider
Solar Addict
It will work on anything, not just a/c, and soften the start.
gnubie
Solar Wizard
- Joined
- Sep 20, 2019
- Messages
- 3,847
It would be interesting to see what the DC input to the inverter is doing. I have a Giandel 2000w pure sine 24v / 240v inverter and it starts my heavy transformer based microwave without problem, while simulatenously running this PC. The oven puts away 1.2kW with the magnetron on.
HighTechLab
AKA Dexter - CTO of Current Connected, LLC
- Joined
- Sep 23, 2019
- Messages
- 1,705
Get your self a clamp on amp meter that can measure AC & DC amps on the clamp and set it to hold the maximum current. Clamp it on the output of the inverter or the input to the microwave and see what the maximum amount of amps AC the microwave is drawing. If it is out of the specification of the inverter than I would suggest a bigger inverter. If it's smaller than the inverter's ratings, move the amp meter to the DC side and set to hold max. See if this rating exceeds the amperage rating of the wiring feeding the inverter. I suspect there is too much voltage drop here.
Let me know your findings.
Let me know your findings.
Two false starts here, then a good start. I found that I could fool both inverters into starting the microwave by starting, stopping, and then immediately starting the microwave again. 2/0 cables at only 30" length. The fact that a lower output rated modified sine wave can start the same microwave under all the same connections and variables seems to indicate to me that these newer Chinese models lack some sort of instantaneous surge capacity. FYI, the if I measure the output of the newer inverters, both the AIMS 3KW and Giandel 2.2KW, the output voltage drops all the way to about 62VAC when the microwave fails to start, but on the occasional proper start, the voltage only drops to about 95VAC. ALso, I moved the Giandel right up to the truck battery with engine running and 12" 2/0 cables, so again, I believe the problem lies within the inverter. A 24VDC inverter I would have guessed would not fail as the 12VDC has. Just not sure what has changed in 20 years and moving off shore. Here's the DC:
H
gnubie
Solar Wizard
- Joined
- Sep 20, 2019
- Messages
- 3,847
Direct HF inverters are well known for having pretty much no surge capacity. They all come with nice big colourful stickers saying they have twice the rated continuous output available as surge but if you look into the statistics they can only maintain that higher rating for milliseconds as the voltage on the high voltage rail quickly implodes.
In order to avoid blowing up the output transistors most of them employ so called soft-start. It's not soft start, it's really soft regulation. Throw a big load on them and the output plummets and then slowly climbs back up. That big load could just be the input capacitors on a cheapie wallwart/plugpack.
Running any high inductance load on a modified sine wave (modified in much the same way that a bicycle is a modified car) isn't a good idea. Microwaves that use a big lump of a transformer to produce the 2kV supply should only be run off a proper sine wave supply.
In order to avoid blowing up the output transistors most of them employ so called soft-start. It's not soft start, it's really soft regulation. Throw a big load on them and the output plummets and then slowly climbs back up. That big load could just be the input capacitors on a cheapie wallwart/plugpack.
Running any high inductance load on a modified sine wave (modified in much the same way that a bicycle is a modified car) isn't a good idea. Microwaves that use a big lump of a transformer to produce the 2kV supply should only be run off a proper sine wave supply.
Rider
Solar Addict
I have an AIMS 1000/2000. I was emailing with their tech support, and I was told that the "2000" watt surge rating was only good for 40 milliseconds. That would tend to support your thought that there is no reserve capacity.
That is exactly what I suspected. Soooo, what brand or model of built to truly handle their advertised surge load?
gnubie
Solar Wizard
- Joined
- Sep 20, 2019
- Messages
- 3,847
Only the expensive well built ones in the class of Victron and better. The cheapies, no matter what their design, simply do not tell the truth about their rated output, surge or continuous. A properly designed direct HF, intermediate HF, or fully LF, inverter will work. There is no inherit limitation in the concept.
Now if you don't mind getting something with lower rating than what is on the box, you can get cheaper LF type inverters that can do the job. Even the legendarily crap Powerjack LF inverters will actually do the job, so long as you halve the ratings.
Now if you don't mind getting something with lower rating than what is on the box, you can get cheaper LF type inverters that can do the job. Even the legendarily crap Powerjack LF inverters will actually do the job, so long as you halve the ratings.
Rider
Solar Addict
Could a bank of large 12VDC capacitors, like car audio enthusiasts use, be helpful? Then you could use just about any inverter.
Challenge is that I've gotta keep it in the form factor that the lower quality one are in for it to fit in my pantry.
Getyourbone
Hard to offend but hard to bend...
Get a different microwave?
Actually tried that. Purchased a similar sized 900W from Walmart and it in fact worked a few times and then behaved the same. I've gotten word from several folks that the Xantrex PROWatt 2000, or this unit will both start a microwave: WRELZB Reliable 3000W High Efficiency Pure Sine Wave
PHoganDive
Solar Enthusiast
If you look at the volt vs watts where the oven first turns on, you can see the watts departs noticeably from the volts, and is much greater. This indicates a power factor issue, Microwave ovens have a BIG transformer in them that steps up the AC voltage to a high voltage to run the magnetron tube. The magnetron tube is still a tube, like the old time vacuum tubes, and takes a few seconds to warm up. Before it does, the load presented to the inverter is the inductance of that big transformer...without the magnetron drawing power, there is a big phase shift between voltage and current, which is likely what the inverter is having trouble with. Once the magnetron warms up and draws power, the phase shift reduces and the inverter can power it OK.
Now that is interesting, and makes sense and is a plausible explanation for the start up load and "fooling" the inverter. I wonder what it is about the different inverter designs, however, that allow some inverters with lower ratings start the microwave without issue. I think gnubie might have nailed that one.
MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
Gowise makes decent inverters at a good price. My pure sine Gowise 1500/3000 surge runs my 700watt micro but I’m waiting on a bigger battery. I currently only have a 55ah LiFePo need bigger. 100ah Ruixu is coming hopefully soon. The next size up is the Gopower 2000watts/4000 surge for not that much more $$.
Best price is on Amazon.
Best price is on Amazon.
