A Microwave Oven Transformer, but switching! 

I guess that inverter microwaves didn't take over because the iron core transformer is more reliable.

I have seen ovens trashed by the same. Designers, please fuse your bulbs!

@@Alexelectricalengineering or maybe cheaper than a switching supply? I mean, nowadays the MOTs have the absolute minimum amount of metal in order to work. Nothing like what they used to make...

Well, the inverter side needs actual copper wire in the unit, while the iron transformer just uses CCA wire. It is a lot cheaper to stamp out iron laminates, and wind the CCA wire on formers, on machines long since paid for. Low cost materials, low cost labour, and as you ship by sea volumetric mass is the rate used, as a microwave oven is almost all air inside, even with a 2kg lump of steel in it. The inverter ones are only used where you are paying much more for more precise control, as they allow cycle by cycle PWM switching, so instead of the iron core having a PWM over a 30 second repetition period, you now have it based on the input mains frequency from the control panel, so the apparent power delivered seems to be much finer, as it is being adjusted either 100 or 120 times a second, per cycle power limiting.

And yes, even on a regular microwave that lamp blowing can take out the 10A ceramic fuse, I have changed many fuses along with the lamp, and modern ones now also use an 8A fuse in 230VAC countries, as it is cheaper, and include a soft start circuit to limit the inrush current into the transformer as it turns on into a cold filament of the magnetron, or with the duty cycle switch turning it off for a few seconds every half minute.

The switching power supply is much lighter than the iron core transformer. Much cheaper to ship. Money saved ... that is all.

@@chuckvoss9344 Not in a microwave, where you pay volumetric mass, as the cavity is all air.

Microwaves with these power supplies are inverter microwaves, which aren’t subject to the long-period on/off duty cycles to deliver partial power. In other words traditional microwaves with normal transformers run full-power for 5 seconds and then zero-power for 5 seconds, to provide 50% power. But microwaves with this kind of power supply do not have these long-period duty cycles to achieve partial power. So it actually is “progress” if you care about heating food more smoothly.

My guess is you could have a decent switching supply that would last the life of the microwave, as long as you don't skimp on decent parts and have sensible board design.

@@HobkinBoi I will say that in general the iron core transformer is generally really reliable. They do fail with shorted turns with the CCA wound ones, and a replacement is as expensive as a new microwave, so the good ones from scrapped units are pressed into service instead. I have scrapped more microwave ovens for the cavity rusting through where the turntable runs, and, for the recent few microwaves, the failure was the actual RF filter assembly on the magnetron arcing over internally, which is a really odd thing to have, as those are pretty much just a thick ceramic tube, with silver plate on the inside and outside, potted in hard resin. I guess they are using cheaper materials there, leading to the failure. Despite the high power it generates, the only failures in magnetrons is from the output probe arcing over from dirt in the waveguide cavity, from the mica or RF transparent plastic cover either breaking, or being dirty and burning up. Only ever had one fail due to age, but seeing as it was 30 years old, and went low output, it had definitely done well. Replaced with another used one, that was younger by around a quarter century, and in good condition, with the right fin and mount orientation. Also had one fail with a broken filament, but to be fair that oven had taken a trip off the table to the floor before that.

Not me, they use less power and the Toshiba ones made by Midea last LONG time, and cheap to fix yourself.

For his schematic it was clear that it isn't a half-bridge, as he claimed. You confirmed my suspicions that it is resonant and that the upper IGBT is an active snubber. It is nearly impossible to achieve low leakage inductance with a transformer wound in that way, and that winding design is pretty much essential to for the voltages involved without running the cost way up. My guess is that the leakage inductance is used to advantage in the resonant circuit.

if the heater goes open, there's still the low voltage winding.

I'm looking at it musing if I can use it as HV supply to build a ham radio tube linear power amplifier. 😂

Yep, I tore apart a Panasonic microwave as a kid looking to tempt fate with some microwave oven transformer experiments and was disappointed when I was met with this style of board. Probably for the better that I wasn't able to mess with high voltage lol

This is a standard module, introduced in the 1990s and in use in almost every brand of microwave ovens.

when first powered ON NOT when first powered on. When referring to SWITCHING It is to be written ON / OFF ( In ALL CAPS ) and not on /off The words sound the same but they are used in different contexts - and had you been TRAINED to pay attention to detail - you would have noticed that it is written correctly on switches. Unfortunately the majority of people are programmed to be ZOMBIES ZOMBIES have eyes but cannot see - ears and cannot hear. The eyes see one thing and the brain sees something entirely different You have to reprogram the brain to pay attention to detail. Your corrupt School system did you more damage than good.

@@andrew_koala2974 Ok, care to explain what the difference means?

​@@andrew_koala2974 After 13 years teaching and 30 years in the military, I would be on the assumption that your life would have come to something better than flaming person on simple comment on a RU-vid video. I know life might have become harder for you after your daughter left you to go work in NYC, usually people can fall into a spiral of depression and sadness after they children have left them but for you I think it has led you to fall in a spiral of mental insanity. Previously one of your comments on one of your videos flames a simple comment voicing their opinion about the music choice, but no you had to attack that person for a simple missed correctly spelt word 'your' instead of using 'you are'. Many highly acclaimed people unlike yourself do not solely focus on ones spelling but the context and reasoning behind their comment. Around the RU-vid community uploading videos in 720p is not acceptable for viewing, 1080p is the standard in the community but yet after your 13 years of teaching English and History and 30 years in the military it would be assumed that you would understand the RU-vid Algorithm and see that uploading in 720p is not beneficial and almost every current phone can stream and most can even video in 1080p or even a higher resolution, so after your RU-vid videos in the past year don't even bring in an average of 30 views but your mentally insane brain can not comprehend that less than 30 views in not good performance. Any normal person would either give up or change the way they produce and upload their content but you brain does not understand that you should change your videos or give up. To Summarise you have passed the line between insane and normal. Flaming people's RU-vid comments is not acceptable or healthy for anyone. Go put close RU-vid and hide in Sydney, and leave all these peoples RU-vid comments alone.

based@@andrew_koala2974

@@andrew_koala2974 👍🏻👏🏻💪🏻

Most Panasonic microwaves are now made by Midea. You have to look well to get a true Panasonic

@hardstyle905 LOL Lots of Love

@@MieleW2573 CORRECTED FORMATTED TEXT Most PANASONIC microwaves are now made by MIDEA One has to look well to get a genuine PANASONIC You still have to learn how to write CORPORATE Names correctly and hoe to format text into paragraphs. You must have missed a lot of School or fell asleep in CLASS. So pay attention to detail - and learn that all CORPORATE legal NAMES are always in the ALL CAPS iteration. Now do your homework and explain why that is so.

Some people just want to be the victim constantly.

Uuum, ZVS ? Zero Volt Switching ? I have a bad memory...

yep. @@snakezdewiggle6084

@@snakezdewiggle6084mazzilli ZVS driver

I think they mean the self-resonant soft-switching current-source converter that was popular on youtube for a while. Self resonant so the magnetics are not ctitical, Soft switching, so it has high power handling.

Ooo I am interested, can you maybe show me the schematic?

Well, this also came to my mind, but the two points are still connected via the low voltage secondary.

That's right, maybe they chose this way because it was easier to connect, since the doubler capacitors are mounted on the side of the bobbin?

It won't amit any other radiation. With a cold cathode, you have no current. Magnetrons do produce X-rays in normal operation, but 4 keV is too low energy to pass through the copper anode. Even a thin glass vacuum tube will block X-rays under 10 keV.

@@mernokallat645 You're right, I didn't think about the low keV, but magentrons can produce X-rays when the filament burns out but is still hot enough to emit some electrons. You will get a hotspot which will give you enough electrons for a accelerated path inside the tube. Once you disconnect it, it cools down and then will never generate anything again. Correct me if I'm wrong... I thought the beryllium stem of the antenna was quite 'translucent' for X-rays?

@@SunnyJulienDivine I tried disconnecting the heater and it stoppe emitting microwaves in a few seconds.(With the high voltage still connected). The beryllium oxide or aluminium oxide insulator is still a few mm thick. X-rays tubes with thin beryllium windows rarely emit under 7 keV.

There's a warning at the beginning of the video. There's a warning in the description. There's a spoken warning when I test the MOT. And there are the calculations that also give a lot of a warnings and scare the hell out of people. If it's still not enough, I don't have much hope for humans...

@@DiodeGoneWild I know, looked to me like the text before all the vids here. No offense intended, these things just give me chills.

@hardstyle905Point is, there is no room for error, you are just kill. It's riding a bicycle compared to riding a 1000ccm super sport. I never got an electric shock except cattle fences, and I played with tubes, and messed around working in big solar parks.

@@timtim8468 Microwave Ovens of any design are without doubt the most dangerous and lethal home appliance ever invented.

@hardstyle905 These Teens have not read a BOOK since age 5 They can neither read nor write correctly and they have the attention span of a house-fly

Gotta love those duck shin overs.

türk varmış ya bu adami izleyen, bende tekim saniyorum

Skip the transistor and use a vacuum bulb for more fun.

just a ZVS or even better if you wanna do an NE style, a TL494, much better for audio modulation problem is that the voltage is really, really low compared to a CRT flyback so it will be hard to maintain a stable long arc especially for audio modulation

@@BH4x0r You mean the output voltage OR the amount of current you need to drive that transformer, which makes the voltage low?

@@TomboRectify i mean the output voltage, these are made to put out approx 4kV at high current, just like the metal transformers (the metal transformers go through that capacitor and diode as a half wave voltage doubler), a TV flyback from an actual TV puts out anywhere between 20-35kV (dependant on TV size) on the stock driver

Why don't YOU try that? I swear I would love to see that :D

I gues the heater voltage doesn't vary that much, because the main load is the anode-cathode current, that doesn't affect the voltage drop much. The magnetron simply tends to drop about 4kV no matter the current. This clamps the transformer voltage per turn to a sort of constant value. The anode winding is probably between the primary and the heater winding for this reason. The anode winding is like a bi-directional zener on the heater winding :).

I just tore apart my first microwave magnetron, I used my 4" grinder with a thin metal cut off wheel and was wondering what the different metals are inside? Was thinking that a magnetron could possibly be used as a spark gap.? I heard somewhere that a magnatron is actually a diode. Is this correct? Just watched a vid of someone blowing air up a Jacobs ladder making a plasma flame thrower basically. Thanks for all the videos, recently found your channel and appreciate you sharing your knowledge.

I'm guessing you mean the price? I've been out of MWO repairs for quite a few years, but I randomly Googled and (being in Australia) an LG inverter for many of their models would cost AUD99.95 (USD65), including Tax and without any trade discounts. LG prices are pretty good, inverters for other brands like Panasonic or Sharp would cost more. But as usual with electronics, volume production lowers costs.

At work we have a Siemens microwave built by Panasonic. It’s an inverter as well, made in 2000

@@MieleW2573 oh nice!

Panasonic released their first volume production domestic inverter MWOs in 1988. I'd been a technician for 13 years and had to learn how to fix them.

afaik all you need is a pwm signal at the input

Yes, the rework program. When the Panasonic Inverters were released in 1988 I had been a technician for 13 years and ran the service department for an electrical retailer.

They use a power wave envelope scheme similar to an induction cooker, also it uses a handshake signal from the control board and that also tells it hey set the power to xx.xx%. It also tells the control IC that all is well at 120 or 100hz. The most common fault with these are the rectifiers that do not seem to be truly designed for HF operation.❤

@christopherleubner6633 Yeah, called an Error Amp, and Feedback. Handshake is just another term for Successive Approximation.

Isn't this more like an LLC/LCC converter instead of forward?

Yes, this is exactly what I also noticed. Perfectly impedance matched to a human :). Or at least matched to the center value. The transformer is 1000 ohms, the human starts at 1500 ohms an gradually reduces to 500 ohms as the skin turns into carbon.

Interestingly a higher current like 1A can be sometimes less dangerous than 100 mA. With 100 mA, only some of your heart muscles stop, making them out of sync. A higher current stops all your muscles and if your heart restarts it is more likely to restart in sync. A defibrillator deliberately stops all heart muscles for this reason.

Maybe a flyback topology? Not sure but I have seen microwave inverters with single IGBTs and dual (but different) IGBTs.

@hardstyle905 It may be a single-transistor forward converter, some time ago I tried to replicate a Soviet scheme of an inverter welder with this topology, which uses a regenerative snubber in the hot part of the circuit. I don't know if it has anything to do with the microwave inverter.

Yes, at such a low frequency as 50 or 60Hz, you primarily need the permeability to be as high as possible. Ferrite has a much lower permeability. Even with iron, the cores still have to be big and the numbers of turns high. On the other hand with tens of kHz, cores are small and numbers of turns are lower, but the core has to have low losses (hysteresis and eddy current) at such frequency, so iron is unuseable, ferrite works much better.

He was holding a ground wire, not the HV side.

chad mot@hardstyle905

Panasonic? It was a known fault for them.

@@PlatypusPerspective yep, exactly!

Meh I wouldn’t really call these “expensive” because the flaw in this statement is that the price will naturally drop overtime- but yes they are for now. Inverter microwaves.

"The ones that don’t need to switch on and off at lower power settings" Yeah, that's inverter microwaves. The ones without a turning glass plate are usually inverter but they don't have to be as they use a regular magnetron pumping RF through a waveguide into a chamber with a turning metal disk located underneath the floor of the oven, which is what eliminates the need for a turning glass plate.

@@albatross_v2 Thank you very much!

@@Conservator. No worries. I've seen you comment on this channel for quite some time.

Inverter microwaves can modulate, but only to a certain level. Since the filament voltage comes from the same transformer, it would drop to low They usually operate continuously down to around 50% of power. Beyond that, they cycle on and off like a normal microwave does

Depends on the size of the screen :). I noticed on a laptop, but probably looks fine on a phone.

@@DiodeGoneWild I actually watched on my pc, but not the highest quality. Either way, some blurriness here and there is not all that detrimental to quality and educational value of your content. Audio, at least for me, has a much bigger impact.

It's NOT a standard half wave bridge rectifier. One halfcycle charges the capacitor and then the voltage of the capacitor is added to the other halfcycle. It produces a pulsed voltage, not smooth DC.

He was actually holding a ground wire.

It doesn't matter because the transformer in question has no connection .. electrical or (static@50Hz) capacitive to any earth/grounding and most importantly the other hand or no body part is in physical contact with the other bare wire.

@@analoghardwaretops3976 I think that's a dangerous statement to make because of the voltages involved. The primary is most likely not insulated for 2kv, so if you touch the high voltage lead to real ground the transformer core will go live at high voltage and it could arc over to primary.

@@eDoc2020 50/60 Hz Tx. under test..one can clearly see the pri. & sec.are wound on two separate bobbins. & printed schematic shows an isolated stepup secondary. So question of pri. " isolation " doesn't hold..besides all testing has been on an insulated work table... Even feeding the pri. through an additional 2/3/5kV isolation transformer will be of no more saftey than this demo setup. Usually wires for 2-3kV voltage potential will have insulation that has to withstand at least 7.5-10kV b.d.v. besides to comply with safety standards...engineers/ designers will have considered most of " your " IF's & BUT's doubts before a product evaluation /release. so D.G.W. is very capable and cautious & also knows the consequences..and has taken sufficient precautions for this demonstration.

​@@analoghardwaretops3976 Sure the secondary has good insulation but the primary is only intended for 230 volts. I agree what DGW was doing was safe, I was just pointing out that your comment could lead to disastrous results if people used it as general safety advise for their own experiments.

The inverter microwave I'm familiar with blanks all wifi in the room, there's a home theater remote speaker in the kitchen that uses 2.4ghz and you can hear the audio break up as the cathode comes up to temperature. Worth it for the true variable power and higher max power.

Yes, MOTs can surely be handled way more safely ;). SGTS is quite loud and smelly, so I also prefer SSTC. You can play with it longer before it becomes unbareable ;).

Don't forhet to ballast the MOT. You can use 3-4 40-65 W fluorescent lamp ballasts in parallel.