CORRECTIONS to the reverse engineering as pointed out by some viewers. The mains side isolation transformer is a common mode filter inductor: kzfaq.info/get/bejne/r7V6atuB2s3XlJc.html

Really interesting! I would love a teardown of a different micro inverter! I always think you can learn quite a lot when you compare two different products and check what the two manufactures did similiar and where they differ. That's the interesting part! :D

Those little transformers TR100 and TR101 are actually current transformers to measure the current in the respective switching MOSFET and winding. The current passes through the metal strip over the top of the ferrite core ( primary winding with 1 turn) and inside the core is the secondary winding with e.g. 100 turns. The sec winding is accessible on the two outermost pins on the left side. all the remaining Pins are NC and soldered just for mechanical stability.

I have 17 Enphase microinverters on my roof, installed 7 years ago. Over last 2 years, four of them have failed one by one, which is about 600 times their claimed failure rate of 50 per million per year. I suspect they would have lasted longer in Arizona or Australia, but in wet, humid and often overcast Southeast US, with all the thermal expansion and contraction, you just can't keep moisture out of those boxes no matter how hard you try. Theoretically they are under warranty but kind of a nightmare getting them replaced, because I'm too old to be getting up on the roof and the outfit that installed them is no longer in business. Enphase doesn't like dealing with homeowners anyway, so I have to find a certified Enphase installer willing to work on somebody else's system, not so easy. And the icing on the cake, so to speak - the warranty doesn't cover labor!

Regarding the AC plug - there are essentially two versions: daisy chain (double AC plug) or trunk like this one (you plug it into "T" connector on trunk AC cable)

Dave the TMS320 is a mainstay of solar (and motor control). Especially the Piccolo family. Why? They have a High Resolution PWM (HRPWM) that uses some magic technique to get PWM resolution greater than the clock for very precise mico adjustments. I think it's 150pico second steps (less than 200ps anyway)! I expected to see a TMS320 and lo and behold we have it.

Thanks! I liked the way you did the schematic over the parts. Makes it a lot easier to comprehend.

Looks like its following a Microchip AN1338 app note but using a Ti processor. Basically the two large PQ cores are the inductors for two interleaved flyback boost converters. They are interleave for efficiency. These produce a high voltage DC that is galvanically isolated from the panel input DC by the inductor's secondary winding. The DC then runs to a combined PWM and un-folder stage to produce the AC output sign wave. The un-folder makes the opposite half phase. Micro inverters are current sources not voltage sources. You can't expect your 350W inverter to change the grid voltage but you can push current to the grid. I didn't go through the code but my impression is it adjusts the voltage phase relative to the grid phase to control the current supplied to the grid and to remain within the MPTT range of the panel. The DSP math is quite complex, with several servo loops, PLL's and error checking. All the while running the flyback converters, PWM and unfolder circuits. Lots of factors to consider. Every so often they turn off and check that the grid is still alive and shut down if the grid has failed. Don't want to fry the lineman up in the bucket truck.

That was a cool tear down. A video on how these work would actually be really cool. Ex: how do they sync with the grid, and how do they detect if it goes down. Especially when there are many of these on the grid, how does one inverter not think another inverter is "the grid" and keep going, for example. I presume it goes by current draw, if grid goes down it will try to pull massive current?

I had never heard of Hoymiles before the hardware appeared in your mailbag. Apparently we've all been missing out. Looks like they're ticking all the boxes for safety and reliability. Thanks for the teardown, despite the goop.

I had to replace the relays on a full size inverter that weighed about 30kg. Some scary caps in there, I definitely triple checked they were discharged 👍 Was a very nicely designed piece of kit, very high quality boards in it.

Great video. Watching all the way from Western Kenya.

Great tear down very useful for beginners like me, Cheers Brother.

Good job! Almost can( re) projecting my own device! It was wherry deep!

The electrolytic capacitors store energy to balance the 2x50Hz mains power pulsation, not clouds or birds covering the panel.

Wow thank you for this, I always wondered how that would look like from the inside.

Love your Video. Cried a bit though watching you tearing down a unit, which was very hard to get for month here due to supply chain issues. The educational aspect was worth it, though.

Thank you Dave, I really wanted to see a teardown of a microinverter.

Very interesting teardown and going through the path like that. I would like to see another to see how they compare to be honest.

That goo looked nice, I’m ordering 10 of these. I would love a teardown of a different micro inverter!

I enjoyed this teardown. Pretty popular devices right now.

I add it to my schematic playlist!

Yes. Please review also the other inverter.

Oooobaby can’t wait to watch this later

Thanks for sharing!!!!

To a degree I wouldn't be surprised if the "transformer" Dave suspects to be the main isolation transformer to simply be an inductor. And instead have the two DC-DC converters handle the isolation. And I suspect this to be the case given the two optocouplers top left at 21:30 going over to towards the "transformer". And there is more optocouplers on the back of the board for this region too. The advantage of isolating in the DC-DC ones is that one can make a compact design able to handle high power. And then use a class D output stage to generate the low frequency AC for the mains voltage. Ferrite transformers don't tend to like low frequency stuff, especially at high currents. Tends to over saturate and do a poor job. But this isn't a problem if one switches a class D amp at high frequencies to generate a low frequency signal. Efficiency is typically fairly decent too.

It would be cool to see some testing on these before you tear them down. Hooking them up to the lab power supplies and measuring output waveform and the thermal output at the case would be examples. Maybe also do some over driving of the inputs and see what breaks first?

Interesting black "goo". I have disassembled two IGBT modules at different times. In comparison to your semi rigid stuff, what I found inside was crystal clear stuff (except the black burnt traces indicating electrical tunneling). But, clear or already burnt, it still was sticky and stretchy beyond my belief. The modules were about 6" by 3" by 0.5". They contained a 6 diode 3-phase rectifier bridge and 4 IGBT H-bridge for variable frequency drive and a "bonus" IGBT for a brake. It took me over ten hours to pull most of the goo out with tweezers, forceps, small screw driver and exacto knife. Half of the time was spent on cleaning my tools with paper towels...

More please, I always dreamed of making these as DIY but it is beyond my skill level. This video gave me a rough understanding

Nice to see. There's an HM400 in the very small system that I installed in my daughter's apartment. We have HM1500 on our second system on the garage roof. They seem well engineered.

I, too, would love to see teardowns of different micro inverters to see the differences in design and operation, please! Thanks, KW

Interesting! I was sold IQ7 Enphase from the solar salesman, but the installer wanted to install Hoymile inverters with 4 panels to each. They didn't look impressive from a general overview, and I didn't like their production dashboard. I insisted on getting the Enphase, but these Hoymiles don't look too bad. Definitely would be interested in seeing what the IQ7 inverters look like in comparison!

Yeah! Please do the ZBeny review! :)

I say keep on opening them up until we see something weird/different. Bound to be some gems out there.

yes please, i like knowing the failure points of these ☺

That's the same goo that I pulled out of an Enphase IQ7+ microinverter. Sticks well when thrown at a wall. 🤪 I'm not great with electronics but great explanations of it all!

I would like to evaluate the micro inverters based on emc compliance and testing. In our country basically every imported micro inverter fails to meet regulation and its a big problem!

definitely more inverter teardowns

I wish all potting compound would be like this it would be so much fun.

Input fuses are not needed because the panels are current limited (Isc) so even if you reversed polarity they would not source any extra current to blow the fuses anyway.

My congratulations from Krymia We are expecting for U! Th-x for all!

A few years ago I opened an Enphase microinverter and it was fully potted with the same kind of material. Yup, it liked to stick in components like inductors :) In my case, the potting material seemed to kind of flow back into place with a little bit of heat and time - warmed it over 30 minutes or so on low temp in my "projects oven" in the garage. Looking back in my circuit pics, the Enphase inverters (at least the model I have) don't have fusing in the PV input side either. And they have the same double-transformers that you showed here, so I'll guess the same push-pull "interleaved" drive that you pondered of them. I apparently didn't take pictures of the bottom side where the FETs live.

One more inverter for comparison would be good.

It would be great if you ranked them: for example: temp management via thermal camera, protection for reverse polarity or overvoltage

I would love to see the switching topology of this inverter since me and a friend started our thesis making a 2kw inverter

Great video. I do wonder if the drawing of the isolation transformer is right. It would have to output 240VAC at 50/60 Hz, rated for 400VA. It seems awfully small for this job.

Making the insaney more plainy. Thank you

do some more of them!!!!

My solar installer wired one of my 9 panel strings reversed polarity into the hybrid inverter. Managed to handle it fine, i was impressed. Though it would have at least destroyed the mppt for that string, but no... It's running fine...

3:00 Dave playing with EE play-doh lol.

you can talk to them via an NRF and openDTU :)

Man I have a lot to learn

Thanks for this. If you apply the panel backwards, the diodes in the FETS limits the voltage to -0.7V. I routinely get 356W out of my HM-350NT and they blow away my IQ8+. They're excellent, IMO.

The tiny transformers are CTs for the power switches

oooo this is what I wanted to see: like + comment

Just I recognize that is a HMS version. The models with HM and MI it exist already a opens source project in github (Ahoy and OpenDTU). With that you can read the inverter and control it. The HMS use a other frequency (868mhz) and it is in reingeneering process already.

Please consider working another micro inverter for comparison. I'm using Enphase on my panels. Thanks for what YOU do. ...N3JLR

Single phase AC has a sine^2 power profile where the PV panels need a constant DC load to provide maximum power. You don't want 2x AC line frequency power flow ripple current to show up on panels or you lose power from PV panel. That is the reason for all the electrolytics across PV inputs and the weak component reliability link in the micro-inverter scheme. Electrolytic caps MTBF is highly dependent on their operating temp. Micro-inverters operate in a very hot environment behind PV panels, likely a few inches from a hot roof. Not great for electrolytic caps longevity.

It is, in fact, a differential mode filter to filter out the switching harmonics.

The DC output of the solar panel is not as clean as you want it. They actually have a fairly high source resistance. I forgot how many cells you have to have in series to get 60 volts. Adds up to a lot of slop in the voltage hence a lot of beefy caps to smooth it out. What kind of current pulses do you have at 400 watts?

That thermal 'putty' would be nice to identify and source.

ChargerLab channel just did a teardown of the Enphase IQ7+ micro inverter today. It must be a trend! 😆 Their layout seems a bit different, but they also use a lot of input capacitors.

I would like to see the other teardown

Is that mains side correct? I thought you weren't supposed to put GDTs directly across high current protected lines because once they light, they may not extinguish. I always heard that this was a common failure so MOVs are put in series with GDTs. Maybe the GDT is in the center and goes to ground, while the other side goes through one MOV to live and another MOV to neutral?

Please do that other inverter teardown.

more and more ppl is ordered to shut down there solar systems here if they use inverters of that type (one for every panel) they make so much radio noise together that they shut down airport radar and other communication systems. yes they complies by itself.. many of them together do not.

Certianly. Some of them have a bit of an iffy rep. I was thinking of getting 3 of these for the 3 spare panels I have. However the cost!! So I bought a Solis 1 KW inverter 2nd hand. (As new under speced by an installer) so it has only a few hours of use. This will tie in with my 5 Kw Solis inverter. It wiĺl run 4x 260w panels so I can add another panel if I want. It cost less than one 300w micro inverter so all good.

Assuming no ingress, what do you think would fail first? (My bet is a 65V max input rating could age those 63V input caps. I like to see 100% margins on input/output caps.)

The square device on top of the AC side MOV is most likely a thermal fuse in series with the MOV to guard against short circuit failure of the MOVs. Quite typical arangement for surge protection. Will isolate a MOV that has failed low impeadance. You loose the surge protection but it shouldn't catch fire. Safety feature rather than functional benefit.

That potting compound looks like a goopy silpad!

My son's friend is a lineman. Protocol states that each primary phase must be grounded before any work can be done on the conductors. However, it is interesting to note that no such protocol exists for the stepped down 240V residential connections to the distribution transformer. As more and more solar go online I think these rules need to be changed.

Those Caps are called DC-Link capacitors, mainly energy buffer und reduction of current ripple, a common thing in Inverters 👍

Theres an open source solution for the wireless protocol with an ESP32 and some wireless module as a bridge. Got it running, works like a charm and only costs cents!

It would be unusual to fit a spark gap over the top of an MOV, it is more likely to be a thermal sensing device to check if the MOV's are getting hot through over voltage.

Though I couldn't see the look on your face while you depotted this thing, I could practically *hear* the gigantic grin.

Hi Dave what great timing , I was looking at these for my new installation. I have heard these units run bloody hot even when ambient is under 30 deg C , this worries me for longevity when compared to Enphase. What have you heard and your thoughts. I was also lucky enough to meet you at Norwest mall a year ago, keep up the good work. Cheers

The h-bridge drive after the flyback looks like it might be a full bridge driven LLC converter? - hence the two caps, one for DC, one for AC resonance. Did you check the pin connections there?

Back when I worked on inverters the TI chips had much faster and more capable ADC which made the control software easier to write.

There was a fireman that died in Germany due to DC arc over a few years back. Since then they have to check the solar panels before starting the fire fighting. Note, that even if its in nighttime. Just the back light from the fire, might charge up the panels to a considerate voltage, even if there is hardly any current. This is a problem, because if your house is on fire... for some other reason, and they can´t verify that your pannels are AC or low voltage DC, they will not save your house. (well.. they might if its just a minor fire, but if its a big fire and they have to spray the whole house)

Those axial power resistors are pretty high spec for carbon film jobbies - 2% tolerance, 25 ppm/K. Very not bad.

I'd like to get a deep review of the HMT-1800/2250-6T though.

I think they are using two 180 degree interleaved step up converters and than make the AC which they then step up to 230ac using that other output transformer. That could be, instead of using two fkyback with all their disadvantages vs step up in CCM.

The little RF communication board has its own FCC ID ...

If installing one or two PV panels say just to supplement a few watts grid tied , dose Hoymiles Micro Inverters need the gateway to wake them up like Enphase micro inverters ?

Definitely get the other micro inverter for comparison. How do these thing’s synchronize with grid frequency?

High frequency High voltage side via Trough relay!

So gas discharge between the mains, and another between mains and ground. Good protection in case the mains are subject to something harsh, like a lightning strike?

Can you do a video where you go into detail about circuit protection like with MOFs etc? I know little about what you can do and should do. There was sadly nothing lectured in university despite this maybe being the most important thing when designing an electric device… Also would be great if someone could recommend some existing tutorials.

I know someone had anti-islanding fail because two different inverters fed the grid keeping each other awake. Aishi caps are used in CFLs a lot._

I don't think, that the transformer on the top (AC-output) is an isolating one. It's too tiny for 400W @50Hz. I guess it's a filter in mH range.

In this episode... Dave plays with silly putty! :D

That is a pretty cool (pun intended) solution for something that is not needed to be opened..

Hi Dave, I wonder how mains sense works. How it can differentiate mains coming from grid from mains coming from another micro inverter? Can it be fooled by lets say UPS?

Nice something)

Sure review all the Micro inverters! put them in service for a view years... Free solar...

a TMS320 that is a surprise

Please review enphase IQ7

Dave playing with doh play putty, game on.

I Have The Bell On And I Have Notification On. and Most time I Never get IT. Or I got this one a day late

16:40 Mains Voltage, Mains Frequency but no discussion about Mains Phase. Is all power added to the grid as Voltage (Amplitude) or does it ever use leading Phase to increase frequency back towards 50/60 hz. Would be nice discussing how the Grid goes down and the response of microinverters as Voltage and Frequency drops.