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stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 09:08pm 24 Jun 2019
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hi all i have a 3000w hf inverter that i am trying to repair.
i bought it as possible faulty. it was, replaced 2 igbts and 1 mosfet and all was good for 3 weeks solid. powered everything i threw at it.
the trouble started when i switched it off to mount it on the wall. switched it back on... no output. 2 shorted igbts.
replaced these, pop. all 4 this time.
got a replacement spwm board from the manufacturer and replacement resistors and diodes. switched on, no output, then bang, a gate driver exploded on the spwm board.
so i thought i would try an egs002. popped it in, switch it on, no output but the transformers would buzz for 3 seconds, then stop then try again.
no shorted igbts and resistors and diodes tested good. so i bought a usb scope. the egs003 had 1 bad pwm output and 1 band spwm output. so i bought yet another, popped it on the scope, before putting it in the inverter, all seamed good. out it in and ..... nothing. 2 more shorted igbts. WHY? i had a good reading on the scope. the igbts are the same as supplied from factory. the pinout on the egs002 is the same as the factory one. where am i going wrong? everything replaced with new but it still keeps going bang (never a load connected i will add).
oh and the dc-dc side has always had a good steady 390v dc supplied to the igbts.
any thoughts?
thanks in advance
BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961
Posted: 01:40am 25 Jun 2019
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Lots of smart people on here and you might get an answer
But everyone on this form that I know of do not use high-frequency inverters I only low frequencies inverters
The low frequency inverter like people build on here are pretty cheap and very reliable and can start gigantic loads
Lots of other people have already built them and have posted there build so you can follow that
Sorry for no help but I might have help you out more than what you think if you decide to go to low frequencybe warned i am good parrot but Dumber than a box of rocks
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 06:52am 25 Jun 2019
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I would change to low frequency if budget would allow. My inverter was cheap second hand. And work fine for 3 weeks solid The spwm h bridge topology is surly the same as for a low frequency, only running lhigh voltage. Not low voltage.
Shoot trough is the same at any voltage (I guess) so I’m sure someone must be able to advice why me on my I keep blowing IGBT’s on a factory built circuit board.
renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678
Posted: 07:51am 25 Jun 2019
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And you're surprised that it's having problems?
I don't know of anyone here that does HF repairs.
Mostly that type are the same rubbish ebay design that you just toss when they go bang..... not worth fixing.Cheers Caveman Mark Off grid eastern Melb
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 05:49pm 25 Jun 2019
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When I say cheap. I mean cheap because it was pre owned.
Surly a hf and a lf inverter IGBT h bridge is the same. My dc-dc side is working fine. It’s just the dc-ac side that keeps blowing IGBT’s Edited by stockleys 2019-06-27
LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 06:36pm 25 Jun 2019
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No.
They have very different design requirements. They might look the same from the block diagram perspective, but you could not, for example, swap in a lf inverter IGBT h bridge into a hf one.
If you want a system that you can diagnose and fix yourself, go LF because it requires less engineering skills to do so.
The trade off will be higher costs in materials.
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 06:49pm 25 Jun 2019
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More cost and more space required. I don’t know where I would get a transformer large enough for 3kw here in the uk. Any ideas? To be honest, iv spent so much on IGBT’s trying to get this working again, that I might as well have just paid it to the electric grid. Pretty much had enough now. And to go and build an inverter from scratch with the chance of that also costing a lot in potential blown IGBT’s, I don’t think I fancy it.
Today I fitted 4 more new IGBT’s along with all new resistors and diodes. And fitted another new egs002. (Which i scoped first and all was good). But yet again it blew 2 IGBT’s on output 2 high and low. But not the 2 on output 1 high and low
tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 438
Posted: 06:50pm 25 Jun 2019
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I wish there is a model number. Better still there are pictures and some sort of reversed schematics to help me understand.Edited by tinyt 2019-06-27
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 06:59pm 25 Jun 2019
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The manufacturer won’t release the schematic. But the dc-ac side is exactly the same as supplied in the egs002 manual bar a few slight differences in resistors values
It’s a reliable 3000w. 12v 50hz 230v
LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 07:08pm 25 Jun 2019
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So think whether there could be a solution that uses multiple smaller transformers than one large one.
We have one right here called the Warpverter. The design principle scales from 300W to 30kW and beyond. Infact, high power designs have to use multiple smaller transformers because one large one simply becomes a practical nightmare.
Why do you think the IGBT’s are blowing up consistently?
Bad parts?
If that was the sole cause, putting in new or better parts would fix the issue immediately - but does that seem to be working?
Or is there an issue at hand that's causing them to go out of spec and self destroy?
The only time HF makes sense is when you were making thousands of them at volume.
Designing LF inverters is hard enough. There's enough evidence on this very forum that shows the total time and effort investment behind a HF inverter, where each and every detail about the parts are known and understood, overshadows the same for LF inverters at ultra low volume.
If I were you, I would start reading up on the Warpverter, understand the design, ask questions and learn how to make the transformers.
That would be the hardest and most expensive step about the Warpverter.
If you're still invested in this particular HF design, tinyt has suggested the next logical steps but I would have not gone that route. Next time it explodes, you are back to the grid and praying replacing the same parts makes it work again.
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 07:23pm 25 Jun 2019
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I don’t know why they keep blowing. Like I said, everything between the egs002 and the output has been replaced like for like. Apart from I used IGBT’s that have an extra 15a capacity. Bringing them to 75a. Rather than the factory 60a. These 75a IGBT’s worked great for 3 weeks until I switched it off for 20 mins to mount it on the wall.
The dc-dc side works flawless. Steady 390v dc at the rectifier
The egs002 is getting 12.36v. And 5.07v consistently.
There is no load connected to the output
What could possibly be causing the shoot through? When every component has been replace with like for like.
I am contemplating the LF route but I won’t be in a financiall position to do this for months now.
Would this transformer do the job? https://www.ebay.co.uk/itm/Toroidal-power-transformer-3KVA-240v-0-7-5v-x-4-400A-or-0-15v-200-amps-PSU/123672682927?hash= item1ccb7761af:g:69cAAOSwpHtce51Q
I would prefer to get my current inverter working though. As it’s a clean, tidy unit taking up little space in what is already a cramp 1 bed bungalow with 2 adults and a new born
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 07:25pm 25 Jun 2019
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I have tried to upload some pictures, but they are all to large.
LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 07:49pm 25 Jun 2019
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How much power are you actually using?
Do you have datapoints that show your average and surge demands?
Use imgur.com
3000W at 12v - I don't think that's the foundation of a reliable design at all.
A reliable design should reduce the stresses on the system at its extremes.
otherwise IT WILL reliably fail.
That Reliable inverter company - there are some teardown videos that go into detail.
You cannot beat physics:
3000/12 = 250A.
If a conductor had a respectable 10mOhm resistance, the power dissipation at that point would be I * I * R = 250 * 250 * 0.01 = 625W
Why dont you focus your energy behind building a 6000W inverter at 200v input instead?
What value does the 12v design buy you?
One possibility is because most popular designs out there use legacy 12V batteries from a time when not a lot of R&D into batteries were happening.
Those designs are now being sold for cheap because smart people are getting rid of them in a market when other people have not yet caught on the changes that are happening.
They are not only cheap because they are used but because they are on their way out.
A 2 year old Android feature phone is not only cheap because they are used but because they are essentially useless today.
Yes it starts up and connects to WiFi, but when you actually check your email with it, you can't even reply to that email fast enough.
It served its purpose to get your feet wet, now it's time to move on.
As more vehicles go electric, the decline of 12v car batteries is assured, the demand for these systems are sure to fall rapidly.
For those still tied to the legacy system, they will have to bear the increasing costs until finances force them to migrate to more efficient systems.
The last few years have completely changed the landscape.
EV and Solar banks has accelerated the R&D that go into batteries today.
You can purchase 2.7V@40Ah LTO batteries incl. shipping for $50 today.
They have a 400Ah surge rating and 10k tested (not claimed) cycle capacity.
If you buy a batch of 1000 of them, the pricing will fall to $25/pc and you have a 270V@40Ah (10kWh!) capacity with a 400Ah surge rating.
It will start your fridge, AC, what have you.
Even if you used up 10kWh every day and discharged them right down to 0, the batteries should last you 25 years.
There's atleast one member here who's done that already. I dont have their permission to share details yet but look around.
This might not be the answer you want but it looks like you need a system that continues to work for you allowing you to enjoy time with your family than spending time and money replacing parts.
You can continue to invest time behind the past or into the future.
In either case you will end up with what you want but it might not be what you need.
tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 438
Posted: 08:15pm 25 Jun 2019
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Do you have utility software to convert to a lower resolution to make the file size stay within the upload limit? Not too low that we might miss some important details.
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 08:16pm 25 Jun 2019
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the reason for going 12v is because when i was looking for an inverter, i already had 12v wind turbine, 12v solar panels and 12v batteries. rather than look for a 24v or 48v inverter then replace everything else i already had, i went for what would work with what i had. buy one component rather than buy all components
daily usage i could not say as yet as i never got around to metering my use (not all loads in the house will be connected) but my peak demand so far was the kettle at 1900w
i realize 3000w at 12 is asking alot, but it gives me headroom for surges.
if i am going to go for a low frequency inverter and smash this one with a sledge hammer, will the transformer in the link i posted, be suitable?
LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408
Posted: 12:19am 26 Jun 2019
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The only way to figure out whether a transformer will work is to look at its datasheet.
If you don't have the datasheet, you will have to recreate the critical parameters from what you have.
No one can tell from a picture of a transformer unless it's a picture of its datasheet whether it meets a certain spec.
I am not sure you realize - when the surge requirement does happen, you are going to lose over 30% of the power in losses, which means you can effectively supply only 70% of the demand you think you are addressing.
You have to have a good idea of what your needs are before you can put together a system that meets your needs.
You don't need an inverter to run your 1900w kettle - all you need is $50 worth of capacitors, $10 worth of components and you are boiling hot water.
No multiple IGBTs/MOSFETs or any of that needed.
How long has this system been running?
It looks like you are invested in this system, so read what tinyt has been recommending, upload detailed pictures in high resolution to imgur, put the links here. if you want to add more details here, you can then downscale those images and upload directly to this forum but I am pretty sure high resolution images on imgur would be helpful.
I look forward to learning more from this thread.
BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961
Posted: 03:46am 26 Jun 2019
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From all the research I've done and I've done a lot
low frequency the only way to go
If I can build one anybody can of course I had some really awesome help
And it was really cheap to build
If you can find a second hand Transformer that weighs around 25 to 30 lb you can build a low- frequency inverter very cheap
Make sure that the Transformer is a type that has a low idle current
Ones out of microwave ovens and most welders will not work idle current is too high
You will want one of the windings of the Transformer to be the voltage that your Mains power that comes into your house is
That way you only have two wind one side of the Transformer the side with the least amount of turns
A troidl Transformer has the lowest idle current but if you can't find one a square One will do
Just make sure that you're able 2 unwind one side of it and Rewind it to the voltage of your inverter board
From what I've read the very most dependable inverter is the warp speed inverter that it takes several Transformers
But if you're looking for something very long term it may be the best way to go
Other people and me have had really good luck with the single Transformer inverter so I am not knocking it in no way
If you know how to solder and can follow directions very closely I think you will be able to build you a inverter very cheaply
as long as you can get the Transformer At a reasonable price
This is just my two cents
I have almost zero knowledge most of the stuff
I just followed the directions of good teachersbe warned i am good parrot but Dumber than a box of rocks
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 08:52am 26 Jun 2019
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ladyn
i havn't invested a huge amount in this system. only the inverter and cabling the solar panels were originally on my garage to run 12v lighting and i was given a few more panels. the wind generator was given to me as non working but i fixed it with a simple bolt. (blade shaft not connected to rotor)
stockleys Regular Member Joined: 21/06/2019 Location: United KingdomPosts: 54
Posted: 08:55am 26 Jun 2019
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the schematic i upoaded was taken from the egs002 manual but i modified the diodes and resistors to match my inverter. the only thing not shown on it are the 2 capacitors by the igbt,s.
please ignore the poor soldering, i need a new tip for my soldering iron due to replacing soo many igbt's
tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 438
Posted: 09:57am 26 Jun 2019
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If the schematic is from fig 2-1 of the egs002 manual, there is a 0.1 ohms resistor (r24). Maybe it is also damaged.
Also, I think there is a mod on the egs002 board that removes the LM393. Maybe it also applies to this inverter.
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