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Very interesting concept. Ive not seen it before.
Hello LM thank you for your reply, me too :) I came across it some years ago drawn by a guy looking for help with a Chinese GTI that kept blowing Mosfets, at first I thought he had drawn it wrong but apart from changing a few diodes to zeners it seems to work perfectly except.... said problem of unreliability. His GTI was a simple 12/24V 300W plug in the wall type.  I just wondered if anybody had encountered a circuit like this in big multi-kw grid tie's.

I should mention that what the drawer labelled as +/-360V is actually the output from a high frequency pwm and is in fact a 100hZ unipolar sinewave. This circuit (H bridge) is sometimes called an inverse rectifier, sometimes an unfolder and I am sure has several other names too, I have also seen thyristor implementations.

At the moment my GTI unfolder is as I say a traditional hard switched H bridge using timing derived from the microprocessor that ultimately is derived from the grid zero cross however I have lost a mosfet in unexplained circumstances so if that happens to often I may try this one except I dont have a pcb for it at the moment and its hard to do high voltage stuff on breadboards.

Anybody out there torn down there GTI to know what the active circuit is immediately before the grid connection ?
Automation, Controls, Inverters, MPPT, etc / Re: 3 Phase inverter EG8030 EGS031
« Last post by Mulver on April 27, 2017, 06:17:56 AM »
Hey Roberto, Any update on your load tests?

Cheers Shane
Interesting ...but still pretty complicated. Nice to see it made into modules though  ;wonder what the CPU is?
Thought I'd have a scan of the latest prices of spare controller & power boards for the PJ and found this ALL NEW  product development

Can't see any 48v or 15kw power boards though.

Steve / Re: My Scratch Pad
« Last post by MadScientist267 on April 26, 2017, 05:09:53 PM »
There will always be some earth current, unless you're floating in mid air, it might be micro amps but there will be some path to earth if the system is earth referenced.

The example you give is not really relevant to the safety of a standard electrical installation whatsoever in any case. You have created an insulated matting and adapted your behaviour to avoid creating earth paths by your own admission - hardly typical of the usage of standard electrical appliances.

Regardless, this is a moot discussion, I clearly stated in my post that protection would only be provided if the fault current exceeded 30mA.
We're in agreement so I don't see what we're adding to the discussion at this point.

Or are you in fact arguing in agreement with the OP that we should do away with earth referencing and RCD protection and go with unmonitored floating installations?
Hang on, scratch that Ross, I fully qualified in my original post that the fault current would have to exceed 30mA - directly under the line you quoted.

And I contend that there are plenty of times when standing, working on something where there would NOT be any earth current if you got tangled up across active/neutral and that therefore the RCD would NOT operate.

My workshop floor for example, has large rubber mats - mainly to reduce foot and leg fatigue.
Over my many years working on stuff, I tend NOT to lean against or otherwise contact the metalwork of equipment, switchboard frames, equipment enclosures etc.
So tell me where the earth current would come from when I've got the covers off a "thing" and get myself across Active and Neutral??
Hang on, scratch that Ross, I fully qualified in my original post that the fault current would have to exceed 30mA - directly under the line you quoted.
I agree wholeheartedly Ross, the fault current to earth would still have to exceed 30mA of course, I was merely trying to illustrate that the standard approach at least has a chance of working in that fault scenario. Some current will certainly flow to earth however so I don't think "may" is appropriate, the only uncertainty is around the quantity.
An unmonitored distributed isolated system has a far greater chance of causing unintended death however.
This thread is rife with practices that should never be followed.
Very interesting concept. Ive not seen it before. At first I misunderstood the term "unfolder"  This circuit is then only used for the timing synchronizer? Seems like it should work for that but the proof be in the actual performance. Be best to build it on breadboard and watch how it behaves with scope. 

If this is your complete circuit and not just a timing reference then i would say not a good idea. It only switches once per half cycle which would produce much distortion (any energy that falls outside or inside of the sine curve). Most grid tie inverters switch many times per half cycle dumping their power into an electrical flywheel (inductor) which outputs a true sine curve matching the original plus some current flow. Impossible to do this with only one switch per half cycle unless you used a class c amp with inductor and capacitor tank circuit tuned to 50/60hz, be tough to deliver any appreciable power though. From what Ive read H bridge is only way to go above a few hundred watts.  Anyway, have fun with it!

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