Author Topic: 2000w pure sine wave kit. ebay  (Read 1426 times)

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Offline oztules

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Re: 2000w pure sine wave kit. ebay
« Reply #15 on: January 04, 2017, 07:38:41 PM »
Interesting.... we have no such problem driving phase switching gear here.... heat guns etc.

I guess the 20khz pwm is switching 380v, and so the shaping cap was supposed to damp the 380 peaks and bring it to a sine wave. You have increased that to no avail.... hmmm.

Maybe the scr is a sensitive gate type, and needs some damping between the gate and cathode to muffle the  noise on the inputs.

I use standard emi filters from other gear ( GTI's ) for the filter, and this solves the problem for front loader washing machines..... maybe this is your best bet.

Without the emi filters, the front loaders have trouble not with the normal washing cycles, where it uses the tacho as the speed reference, but the start of the spin cycle, where it measures the current draw of the scr to determine the state of cloths weight against rotation in degrees to see how the load is spread... ie do we spin hard yet, or do we need to mess about and continue to spread the cloths more evenly.
The 6kw selectronic up the hill has that trouble too ( or rather the Asko washer has that problem with the selectronic, but not the power jack conversion)... so that  may help with your musings.

Impressed you have given it a try :).... now fix up the old selectronic next for a spare.

EMI filters should be all over the place, in psu's, and most consumer stuff now.... fridges, dryers, etc etc.


............oztules
Flinders Island...... Australia

Offline rossw

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Re: 2000w pure sine wave kit. ebay
« Reply #16 on: January 04, 2017, 10:23:57 PM »
Interesting.... we have no such problem driving phase switching gear here.... heat guns etc.

I'd expect more problems under the lightest loads - this thing has a motor that draws around 60W.

Quote
I guess the 20khz pwm is switching 380v, and so the shaping cap was supposed to damp the 380 peaks and bring it to a sine wave. You have increased that to no avail.... hmmm.

That was my suspicion too, hence the extra cap.

Quote
Maybe the scr is a sensitive gate type, and needs some damping between the gate and cathode to muffle the  noise on the inputs.

Try a no-gate unit! Damn triac was shorted A1-A2. Have replaced with something out of the junk box, and it's working like a beaut now.


Quote
Impressed you have given it a try :).... now fix up the old selectronic next for a spare.

Hah! It was only your suggestion and supreme confidence that encouraged me :)
The old 5KW unit isn't a contender for this... it weighs 100Kg for a start!
The centrifuge needs to be portable - we carry it around to wherever we're doing our tests, so I wanted something small and light enough to bolt (preferably) inside the centrifuge. This board might just make it, I'll have to make some mounts for it. Otherwise, it'll have to go in a box screwed to the back, or perhaps as a "stand-alone" 110V/60Hz box. I must say though, that I'm sufficiently impressed with the way it works, I might get another one as a spare.


Cheers, and thanks!
R.

Offline oztules

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Re: 2000w pure sine wave kit. ebay
« Reply #17 on: January 04, 2017, 11:25:35 PM »
Chuckle, chuckle.... no I meant fix the selectronic as a back up house inverter using the 8010 chip, or even the egs002 if your a bit slack.... shame to have a 100kg boat anchor, when it could be a super- star inverter again.

It's got a box and transformer... and thats enough to get her going again.


...........oztules
Flinders Island...... Australia

Offline rossw

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Re: 2000w pure sine wave kit. ebay
« Reply #18 on: January 05, 2017, 11:16:45 PM »
Well, it's done and dusted.
The only downside with that board is that it needs not only 380V DC, but *ALSO* 16V AC or at least 14.5V DC, to run the logic.

I have any number of little 5V, 9V or 12V plugpacks, but nothing around 15V. I was testing it all with a 24V/2A plugpack, but that was not going to be very convenient in the devices final application.

So... I grabbed one of the hundred odd 9V plugpacks in my stock. A quick squiz and it has a TL431A driving the feedback opto. This has a reference voltage of 2.5V, and on the PCB it had a 27K resistor to +V and a 9K7 to Gnd. Didn't take long to figure out that replacing the 9K7 with a 5K6 and I'd have a nice 14.5V - and it worked great.

Ripped the board out, mounted it on the inverter board, bypassed the current limiting on the mains side, stole the SMPS bridge to drive the inverter... and we're done!





Put it all back together and it runs smooth, quiet and cool. Oh, and at full speed!
Thanks everyone for your contributions and encouragement!

Offline MadScientist267

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Re: 2000w pure sine wave kit. ebay
« Reply #19 on: January 06, 2017, 07:51:24 AM »
Nice implement Ross, indeed.

Now that I've had a chance to look this over closer, only one additional thing comes to mind for the "filter" question for smoothing...

The output filtration may be better looked at in terms of a "freewheeling buck converter" of sorts... there's LC action yes, but you (or anyone running across this at a later time) might find the answer to the choppy vs smoother output amongst the "continuous vs discontinuous" inductor operation associated with buck and boost converters.

In a sense, that's essentially what's taking place. When the load is sufficiently mismatched, not enough (or too much) current flows in the inductor at the output, leading to either something resembling discontinuous mode in a converter (which as you found, the cap only plays a "niche" role in), or in the case of more current than the ideal, saturation, leading to ripple caused by the core going non-linear. Tinkering with the value of the inductor will have a much more profound effect on the "quality" of the output (which of course in the case of your motor drive or other "dedicated load", can be dialed right on in.)

This isn't to say ignore the cap, it just doesn't play the role that it immediately might seem to play in the big picture.

On a related note, if you look at the front end of an active PFC circuit for switching supplies, you will spot the immediate resemblance to the final components in a PWM/PSW inverter filter... the only real difference, is (nearly literally), everything is completely reversed. The mylar cap plays a key role there just as in the inverter, and is appropriately referred to in many cases as the "resonant cap" - bigger or smaller upsets the balance of the LC and the inductor needs to be adjusted as well to suit.

Only other thing, which I'm sure goes without saying, but maybe not so much for those just starting to get their feet wet in this stuff, is of course all of this is very heavily intertwined with the base switching frequency for the PWM that ultimately creates the sine...

Ain't SMPS so much more fun than boring old iron laminate EI, a simple bridge, and electrolytics that easily found new life simply as paperweights?  Or "Power Hartley's" that make better heaters than inversion circuitry?  ;D 8)

Cool stuff.
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Offline rossw

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Re: 2000w pure sine wave kit. ebay
« Reply #20 on: January 06, 2017, 01:42:28 PM »
Thanks Steve.
It's really not as bad output as my earlier post implied. When I first fired it up, I hooked my DSO on (but as it's mains operated and almost certainly grounded, and since the inverter is full-wave rectified mains, I figured it wasn't a bright idea to just clip the CRO straight on the output!).

Here is the output, with the physically smallest transformer I could find - ie, the least iron and windings to filter out the crud.


(Ignore the voltage, it's not representative of anything, the waveform alone, and it's frequency, is all that this pic was to show)

The failed Triac was (as I have now determined) as result of the failure of the autotransformer in the penultimate "work-around" (trying to give the motor only 110V from a 240V supply, and the point I gave up with such folly).

Offline oztules

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Re: 2000w pure sine wave kit. ebay
« Reply #21 on: January 07, 2017, 01:41:33 AM »
Steve
 "This isn't to say ignore the cap, it just doesn't play the role that it immediately might seem to play in the big picture."

No..... the cap in question Ross fiddled with does not work as you think. It is the shaping capacitor, and without it, the wave is unrecognizable, and the VFB won't even work, and will swing to PWM max.. and then die.  It cannot work with out it.

The noise filtering is not critical, and anything will work to some extent.


..............oztules
Flinders Island...... Australia

Offline MadScientist267

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Re: 2000w pure sine wave kit. ebay
« Reply #22 on: January 07, 2017, 04:36:48 PM »
Oz -

Oh, no I agree it must be present. Shaping, resonant, similar of not outright identical concepts behind the names.

What I was mostly getting at is it only has so much effect because it needs to be within a relatively narrow window of values to do it's job correctly.

The inductor has more room for playing with the value because it's catching and converting the PWM, with the cap being part B of that conversion (representing the low impedance that the inductor needs to do /it's/ job correctly.

This was why I pointed to the inductor as the more flexible component in terms of making changes. The cap has 2 jobs to do, "terminating" the inductor, and shaping the sine. If it's too big, distortions from excessive energy storage... too small, sine gets spikey because it isn't able to hold on long enough between pulses. All the inductor has to do is dv/dt control by virtue of ELI, hence the "buck converter" reference, into the cap where ICE finishes the job. 

They're both critical components, just one has a bit more wiggle room for tweaking than the other for a dedicated supply such as the centrifuge.

That said, if that's the wave you've got Ross, I'm not seeing anything to bother with any tweaking ;)
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Offline boB

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Re: 2000w pure sine wave kit. ebay
« Reply #23 on: January 09, 2017, 09:43:02 PM »

Happy 2017 kids !

At Trace Engineering in the late 1990s, one of the engineers (Milt Rice RIP)  was working on
a product called the "Co Sine"  that was basically one of these deals that took the rectified
output of a modified-square wave inverter and turned it into a sine-wave add on.

"ALMOST" became a product but it cost too much back then.

boB

Offline Fionn

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Re: 2000w pure sine wave kit. ebay
« Reply #24 on: January 12, 2017, 07:14:54 AM »
Are you rectifiying the mains input before the board or is there any need?

Offline rossw

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Re: 2000w pure sine wave kit. ebay
« Reply #25 on: January 12, 2017, 01:34:09 PM »
Yes, I have full-wave rectification of the mains before the board, and yes it is necessary!

Offline Fionn

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Re: 2000w pure sine wave kit. ebay
« Reply #26 on: January 16, 2017, 06:14:00 AM »
Thanks, wasn't sure if it was included on the board or not.
Any idea if there is any headroom available above the 380V level?
If it could run up to say 400V, it could be an option for running AC loads direct from the battery pack of a Nissan Leaf for example, could be useful!

Offline rossw

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Re: 2000w pure sine wave kit. ebay
« Reply #27 on: February 27, 2017, 10:59:19 PM »
OK, Oztules (particularly) - but anyone else with any bright ideas, I'm looking for guidance!

After the great success of my previous centrifuge conversion with one of the you-beaut HVDC input pure sine inverters, I thought I'd do the other one. Ordered the same inverter kit from the same guy....

... only it turned up different (of course! Why wouldn't it?)

So I assembled it anyway, it has an extra output filter, slightly different input requirements (has 15V reg rather than 12V) but otherwise superficially looks the same.


The only perhaps "notable" omission is that it only has a single 2.2uF/630V cap in the primary filter.
The output - measured through an isolating transformer (which should clean it up a bit) looks bloody horrible:


The "flat-spotting" is not crushing from insufficient DC - if I adjust the voltage set pot, the waveform retains the same shape, while the output voltage goes up and up and up... (it's backed off to 110V here, but it keeps that waveform the same if I take it up to 180 or 200V - so it's intrinsic)

The output also has all manner of spikes and spurious, the frequency drifts all over the place. 60Hz +/- 1Hz.

Since it's driving a computerised phase-control speed controller, the results are... well, it's unusable.

I don't expect any sort of help from the vendor - there's absolutely no controls other than the voltage adjust, I'm at something of a loss where to look at. Ideas??

Offline oztules

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Re: 2000w pure sine wave kit. ebay
« Reply #28 on: February 28, 2017, 02:55:55 PM »
There may be a few ways to kill a wave like that... but the changing HZ and the glitchiness would suggest a lousy board... perhaps get another egs002 for  ten dollars and try that. ( or steal the one from the working board you have already) The fet board should not cause that.... more likely from the driver chips being "loose" or an earthing problem on the 002 board....

In short another 002 should solve it I would expect...... or you could try to find out if the caps around the 2110's are secure, as it looks like the driver gives up at some point.


..........oztules
Flinders Island...... Australia