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Tinker
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Posted: 11 February 2017 at 10:19am | IP Logged Quote Tinker

Warpspeed wrote:
Grogster,
The positive connection running across the top, (between the two drains) was elevated by placing steel spacers between the mosfet drain connections and the aluminium strip to clear the gate connection of the upper left mosfet.


May I suggest not to use steel spacers for what is a high current connection.
I'm doing the connections in a similar way but with copper spacers (turned from copper rod) but aluminium spacers would also be better than steel.

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Posted: 11 February 2017 at 9:13pm | IP Logged Quote Warpspeed

Yes quite right, I was planning to do something a bit better later on for those spacers. At the time it was only a preliminary mechanical mock up. I have a lathe here so that type of thing is easy, but I lacked any better material at the time.

The long 5mm bolt that goes up through the Hall sensor is surrounded by some 3/8 copper pipe that is a nice snug press fit through the hole in the Hall sensor.

Its funny though, you see TO220 packaged mosfets with those skinny legs rated to carry 100 amps or more in the data. But people (myself included) look at a 5mm or 6mm steel bolt and wonder how much current it can carry.





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Posted: 11 February 2017 at 10:03pm | IP Logged Quote Madness

There are lots of copper and brass bolts, washers etc on Ali express for very little money if you are pedantic about the resistance.

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Posted: 18 February 2017 at 9:37pm | IP Logged Quote oztules

Been pondering this for a bit, and had a chance discussion with Gordon ( from here ).
He has had a lot to do with this stuff during his time in the solar challenges ( last century)

He feels that the inductor we use is simply a choke for the frequency I didn't design it for. It has nothing to do with the fundamental frequency we are switching at, but rather chokes off the excessive currents in the first few nano seconds of the steep rise time of the switching. This is probably more in the order of 100 mhz, not the 20khz we switch. This makes sense to me, as the inductance is so tiny to make such a huge difference.... now I see why. It explains the heat in the inductor as well.... that hf frequency energy has to be dissipated.



Thats the first thing.

Next... drive problems.
He agrees the cross over or near cross over glitches cold be caused from drive or lack thereof. A simple solution may be to use a bigger cap on the 12v supply side of the high side switch driver. It could be that we are drooping on the drive voltage to the chip... so maybe use a 47uf instead of the 10uf.... and a ceramic one or tantalum perhaps. The bypass caps need to be as close as possible to the vcc and gnd of the input side as well. ( mine is already).

Failing that then a totem like Madness is doing will probably solve it.


...........oztules



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Posted: 18 February 2017 at 11:25pm | IP Logged Quote Madness

oztules wrote:
Mad,
Further testing with the inductor gives me a huge range of weird stuff.

It looks like the noise in my transformer is induced by the inductor.
By changing the inductor form iron powder to ferrite, from ecore to ring and changing the turns.. the noise and waveform imperfections changed radically.

On one setting with the ring and 10 turns the tranny was so quite I had to put my ear next to it to see if it was running. With a different ring and 10 turns, the wave from looked like your trace at idle, and sounded like a chaff cutter at idle, but straightened up a lot when loaded.

So it looks like that with removing the 4u7 and fiddling with the inductor, we can change the waveform markedly. It may be I am on the edge of decency with regards to drive, but gee, it gets very good by fiddling the inductor, and removing the 4u7 on the VFB line.

more to follow as I find out more.... gee it would be nice if I knew what I was doing too


...........oztules


Hi Oz,

I tried changing the Zener diode to 18 volts on the supply to the IR2110 chips, it made no difference to the wave however with the board just idling while I went over it with the CRO it got very hot. I went to put a clip on the output and nearly burnt my finger, it was up to 85 degrees with no load. It was drawing 4 amps with zero load.

I have gone over the PCB I am using ATM and resoldered everything then I back tracked on what I have done and remembered how I got a better result with no choke. I tried that again this morning with a standard EGS002 control board with 4u7 removed and a full house of HY4008's, no choke and the waveform is perfect. Put the Ecore choke in and it has wobbles and blips, it improves with load but still looks like previous results in the image below, however this is with the default EGS002 dead time, the image is from a different Power PCB and maximum dead time.



Have you got more details Oz of the choke you mentioned in the post quoted above that worked so well?

Edited by Madness on 20 February 2017 at 12:10pm


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Posted: 20 February 2017 at 12:10pm | IP Logged Quote Madness

Just been trying a few things with the Inverter, setup is eg8010 board with 4.7uf Monolithic caps added to the 10uf electrolytic on the 12V side of the IR2110, single core Toroid and no load.

1 turn through Ferrite Ring




2 turns through Ferrite Ring




3 turns through Ferrite Ring




4 turns through Ferrite Ring




5 turns through Ferrite Ring




3 turns through E-Core




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Posted: 20 February 2017 at 2:15pm | IP Logged Quote Tinker

Yes but, also measure the no load current.

The whole idea of the E-core or ferrite ring was to reduce this idling current.
Remember, this current draw happens 24/7. So, unless your battery bank can afford to just laugh at this idling current...

Somewhere its going to be a compromise I guess, juggling the lowest idling current with an acceptable sine wave.

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Posted: 20 February 2017 at 9:22pm | IP Logged Quote Madness

Until I get the waveform correct I am going to keep blowing MOSFETs, there is no compromise on this. I did measure current while doing this and with one turn it was 2A at best just a touch over 1A. With the single turn and no load there was noticeable heating in the Ferrite ring.

Something is amiss I just realised those images are upside down so should be like this.






I will try a different MOSFET board later and see if there is any change as a result of that.

Edited by Madness on 20 February 2017 at 9:24pm


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Posted: 21 February 2017 at 12:28am | IP Logged Quote oztules

Saw the unit running at 6kw or more, so thought a few pics...

over 6kw driving hot water, front loader, electric jug freezers, tv, etc etc.




Interesting wave form showing a glitch... blown up as big as I can make it...




and it turns out that the glitch was caused by the phase triggering of the front load washing machine motor... each time it rotated slowly for the wash, it got the glitch, then a few second later... would stop, and reverse direction.... whilst stopped, it looks like this.... ( still pulling near 6kw with motor stopped )



So now we know that phase triggered appliances using fair power, will distort the wave form... but not too much... especially when pulling 6kw or more.

I do like these 8010 things.
This one has done half a mega watt, but was only idling for a week or so while I was testing another.

The original power jack unit in the hydro box was a few years old, and gave up while only doing a few watts a couple of days ago..... I think it was to do with sensitive under side of the board stuff.... It would not switch on if left for a few days over here ( very humid island at night ), and would need a hair dryer to start it up... should never have turned that one off for extended periods whilst testing other units in it's place. Have heard of other powr jacks doing the same thing if youleave the tape they stuck on the back ( i did).


........oztules

Edit.... went and had another look after some of the loads went away, and the wave looks identical to the bottom one at 2.2kw, 3.5kw, 4.5kw, and 6.1kw. It was only the phase triggering of the triac control in the washer that made any difference at all. Voltage remained within a volt at all times. ( I run around the 233v mark)




Edited by oztules on 21 February 2017 at 12:56am


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