testing the egs002 inverter board

[Phaedrus]

Looks very delicious!
What is the small free standing PCB to the right,in the first picture.

[ClockmanFrance]

Its the OzCooling board.

It has a double independent circuit.

With 2 temp sensors and 2 fan outputs for the Torroid, and 2 temp input and 2 control outputs for the fans for the complete Boards circuit assembly.

[Phaedrus]

Hi Oztules,
Couple of queries again,since I have been reading the thread again :
1)You have attached a toroid in series with the EI core.Is this to limit idle current ? Can you suggest how to make it and how much should be the inductance ?
2)A friend of mine who winds transformers,suggested the use of a split bobbin for inverters.Would you care to comment ?
I should be getting my PCBs in a couple of days,will be having more queries then
TIA
Thomas

[oztules]

Split bobbin is the worst way to wind a inverter transformer. Perfectly good for battery charging, but completely wrong for the inverter duty... don't do it!

Your aim is for the tightest magnetic coupling you can get , not the loosest like a split bobbin design. Tight coupling will be enhanced by keeping the copper in the closest proximity to each winding. Ideally we may split the primary, so half is inside the secondary, and half is outside the secondary, but that would be impractical in this instance if using welding wire for the primary.

If doing a lot in hand for the primary, this could be practical, and would enhance the magnetic coupling..... which is what we want.

The torroid core is just used for lowering the idle current really, but in practice for the real thing I use E65 ferrite with three turns of wire for about 15uh.
That is just a test thing to see the EI running the thing. It is half as efficient idle wise than the torroid, but still acceptable.

So if your winding your own EI, you want the magnetic coupling as tight as you can get it. Your friend will know how to do that. I suspect he thought battery.... and thought charger style would be appropriate, but not so in this case..... we want minimum leakage.....battery charging we want lots and lots of leakage.





.......oztules

[Phaedrus]

Hi Oztules,
Thanks for the clear and unambiguous reply as usual.
Well I just got my PCBs today,and did some prelim testing of the control board.So far the power supply part seems to power up the egs002 board,good.
Also connected a small transformer of 12V to the Vfb connector,just for trials.I adjusted the trimmer till the LCD showed 230V.Used a 5k6 resistor for the high side.Does this sound OK ?
Similarly will try the CT tomorrow by just connecting an external transformer with a load resistor and just the CT.
Am kinda new to power electronics,hence this slow, "creepy" approach .

Thomas

[oztules]

" I adjusted the trimmer till the LCD showed 230V.Used a 5k6 resistor for the high side.Does this sound OK ? "
Not sure at all how you did this without the main transformer attached and the H bridge operational... have no understanding of the LCD operation so cannot comment on what you have seen without more information.

As a guess, a 12v tranny will be about 5k for the  resistor to drive the thing which is odd considering it is not driving the H bridge and transformer, as it is the interaction of the transformer and the pulse width that will determine the pot setting I would have thought.

However, you can trigger the IFB with voltage too, but it is difficult to calculate the result  without real wold testing.

So until you get a h-bridge on the end of it, I dont think you can establish much other than the two feedback loops are active.... which is good at least.


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

[Phaedrus]

Hi Oztules,

Not sure at all how you did this without the main transformer attached and the H bridge operational... have no understanding of the LCD operation so cannot comment on what you have seen without more information.

I just had a small 220V/12V txfer lying around,which is used to inject the 12VAC (after rectification,filtering) into the Vfb pin.Then I adjusted the trimpot till the display showed the same voltage 220V as shown by the multimeter on the primary.I guess all it shows is that the the egs board is reading the input at the feedback.I guess the display is calibrated for a 220V system,and using it with a 110V system,would show a value double of the actual voltage
Similarly , I checked the temperature display by just putting a fixed value resistor in lieu of a 10k thermistor to see if it shows about room temperature,which it did.
Just some checks to see if the things is working,but as you said until there is a HBridge and transformer,its all meaningless.
Thomas

[Phaedrus]

Hi Oztules,
In your reply  Reply #353;

The little caps seemed too big. I know the schematic says 104, but in the end 472 was used or the resistors smoked up on the 23khz sides.

Are you referring to the 4 blue capacitors in the center of the MOSFET board ? Are they high voltage capacitors?They seem quite large.
Also there are two more capacitors (MOVs?),on the edge of the board.Their value is also not clear.I tried enlarging the image,but it gets pixellated.
TIA for your kind support!
Thomas

[oztules]

yes the 4 in the middle.
the "mov" is just a cap.

[ClockmanFrance]

Please See post 152, where the PDF I posted, lists .........

4.7nf Ceramic Disc Capacitor, 250V, 472 (4 off). … CAPACITOR, SAFETY, 10NF, 250V, 20%, (2 off).  ........

Looking at your board, I see that you have put standard resistors near those central 4.7nf Ceramic Disc Capacitor, 250V, 472, .... However, I do recommend, and its silk screen printed on the board, 5r6 or 5.6ohm Resistors 2W Power 5% (4 off).

[Dr_Zogg]

Hi there,
I have a couple of these for the isolation transformer https://au.rs-online.com/web/p/pcb-transformers/1739737/
would you be able to advise me what the appropriate resistor values would be?
thanks heaps for your time.

Cheers,
            Sam

[Dr_Zogg]

also the e-cores that are linked to in this thread from rs components have now been discontinued,
I have found these and should be a suitable replacement https://au.rs-online.com/web/p/transformer-ferrite-cores/6479345/

Cheers,
            Sam

[Dr_Zogg]

also one other thing,
I am making all my boards now and i was wondering if the gerbers for the power board were floating around? (I can't seem to find them anywhere).


Cheers,
           Sam

[Phaedrus]

Hi ClockmanFrance,
Thanks for your input.

Looking at your board, I see that you have put standard resistors near those central 4.7nf Ceramic Disc Capacitor, 250V, 472, .... However, I do recommend, and its silk screen printed on the board, 5r6 or 5.6ohm Resistors 2W Power 5% (4 off).

Actually,that is Oztules board,not mine .

4.7nf Ceramic Disc Capacitor, 250V, 472 (4 off). … CAPACITOR, SAFETY, 10NF, 250V, 20%, (2 off).

The MOSFET board which I actioned,does not have these safety caps at all! I wonder if Oztules removed them for some reason.
As a matter of curiosity,is there any calculation for the values of the RC snubber ?The chinese circuits,dont seem to have any snubbers.
I took a small step forward today,with all the wrong things in place ,viz. split bobbin transformer,4.7nF,100V capacitor and 1/4 W snubber resistor  . Was able to switch on a 100W incandescent bulb,which went without any problem.Tjhe voltage soft starts to 220,and holds steady!
Will load it up more tomorrow and hopefully the holy smoke,will not escape from the FETs , (fingers crossed ).
Thanks much for the kind support!!
Thomas

[oztules]

This is the one I use now. It is 16 fet output.

........oztules