Another PJ

[frackers]

Nearly finished the OZInverter project but rather than revive a thread that is over a year old, I'll continue here.
Here are pointers to the original item I posted.

The project started with the breaking down of a 5 current transformers. Originally (I think) from 11kV line equipment, they were very old (Imperial sizes) and found in an old oil drum in a scrap yard half submerged in water.

http://www.anotherpower.com/board/index.php/topic,1066.msg10588.html#msg10588

The toroids were rewound

http://www.anotherpower.com/board/index.php/topic,1066.msg10591.html#msg10591
http://www.anotherpower.com/board/index.php/topic,1066.msg10601.html#msg10601

and that is as far as I'd got when I last posted about this project.

[frackers]

The next part was assembling the (now 5) sections into a single huge (25kg) toroid. This was done with polyurethane glue, and since that requires water to make it 'go off', a contribution from the wifes sewing room with some polyester interfacing (as used in collars etc) to go between sections.



The polyester was cut to the same size as the core sections



and each one was dampened, glue spread on the two faces of the cores and it all clamped together in a stack



Next came the cable for the primary. My mate Andy, champion scrounger par excellence, has scored again!! First with the cores, then the 1.8mm coppper wire for the secondary and now with 13 m of 50 sq mm flexible welding cable for the primary. That's enough for mine and Andy's transformers which will require about 5.5m for the winding so leaves a bit for the tails!

Its double insulated (14.5 mm diameter) so the outer orange PVC will be removed (inner is 11.5 mm) to get the 12 turns into the toroid.

[frackers]

First job was to get a layer of mylar on the core

I used some corner pieces to radius the edges (thin irrigation pipe) and set to.



When it came to epoxying the first winding layer, disaster!! The irrigation pipe corner 'protectors' held the wire out from the core surface and prevented the whole thing holding together. I wasn't very happy with the winding itself either!!



The result of this was stripping it back to bare metal and starting again having rounded the corners off with a flap wheel

Anyone attempting a rewind might be interested in my 'patented bicycle wheel winder' !! You can see it in action on youtube - first with the mylar

https://youtu.be/RbuXQ005wE8

and struggling with the 1.8mm wire

https://youtu.be/kYtudDVucUo

Having 3 secondary layers onto the core, it was time to check that I had the same number of turns on each one. This is the result of the difference between the first 2 windings with one energised with a 100w bulb in series as a current limiter.

[frackers]

Time to put all the bit together on the bench and see if it flies.

Using a 1kw telecom PSU to drive it (my battery bank is set up for 24v at present) I loaded up to the maximum that the PSU can deliver with just over a 1kw. Very happy with this as the heat sinks are only just warm enough to see they are above ambient temperature.



31kg and the monster is complete. More irrigation piipe, some MD40, to space the primary round the hole!!



And that is as far as I got by April 2016 when life (visit to the UK, winter, work etc) put a hold on things for a while.

[frackers]

Summer is here, Christmas holidays so time to put the inverter into a box.

Another trip to the scrap yard for Andy resulted in this  fibreglass electrical panel enclosure



To carry the weight of the core and hold everything else into place I made a steel subframe.



This fits onto studs cast into the enclosure and has mounting holds for a wooden panel that holds the main electronics and 10mm nuts welded to the underside to take the toroid mounting bolts.



Y.M.I.P (Yet More Irrigation Pipe) as spacers for the toroid mounting bolts, exterior plywood to hold but not crush. A pair of Papsp Variofan thermostatically controlled fans, scrapyard again, ex-server rack cooling shelf!

[frackers]

I bought a proper E core after messing about with ferrite C cores and managed to get 4 turns through it so happy with that!!



And finally (so far) MCB and RCB and a couple of sockets (for local use only!!) on the door of the enclosure.



No monitoring yet, I'm working on a variation of my wind turbine controller to start with, that will only monitor the DC side of the inverter so I'll be re-writing it from an AVR to an STM32 and getting use of all that loverly DMA, 14 bit ADC, USB, super fast FSCM ((flexible static memory controller) for a TFT display and all that good stuff.

[bj]

As always Frackers, a very nice build.

[oztules]

Nice when a plan comes together 

You have done this hard Frackers, no-one else has  really built a transformer from scratch scratch... well done

I now pull the centers out to 100mm and add that to the outsides, but thats a long way from a total coil rewind.



.........oztules