Anotherpower.com Forum
Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: ClockmanFrance on January 05, 2016, 02:33:08 am
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Making a Big OzInverter
Hi,
I am putting together my No 2, Big OzInverter.
I have a couple of questions about the toroid.
Yes, I have read most of all ‘oztules’ 60,000 words of wisdom, he has gratefully posted on 3 forums. I thought that I had understood the toroid concepts. But sadly my head is still spinning a bit.!
My No 1, 6kW OzInverter, 48vdc to 230vac 50HZ, works fine and does everything I wanted. ........The cores were 2off 190mm outside diameter x 90mm centre hole and each core was 60mm high. These were stacked together, so the rectangle section through the core was 50mm x 120mm high. 4off /4 in hand, 1.8mm diameter at 118 turns Secondary, and 50mm/2, 14 turns, Primary.
My No 2, OzInverter, will be for the final installations here in Normandy, and will incorporate a better metering system. The cores will be 130mm outside diameter, 100mm diameter centre hole and each at 70mm high, stacked together that gives me a rectangle section of the core 65mm x 140mm high. That’s just over 30% more core mass.
Question, ….. Does this 30% more mass mean a proportional increase in the secondary windings, ie, should the 4off/4 in hand 1.8mm diameter, now be 158 turns. Or can I get away with less turns and save copper losses?
Or is the extra copper/turns, only proportional to the outside diameter increase and not the height, so the increase of turns would be about 20% in this case.
Question, ….. I am using 75mm/2 for the Primary, again is there a proportional rise in the number of turns to say 18 turns. ?
Thank you.
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Lemme see...... I make that as about 9100mmsq cross section... so ... and here I can only go rule of thumb....9000/2800=3.25
So I figure about 3.25 volts per turn.
So the secondary will be about 73 turns, and the primary will be about 9 turns.
How that would be worked out mathematically I can only postulate, but the in the real world measurements I have done, it would seem to indicate that roughly 2800mmsq of cross section at 50hz will yield about 1turn/volt.... so 9000mmsq would be about 3.25 volts/turn.
If we wind for a few more volts than we want, our saturation is further away... so say 240 or 260v for a 220v system gives us leeway and lower magnetising current ... from there about 1:8 primary : secondary.. and we have a workable start point.... at least that how I would tackle it.
Provide you have a crane close handy to hold the thing for you, it will be easy to wind.. big hole and plenty of room. It will be important to map out the wire sectors in advance.. or it will all end upon one side :)
Your core manufacturer will be able to give you exact figures I suspect.
.............oztules
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Many thanks oztules.
Crikey I was going 100% the wrong way, I was adding turns/copper when I should have been subtracting.
Good job oztules is guiding me along.
"If we wind for a few more volts than we want, our saturation is further away... so say 240 or 260v for a 220v system gives us leeway and lower magnetising current ... from there about 1:8 primary : secondary.. and we have a workable start point.... at least that how I would tackle it."
Thanks,.... I will go for 80 turns on the secondary and 10 on the primary and see what I get when I test the secondary.
"Provide you have a crane close handy to hold the thing for you, it will be easy to wind.. big hole and plenty of room. It will be important to map out the wire sectors in advance.. or it will all end upon one side :)"
My last set of cores were 20kgs, this new set will be 35kgs, so I will do a soft pad that the toroid can sit on that is on the cut out bench, while I wind, and lift/rotate about 6 times each winding.
Yes, I will do some templates and see how the spacing of the secondary works out, I might even add another so I have 5off/5 in hand, off 80 turns at 1.8mm diameter, depends on how the wires lay.
I am looking forward to this build...........
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Hmmm - this is getting interesting!!
Based on the 2800sqmm for 1V/turn and on the 1st layer being next to the core, and the cores I've made (210 outside, 90 inside, 25.4 thick) then:
4 of my cores would require 111 turns for a total of 22.5m of wire per layer, 14 turn primary
5 of the cores would require 89 turns for a total of 22.5m of wire per layer, 11 turn primary
I think this pushes me to the 5 core solution as it doesn't increase the copper loss, it improves the cooling ('cause its bigger!!) and makes more room in the centre for thicker primary due to less turns.
No excuses now - I have 1kg rolls of 3 thou and 5 thou mylar and only 1 more core to make (I'm making 10, 5 for me, 5 for a mate).
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Based on the 2800sqmm for 1V/turn and on the 1st layer being next to the core, and the cores I've made (210 outside, 90 inside, 25.4 thick) then:
4 of my cores would require 111 turns for a total of 22.5m of wire per layer, 14 turn primary
5 of the cores would require 89 turns for a total of 22.5m of wire per layer, 11 turn primary
I think this pushes me to the 5 core solution as it doesn't increase the copper loss, it improves the cooling ('cause its bigger!!) and makes more room in the centre for thicker primary due to less turns.
Well, I've made a 5 core toroid, it has come in at 25kg so there is certainly some metal in it! Could someone check my calculations as I just came up with different answers to those above!
Core size 210mm outside(O), 90mm inside(I), 127mm high(H).
Single turn is H*2 + (O-I) = 374mm
Cross section is ((O-I)/2) * H = 7620sqmm
so using 2800sqmm per volt and aiming for 240v secondary and 30v primary
Secondary Turns = 2800/7620*240 = 89 turns - maybe use 90?
Primary Turns = 2800/7620*30 = 11 turns - maybe use 12?
One layer of the secondary is = 374* 89 = 33.3M (again rounded up).
I have 12kg of 1.8mm wire so based on the density of copper being 8930 kg per m3, I have a total of 12000/(.9^2*pi*8.93) = 528m
Possible layers = 528 / 33.3 = 15.9 (i.e. will do 15 full ones). I was planning on 4 so I have enough wire!!
The last couple of weeks has been making sure the cores are flat, sealing them with exterior polyurethane varnish then stacking them with polyester material (raided from the wife sewing room - wadding that compresses down to 0.2mm) that allowed me to get some moisture into the joints made with Durabond Aquadhere polyurethane glue. I chose polyurethane as its good for up to 140C and if I made a mistake they will split down again unlike epoxy.
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Yes I figure about 2.7v/turn
So 90 turns and 12 will work, or even a few more to get the magnetising current down, as you have a heap of steel there to coerce into action.
I would probably go for 96:12.
...............oztules
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Just started on the first layer of mylar tape but I think I should have something to cover the 'sharp' edges of the toroid - it looks like some sort of fibreglass strip in http://www.anotherpower.com/board/index.php/topic,1044.msg10166.html#msg10166 (http://www.anotherpower.com/board/index.php/topic,1044.msg10166.html#msg10166) but since I've started from cores that used cardboard, what would be a suitable alternative?
Some sort of thin plastic right angle extrusion with a rounded outside edge would work for the outer faces but not quite sure what would work for the hole in the middle!
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Glass matt is what they use... but I guess cotton will work just as well with some sort of binder ( polyester fiber glass , epoxy etc).
Anything just to make the wire not able to be bruised and exposed to the core... ie provide some solid radius to the edges.
...............oztules
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I'm tempted to just run an angle grinder round it to take off the edge - maybe use a mounted stone for the inner edge. I'll try that on a spare core and see how it comes out.
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I'm tempted to just run an angle grinder round it to take off the edge - maybe use a mounted stone for the inner edge. I'll try that on a spare core and see how it comes out.
Tried it on a spare core and not very good - the material is quite soft and I don't have a fine grinding wheel so rather too tatty round the edges!!
I did succeed with some fine irrigate pipe (what I call spaghetti pipe) split down the middle and held in place with tape until the first layer of mylar went on to hold it permanently. Looks pretty good!
Not having taken a toroid apart, I've no idea how many layers of mylar I should be using. I'm using 5 thou for this first core insulation layer and then I'll move over to 3 thou for the inter-winding layer separation. I'm doing a 50% overlap so I have a double thickness of mylar but no idea if that is all that is required :(
Can someone who has stripped a toroid give me a clue or 3? Progress so far can be seen here (weekends are not good for uploading pix!) http://gilks.ath.cx/gallery3/index.php/Building-a-PJ-inverter (http://gilks.ath.cx/gallery3/index.php/Building-a-PJ-inverter)
Cheers
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I use this on the edges.
80 grit flap wheel.
It works well and leaves a smooth small radius, with no roughness, so the copper wire forms a neat non stressed corner.
From the book....
" I normally use 0.055mm, or 50 micron thick mylar tape its just right.
I half lap the Mylar tape on its self on the exterior of the toroid, and I do 2off complete wraps as a minimum, with the super thin breaking stuff I have salvaged I did 3off wraps, Waste not.
Don't forget the epoxy resin on each secondary winding before you cover it with Mylar tape. I like the thin viscosity stuff that I mix and lightly paint on.
I have some thin Molinex sheet that I put under the whole toroid to collect any excess resin.
The following evening turn the toroid over, peel off the Molinex sheet, Mylar tape on the hardened, but still soft, epoxy resin coated winding, and then next copper wire winding goes on.
I use a small length of mylar adhesive tape here its yellow colour, to hold the mylar wrapping tape in position.
I get some mylar from the USA...... http://www.ebay.co.uk/itm/181696004499?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
..... its 0.125mm thick, 120micron, but i found that it is just too thick. Especially when its not flexible enough to allow the next winding of the secondary to fit down in the gap of the previous winding, especially on the internal centre hole windings. But it does come oval shape and goes down a 62mm dia hole okay without having to unwind. And it is ideal for the last winding before the Primary goes on."
Trust this helps 'frackers.'
Toroid first wrap with 50 micron, that's 2 layers thick.
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Frackers, I like what you have done thus far.... 2 layers as Clockman says is what I have done also.
.................oztules
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Frackers, I like what you have done thus far.
Thanks John
Shopping for paintable epoxy tomorrow so I can finish off the first secondary layer. More pix in the gallery on my website.
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(yet) Another question - does the fan on the 48v units run at 48v or 12v? My mate Andy who has scrounged up nearly all the bits for this build managed a few rack shelves full of 48v 115mm Papst 5w fans with tacho outputs :)
Assuming the fan runs at input volts I can put one on the control board and put the other 2 I have (more available!!) on whatever Atmel/STM micro I use to monitor the system with. Perhaps PWM them to keep the noise down if full wack is not required!
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On the cheap 48v PowerJack 10000 inverter I purchased, the two 120mm fans were 24v in series with their own heat sensors. The PJ safety fan was 12v. Their is a socket on the control board that gives 12v and it runs my 'OzCooling' circuit with 2 off 12v 120mm fans.
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PJ safety fan connections.....
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The PJ safety fan was 12v. Their is a socket on the control board that gives 12v and it runs my 'OzCooling' circuit with 2 off 12v 120mm fans.
Thanks for that - I'll look for a PC chassis fan...
Just been putting the epoxy onto the first winding layer - what a disaster! I'll know next time to just do the top (i.e. mix up not very much!!) and when its gone off turn over and do the other end.
I had to scrap the half hardened resin off where it had formed a rim round the base that was sitting on a plastic sheet. I'm using R180 resin (if that means anything to anyone) which has the constancy of water after its mixed with the hardener. At least I sensibly choose the slow harder so I had time to rectify most of my mistake of just a bit too much resin.
Problem now is that it is so thin a resin that it hasn't really stuck anything to anything else :-\ Not sure if I'll bother with the next 3 layers.
To add insult to injury, when I was trying to recover things one glove got a hole in it so I had resin all over my fingers and I was busting to go to the loo!!
Sticky moments :o
I think I'll sit and look at it for a day or two and may very well strip it and start again...
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With most resins you can use chalk powder as a thickener, mix it well with the epoxy first before adding the hardener.
Try a little test batch with a little epoxy and see how you get on, chalk also slows down the hardening process.
Quantity of epoxy I used each secondary was about 20 to 25ml.
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Having found a crossed over wire, I'm going to strip back to bare metal and try the flap wheel to radius the edges. The gluing problem is mostly down to the corners being raised by the half-round of thin pipe I used to protect the wire from the edges and hence lifting the wire from the core.
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Done!!
60 grit flap wheel (which I found in the toolbox) certainly did the job of rounding off the corners and I have the first layer of mylar on it.
Hopefully tomorrow night I'll get back to where I was - but better ;)
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It has taken nearly a week but the first layer is now on and the "colloidal silicate adhesive filler" mixed into the epoxy has done a great job locking it all together (well one end anyway - got to turn it over and complete it tonight!!)
Question - is it recommended that the layers all start and stop at the same place or should there be a bit of offset to allow the tails to emerge from the bottom layer(s). Not looked at any photos closely enough to see but not sure it would be obvious even if I did!!
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i use same place...
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I start each time at the top.
Right angle then adhesive mylar tape the copper, then its up and over and down the hole.
I finish each time at the bottom, then more adhesive tape.
You can see the epoxy in the photo, but this is the second to last secondary, the 3rd.
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The Big....
Just the cores is 35kgs.
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Thought it might be interesting to demonstrate my bicycle rim toroid winding technique. The clip starts off with showing the size of the rim (400mm).
Note the red tape marker so I can count how many turns of material I load onto the rim. The mylar needs 22 turns and the wire (for 96 turns on the toroid) is 36 turns.
The winding of wire I'll capture later in the week - basically the same but a bit of tape to stop all the wire falling off the rim.
https://www.youtube.com/watch?v=RbuXQ005wE8 (https://www.youtube.com/watch?v=RbuXQ005wE8)
Enjoy :)
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Now that is absolutely brilliant.
Thanks for the share
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Now that is absolutely brilliant.
Thanks for the share
Thanks for the complement bj
This next clip is the rather messy wire winding - the result is OK and it means no joins in the winding but it is time consuming and takes a fair bit of work to get a tidy result.
https://www.youtube.com/watch?v=kYtudDVucUo (https://www.youtube.com/watch?v=kYtudDVucUo)
It has worked 3 times as that is how many layers I have now!
I was hoping to get a fourth layer on but a trial run with the primary makes me think it won't fit. It weighs in at 31kg now so assuming the mylar and epoxy doesn't amount to much that is at least 5kg of copper on it.
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4070.JPG?m=1456635984)
Does the primary need to be all nice and tidy or is it just a matter of getting the wire through the hole? The 3 secondaries are 1.8 mm diameter wire (2.5 sq mm cross section), is that likely to be OK up to 6kw (25amps) or would I be pushing my luck ;)
I have removed the outer (orange) insulation layer from the 50 sq mm welding cable and if I can find some heat shrink then I could go thinner by stripping the white layer but I doubt I would gain a lot for the amount of effort involved.
And just to make my day the LCD on the turbine controller died - random dots flashing all over. I think the 34C outside temperature cooked the battery shed (was over 40C inside) so I've had to hack the code to use an I2C connected display that I had to hand.
Ho hum...
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Interesting winding technique frackers......
As Oz has said, just get the primary through the hole in a tidy fashion.
I ended up with one 50mm/2 primary overlapping.
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I guess im going to get in on the FUN attempting A BIG OZ Inverter. I have ordered boards for 48 volt Input ,220 Volt Output ,Split Phase............... Should be interesting! They were out of 15KW sets and don't know when they will have any so im going to get the 10 KW set. Think I might order A 24 volt set also to start with.Build my system up slowly. Anyone needing the three wire fan it is a cpu cooling fan for intel processor, or amd processor.
Im having A hard time finding toroids around here. But think I have found 2 - 2.5 KW toroids.
Also need any advice on cleaning the boards, from what ive seen they come with all sorts of crap on them....... Frank :-)
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The hunt for the ferrite 'E' cores started in earnest last night - and this turned up
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4087.JPG?m=1457602428)
Using 2 of the 'C' core sets I can make an 'E' core!!. Not sure if it will work though
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4088.JPG?m=1457602433)
I could double up the thickness and there is certainly room for the 3-4 turns of 50 sqmm wire but inductors are a bit of a mystery to me!!
Should I test a few turns and see what inductance I get? (I have a cheap LCR-T5 meter)
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Have fun frwainscott.
Yes, I see that I can not obtain any of the LF15000w, PSW,control board or power board, 50HZ 48vdc 230vac, from any source. I have sent an email to PowerJack to see whats happening.
Bit stupid on my part, that I produce a small publication to help others build their own OzInverter, and the PJ mainboards we require are no longer available ?............
PJ board cleaning.......
" Cleaning and conformal coating PCB’s.
On all my PJ boards on the solder sides there seems very limited PCB coatings. For us here, we require a good PCB coating, as the OzInverter lives and is installed in an outside building, which has rain protection, but is likely to get damp and a moist air flow.
I only do the cleaning and coating once the Inverter has been tested, and then I test again to ensure the AC voltage output is the same as before.
It has already been mentioned that the PJ Control Board has delicate resistors….. “They are very high R, so very high impedance, and easy to change the ac by even dampness or dust..... bit scary really, but seems to work in practice, but they are in the order of megohms..... if there are any problems with any of the resistors in the staircase, then the AC output voltage will move....oztules”
The spray cans I use are normal Industry standard coatings for PCB’s. The can on the left is a cleaning solvent and stiff brush, the other can is the coating but it does spray a little thicker than I would like. Follow the manufacturer’s instructions.
On the PJ Boards, underside, solder side, I remove the debris with a hand bulb blower, (watchmakers) first, and excess flux and solder splashes with the solvent and brush. But I keep the boards held vertically so the solvent runs straight down under gravity and away. The flux should come off with isopropyl alcohol and use a tooth brush.
Do not use to much solvent we don’t what that solvent removing any insulating films or heat sink pastes.
Be very, very, careful with the PJ Control Board as there are SMD, surface mount devices, on the solder side as well.
The component side gets a good blow through and if any signs of excess flux or solder splashes then its dealt with on a very individual basis, using smaller soft new paint brushes and solvent and cotton swabs if necessary.
Do not dismantle the Power board heat sinks or sub boards unless you fully understand what you are doing. Just use a soft light brush and minimum solvent use on the FET boards that you can see, remember we just want debris and excess flux removed and the board sealed only.
After cleaning, I normally allow several hours of warm air drying in a dust free environment to ensure the boards are really dry.
When lacquering with the conformal coating, I ensure, where possible, all the PCB surface gets it. Allow at least an hour between coats, I do at least 3 coats.
Allow at least 24 hours to fully dry, then a re-test of the boards to ensure the AC output voltage is as before".
Frackers.... Double thickness would put that choke about the same thickness as the commercially obtainable as recommended by 'oztules'.
Mine are 27mm thick, with the centre wrap round column 44mm long and 20mm wide. Outside is 65mm x 65mm. It seems that 3 complete turns are optimal, I tried 4 but not much improvement on idle power use, but real flipping fiddle with 4.
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try here:
http://www.ebay.com.au/itm/121372307145?_trksid=p2055119.m1438.l2649&var=420314377003&ssPageName=STRK%3AMEBIDX%3AIT
...oztules
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Thank you, and thanks about the different PJ boards that can be used instead.......
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PJ safety fan connections.....
PJ have really gone against the tide here!!
Standard PC fan with tacho has the centre pin as +ve 12v rather than the tacho pin and seeing the number of comments about putting a resistor onto the fan I assume the PJ board doesn't have a pullup resistor on it like a PC does (all the fans I have are open collector tacho output).
The other standard thing about a PC fan (CPU or chassis) is that a small molex connector is used.
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Nearly ready to run up with a current limited mains 48v supply - just need a series zener in my controller
(http://gilks.ath.cx/~g8ecj/New_Turbine/Driver-Schematic.png)
(which will allow me to measure input amps/volts) to protect the LM2595 regulator which is only rated to 45v.
All crimped and heatshrunk and overall looking good - hope it works. First light (astronomy term!!) tomorrow night I hope :)
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Your supply won't protect the fets by the way..... the 60000uf will have over 700 amps of short circuit power... itwill save the circuit board fibreglass and gate resistors, and some of the fets, but it is not current limited for all intent and purpose.
If it is wired up it will work, of it is wrong it wont.... not much inbetween I'm afraid.
................oztules
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Yeehaw - it works!!
The idle current of 1.4 amps is a bit higher than I'd like but the 'E' core is made out of 8 'C' cores of unknown vintage. Still, its less than 1% of the expected full load current.
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4118.JPG?m=1458546982)
Running it up to just over 1 kw (the maximum the test PSU can do, every thing runs cold but the 'E' core buzzes. The toroid itself is totally silent.
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4110.JPG?m=1458547005)
This is the lash-up so far, when its in a case I'll re-configure the battery bank from 24 to 48 volts (will need some re-drilling of the bus-bars). That will allow me to run up some serious load tests.
I do seem to have an excess of temperature sensors though - I have one like the one fixed to the heatsink and one like a TO-220 can with 2 legs.
Not sure about the fan - it hasn't tried to turn on yet and I still don't know if the control board has the tacho line pullup or I have to supply it as all the PC fans I have are open-collector.
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4119.JPG?m=1458547035)
I'm pleased with the way the toroid connections have turned out, having enough cable available to make a complete layer in one go I've avoided having any joins at all. The three secondary 1.8 mm wires are brought out from the final mylar layer in heat-shrink and then a lug crimped on the end for screwing onto the control board. The primary has the 14 major strands teased out into 3 lots, heat-shrink and crimp lugs again.
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4120.JPG?m=1458547051)
And the monster itself - what can I say :)
(http://gilks.ath.cx/gallery3/var/resizes/Building-a-PJ-inverter-/IMG_4121.JPG?m=1458547056)
This all gives me time to get another brew of beer going later in the week now!!
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Amazing stuff there frackers.
The extra current may be due to inter ribbon conduction between the steel laminates./
I don't know how they apply the lacquer and how well it stuck after rewing the strip... so could be eddy currents.
Also try different inductors turns on the e core. The buzz tells me you have not superglued it yet... so get some thinner wire so you can try more turns... don't need to load it so can be 10 amp wire for tests. If it makes a significant difference to go more turns, then worry about how your gonna do it then... ie maybe double up the ferrite etc etc.
When you have your best combination, then super glue it together, and it should go near silent.
Thats hard core tranny winding there.... impressed at your ingenuity.
well done.
.......oztules
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Congratulations frackers.
Its a wonderfull feeling when ite comes to life, and looks nice and tidy.
And you wound your own cores.............. The Man.....
That very slight buzzing on the E core, same here, mine is superglued, but the next one I may epoxy resin it and see if that helps. I have a feeling that the superglue doesn't particular like the ferrite?
I did get another E core spare, but to be honest, its not much noise, and the OzInverter works so well keeping the Electric on here.
My moto here, "If it works and not deteriorating, leave well alone".
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Many thanks for the pat on the back!!
It all (as usual) comes down to necessity - shipping of parts just costs way too much so even though I've been a Kiwi for only 13 years, I think I have always understood the number 8 wire mentality! (https://en.wikipedia.org/wiki/Number_8_wire (https://en.wikipedia.org/wiki/Number_8_wire)). I think my total outlay has been about NZ$550 (US$375) which includes the cost of the PJ boards and I still have enough mylar and secondary wire for another core.
I think it comes from being on an island as I'm sure Oztules will agree with - just that my island is bigger than his but further from the source of many parts that are useful (like redundant grid tie inverters!!)
5 weeks now I've been waiting on EGS002 boards, tracking is reporting that they left the country of origin 3 weeks ago :(
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This thread may be useful for people wanting to know more about toroidal coil windings.
http://www.had2know.com/technology/calculate-toroidal-coil-inductor-wire.html
Dave
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I purchased A 8 KW PowerJack, And if you look at the picture they are using a ferrite for the inductor. I counted 3 wraps and it is about 1/2 amp at idle(no load). Hope this helps.
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Oz , Clockman ,
And all of those who have put forth time and effort in these endeavors, I give my utmost thanks and appreciation.
It could not be done without these people giving of themselves for a greater good.
Here is a website that has done basically the same thing, Give or take.
http://www.lz2gl.com/power-inverter-3kw/
If you pay attention to the chokes you see they are fairly small ferites. And if you look at the picture preceding this, it is the 8KW PJ inverter I purchased, it also uses ferites,(Lower Right of the torroid) And I have checked it twice,its between 1/2 and 3/4 amps no load. I have yet to check it under load...... Waiting on batteries.... :-)
BUT CHECK PRICES It may be cheaper to buy the one Oz uses... Mine was $20.00
I am still waiting on parts, so i can get under way with my own. They just trickle in....... And am still looking for torroids, At an affordable price.
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Do you mind me asking where you sourced the monster toroids clockman, and what continuous power rating you expect the transformer to be capable of?
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Hi Fionn,
These folk will send to Europe.
They can wind toroid cores to your size but there machine is max height at 60mm.
They have a good stock range.
Just stack, and join with expoxy resin and fiberglass.
100mm hole diameter is a must. Outside say 230mm diameter, eventual height will be what you can lift and turn. Mine is at 140mm high gives me 38kg of toroid core, and that is awkward to turn and lift.
My winding table has been suitably modified, just don't want the copper enamelling scratched away each time the toroid is moved.
http://www.airlinktransformers.com/toroidal_cores/ros217/
What it will do, I am looking at 10kW, but running at 8kW safely is my aim.
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Thanks Clockman, I found the link in one of the other threads in the interim.
Some Aerosharps have occasionally come up on eBay UK but with shipping taken into account it probably makes more sense to source the cores themselves instead. Less work too without having to unwind existing ones.