Transformer Size

[See_Mos]

Waste not, want not.
Heatsink the diodes to your hot water heater. 

That's a good idea

[Fanie]

The transformer got some wheels.



It will get a pull handle, the wife insisted.
On the horizontal bar I drilled a hole for the bolt to fit through, but which is smaller than the 12mm bearings.  Center to the hole gets welded two large washers top and bottom where the bearings fit into, one top and one bottom.  The steering bolt is secured on the wheel frame with a nut, then again a nut on the top bearing.  The steering wheel's frame angle is about 65deg.

The two wires from the transformer is the primary's winding.  I doubt anything residential can damage that.

[Fanie]

I decided to get proper diodes for a bridge, and 1200V 300A sounds proper to me.  I made this decision since I can get them in Anode to stud and Cathode to stud which will make the connections a lot simpler, only two heatsinks required.  And it will be a once off.  A-hand I only have to pay by the end of the month which gives me time to adjust psychologically to the price damage.

IR's data sheet indicates a Vf of 1,3V at 785A and a Vf of 1,4V at 942A peak @ 25oC.
I hope I don't make any shorts ever to reach those currents.

The device housing is around 39mm diameter and the leads are around 11mm diameter.

[Fanie]

Waste not, want not.
Heatsink the diodes to your hot water heater. 

Someone has already done this, and I have no doubt that it will work.
https://www.youtube.com/watch?v=e1pFP2a4xqg
I built a PV DC Semiconductor Immersion Water Heating Element! diode chain application

However

Solar panels are only about 20% efficient at best.  Maybe in future it will improve.  I estimate when panels get to 30 - 40% efficient, solar powered vehicles could become a reality.

For heating water you cannot beat the vacuum solar tubes, they are 85% or more efficient.  The standard tube holds about 1,5L of water, and if you place it in the sun it will boil the water away in a day.
Considering the surface area they equate to about 75W each - we get about 1000W of sun energy per square meter.

These vacuum solar tubes will work well for cooking food in them too, already done that a few times, but have a few tricks.  One advantage is the tubes inside doesn't exceed 140oC or there abouts if I remember right so unlike a heating element nothing gets scorched. The only problem is to get the Chinese to make large enough vacuum solar tubes (for me).

We've had abnormal clouded days for months now.  Yesterday we had some sun and on and off today too.
It's a bit like being sanctioned (the thing they force on you if you don't want to comply to their demands), which is a good thing, it forces you to seek solutions.

This transformer is one such a solution, it offers a much more efficient way to charge the batteries than what the inverter does with it's built-in charger.  We get fed all kinds of technological terms like MPPT which their equipment use, but is not always the best, especially under adverse conditions.

Hence, if you look at switch mode power supplies which claims near 100% efficiency it seems impressive, however in the case of a cellphone charger and the same with your PC's switch mode power supply,  from mains power they are actually power sucking devices.  The phone draws nearing 1A from mains to charge (the charging current must come from somewhere), and the 750W power supply for the PC draws up to 3,7A.  My old PC drawed a constant 2,7A measured off the mains power.

Since I have 12V solar, I use a buck converter to step the 12V up to 15V where it already works stable and draws less current than stepping up to 19V.  My current PC when idle draws less than 1 amp if idle, and when the CPU works it goes to around 2,7A.

Calculating the wats for 220 and 12V makes for a massive difference.  The 12V only supplies less than 35W where the mains switch mode power supply consumption is just below 600W.
Even if you have only mains power and you use a step down transformer, it will reduce the power consumption a lot.  Makes you wonder why the obsession with low power devices if power is actually abused.

Of course you cannot beat the sun, no wonder religions are based on sun (Sunday) worshipping, it reliably comes up every day without fail. That is why they say the sun of god is the light of the world, the giver of life, the savior of man, because if the sun doesn't come up we will die.
Using the sun for energy is like looking at the brighter side of things, you just have to look at it in a different light 

China is even creating their own sun...
https://www.youtube.com/watch?v=-wTaxzBxo6E
China's 'Artificial Sun' Breakthrough Brings Unlimited Energy Closer to Reality | World News | WION

[Fanie]

I received the diodes and discovered some heatsink I forgot that I had.
I pre-drilled the holes and as you can see it is only the thread that is in the way of them screwing in.



The thread is a weird one, 3/4" - 16 UNF, or M19 x 1,6m thread.
Who think these sizes up ? !

[Fanie]

To put matter to the madness (Or is it adding to it)
I have a 400Ah 48V battery bank supplying power to a few things as well as I run my 3D printer almost 24/7.
If the batteries are at 50% in the morning, I need to replenish 200Ah. 
At 30A it will take 7 hours in theory, but a battery also requires more time to fully charge.
On sunny days in summer we have about 8 hours the solar panels supply power, in winter around 6 hours.
Early and late hours in the day makes less power.
All that energy needs getting packed in in one day so one start the night with a fully loaded battery pack.

With this abnormal weather we had for months on end, the solar panels supplied at times as low as 5% to 7% capacity.
Hardly enough to maintain the load, never mind charging the batteries.

The solution I have is three fold.
The bakery has 8kW of panels at 220V DC and the house 220V inverter have about 5kW 320VDC solar panels.

Solution one was to add another inverter getting power from the bakery's panels and only charging the batteries..
Since Phillip does not bake on such cloudy days, I have that power at my disposal.  Made a massive difference.
With only about 20% solar power, I get around 40 to 60A charge current in total.
With the sun getting up to 50% or more, the charge current goes to 120A, which is 30A per battery pack of 100Ah.
I limited each inverter to 60A charge current (max is 80A). 
This works awesome so far and this week every night the batteries started at 100% full.
You can never have too many solar panels.

Solution two is to have a backup, and this backup is our failing power supply Exkom.
This is where the fat transformer and large diodes comes in.  As you can see you need lots of amps to fill the batteries.
If I draw just under 15A (max) then the secondary will deliver 15 x 4,5 ratio = around 60Amp.
I use the transformer because I don't want to connect mains to the inverters which then will have earth and lightning problems.
To replenish 200Ah with 60A is around 3 hours minimum.  That is, IF the power is on.
Keep in mind, if you charge the battery in the morning and there is no sun, then the night is extended to many more hours.
You may then have to repeat again to prevent the batteries from getting run down too low.That is, IF the power is on.

Solution three is a generator.  The one I have can supply 9A 220V which will equate to about 40A, and charge time will have to run 5 hours at least.
Fuel is expensive, so this will be only a last emergency measure.
I actually got the generator only to work with electric tools where there is no power.

I have four solar systems here.
One Is the water heaters or geysers, it has glass tubes and is unbeatable at >85% efficient.
I recently added another 100L solar geyser for the bakery, the other is a 250L for the house.

Two is 12V where almost everything else can work from, all the lights, my PC's modems, routers, phone chargers, alarms etc.
There is 6 independent 12V systems, because they are easy and less expensive to maintain than one big system.
IF one does have a problem, it does not affect the others.
To resolve the low solar power for these I'm going to add a pic controlled transformer that will charge the batteries when solar fail, but only after the large transformer is done.

Three is the 220VDC where everything with elements work from.  The ovens, stove plates, kettles.
There is 6 ovens, 4 stove plates and two kettles, usually only 1 to 6 ovens, 1 or 2 stove plates and 1 kettle is used.
This poor kettle boils water anything between 4 and 10 times a day.
You have to discard all the 220VAC switches and switch it with a DC circuit, mine all use a pic each.

Four is the solar generated 220VAC where fridge's, washing machine, lawn mower, TV monitors, and my 3D printer works off.
Just the things that cannot run off DC.
The 3D printer does continue if a power failure occurs, but the parts cool down and bed adhesion is lost resulting in some parts fail to print.

Mains power is only used for the workshop equipment, CNC machine, lathe, the Hermle, welding and the P&P machine.
I do however at times when there in no mains, use a lead and continue in the workshop.

The wife counted the other day and said you have 6 welders !  Perhaps she was scared I was going to get another one.
From peripheral vision I can see in the distant future when they dig us up here they will wonder what this welder did with so many pic's.

[Fanie]

I made a solar power percentage indicator from a solar cell, showing how much sun do you have.
The cell get a resistor on it's output calculated from it's specification, so that at 100% it will output x volt at full load.
This is read by a pic and indicated on a 7 segment display.  This has become the goto for everyone here to see if there is enough power for how many ovens or if the wife wants to use the ovens for rusks, or can she mow the lawn, and so on.

Interesting, on some cloudy days you can have as high as 130% solar power, just depends how the sun is reflected through the clouds.

[John Drew]

Fanie, have you thought of changing to induction for your cooktops?
They are cheap to run, great temperature control and cuts down on heat in the kitchen.
Not too expensive either.
OK, you might have to give some of your saucepans away although we found many of our cooking containers had iron in the bases anyway.  Best thing we ever did.
John

[Fanie]

Hi John, yes, actually I have.  It has advantages and disadvantages though.
Only advantage is it uses around 40 to 50% less power, but -
I had the hot plates from a hob we replaced with gas, and we got more for so cheap I couldn't refuse.
Same with the ovens.  People throw them out when they switch to gas.
One place have an oven scrap yard, we paid ZAR 50 and took two ovens there.
The induction cannot heat stainless bowls which I use for a verity of things.
Also, the element hot plates is under pic control direct off DC.
If I do go to induction heating I have to perhaps modify the circuitry, or supply with AC which I don't want to do. 
Already spoiled with the ease of using DC only 

Remember an element is a dumb and very robust thing, it does not care if the supply is 180V or 250V AC or DC, if it gets fed enough current, it works.

[John Drew]

Fair enough Fanie, horses for courses. I was thinking from a domestic viewpoint and appreciate the different requirements of a commercial kitchen. Especially if you have a DC supply. Solar at work?
We have recently converted our central hub, amateur repeater system to solar. 230V AC service charge was more than the actual power provided. So far so good.
We'll see what winter brings to our lower corner of South Australia.
John

[Fanie]

I am basically off the grid, just use exkom here and there, but depends for what.  Very unreliable, and any time it goes off, you never know if it will even come on again.

The problem is not when the sun is shining, it is when poor weather arrives, and for longer periods of time that your stuff is tested.  You can get your neck of the wood's yearly solar index off the internet, just don't mind this stupid google AI.

All I can advise is, if you have the room for it, double your solar panels, then double everything again, so that you can still get full power when you have only 25% sun available.  It's a once off expense and should see you out for the next 25 years when you should be at about 80% of the current capacity. Same with the LiFePo4 batteries, 4000 to 6000 charge cycles they will be at about 80% of current capacity...  All depends how important the system is to be up and working.

Also mount panels at an angle so they can clean when it rains.  Bloody birds like to relief themselves when they sit on the panels, and always on the panels.

Golden rule - You can never have too many panels.

Again a lot of talk on the internet about perpetual energy off late, I know it exist, but whether we will see it become "legal" in our lifetime is another question.

[Fanie]

The tap for the diodes finally arrived, so I threw everything down and tapped the heatsinks  .
Added some heat paste on the threads and base and screwed them in.
Took Ken's water heater off and that is where the diode bridge will live.

[See_Mos]

Heat sink paste is not recommended when using stud diodes.  Manufacturers of welding plant never use it. The only situation I can think of where it might be used is if the threads are not true so that the diodes are not seated correctly, even then it would only be used on the base of the device and not the threads because most types of paste act as insulation.

I gave up repairing welding gear a long time ago. the other day I was talking to a friend who is still in the trade and learned that the stupid European powers that be have banned the manufacture of traditional welding gear with real transformers and instead only inverters are allowed. 

The old style welders go on for years and are easy to fix but inverters only last a few years if you are lucky before they have to be replaced because repairs are not financially viable.

[Fanie]

You are partly correct.  They don't want you to use arc welders, for the reasons you mentioned.

There is however a very good reason to use a gas displacement welder, especially when building a trailer or when repairing structural damages on vehicles (not done any more though).  Arc welding trap oxygen inside the weld and oxidize from the inside and fail while not visible from the outside.

The other thing is of course the clean and very good welds inverters do produce.  I have 2 transformer welders, haven't used them in many years, I do however consider making a spot welder from one of them.

The inverter welders with gas displacement weld very very easy and very fast, I have two of them too.  Just don't buy a small one because their wire feeders are insufficient (I was going to use a swear word here...), or be prepared to make a proper wire feeder yourself or buy one which is also expensive.

There are newer and much better welders available nowadays, just look at the Chinese laser welders ($$$) and apparently the Germans also have a welder that welds almost everything.  I know someone who is a professional welder, one of the best in the world, who complained bitterly that any idiot can now weld anything as a result of the technology.  Somewhat like the people making hand carved doors, are being replaced with CNC machine that can do it a lot faster.

You just have to have a lot of money.  The world's only real god.  The god in religion is just for political reasons, nothing else.

One thing that is really pathetic is the water based paints.  Even with their so called stop rust undercoat, the metal keeps on rusting under the paint.  It looks like the paint skin and keeps the moisture in...

And I don't use lead free solder.

I'm almost sure the diodes data sheet mentions using heat paste or grease... ?  Most squished out when I tightened the diodes.
I used the 300A bridge this morning, and at 40A the bridge becomes a water heater too, after a while though.  It seems amidst all the wonderful this stupid world comes up with, they could not produce a decent rectifier diode.  Only way seems to use a high frequency ferrite... (and do I dare say use an ESP32 to control it, for Les's sake ;-) )
Never the less, it's almost winter, we have a sunny day today after the monsoon ? (sun shifted a lot since we last saw it) period and we can use the bridge's heat to heat the house up, although nothing beats the old wood stoves.

[trastikata]

Arc welding trap oxygen inside the weld and oxidize from the inside and fail while not visible from the outside.

Not sure about this - at that temperature I doubt you can get free oxygen trapped in the weld. Some 40 years ago when I was a child my father and I built with a stick welder a large grape arbor in the yard from ordinary steel tubing and profiles (originally from South Europe), to this day never painted and  it is still standing under the sun and rain, 10km from the coast and only some minor surface corrosion can be observed.

P.s. A friend of mine, working on high voltage transformers, gave me few boxes with this compound, any ideas what it could be used for?

[Fanie]

You used to get a lead based undercoat (Rooilood) that was absolutely awesome.  I built a trailer many years ago, and saw it once years later, also without any rust.  It was famous for stopping rust.  Not available any more, only rubbish.  They poison drinking water with fluoride but then claim lead based paints are poisonous 
Hardly any stresses in a grape vine, a trailer is subject to stresses when it moves.

P.s. A friend of mine, working on high voltage transformers, gave me few boxes with this compound, any ideas what it could be used for?

Why, it's used for compounding of course    (I will look into it when I get a chance.)

[trastikata]

Why, it's used for compounding of course    (I will look into it when I get a chance.)

Thanks for looking into this. It's a funny story - that friend came to bring me some cables I asked for and I saw in the trailer lots of those boxes with the compound. Then I asked "What is that compound doing around in the trailer" and he simply answered ... "Well, grab some if you want" - I never refuse offer like this  . Didn't ask what is it for and don't know if I need it, but it's free  .

[GrahamJ]

The Dow Corning tube is a silicon grease which is a very good heat transfer medium. I have a tube here for smearing on both sides of transistor insulating wafers. In the electrolytic zinc plant where I used to work it was used on the high current diodes that screwed into big heat sinks to improve the heat transfer. I am not sure how good a conductor of electricity it is as I only use it on insulating wafers. Good stuff you have got something very useful.

[Fanie]

I also got a tube with different name from a place, their price was ridiculous, but the guy gave me one for free, stating it is past the expiry date and I can have it !  I took it, but did mention that if it can expire then there's no use for it.  He just said doesn't matter, they have to scrap it.

Dow Corning makes adhesives also if I remember right, I saw the name before.

I dissolved silicone in turpentine and painted my steel workbench with it to prevent rust.  Works very well, only now the thin silicone layer left after the turpentine evaporated is prevent the welding to start.  I was wondering if this won't work better than the paint we have.

You can do the same with a hat or clothes you want to waterproof.  The silicone is flexible too.  Like water off a duck's back.