Can't find the transformer I need so need to build my own

[kellys_eye]

Figure on fire and smoke! AC mains transformers require laminated cores to operate at 50/60Hz. Ferrite cores are made to operate in the 10's of kHz region (and more).

Any transformer you obtain/make/use will only get you in the BALLPARK for the volts/current you need. You really do need to use some form of regulation/control of a fixed (preferably) DC input else the ouput will not be regulated i.e. it will vary with load.

We have already pointed to commercial solutions (ex server PSU's for example) which will be a lot cheaper, vastly easier and a LOT safer.

Please learn more about transformers and supply regulation - it's not 'simple' and armed with that knowledge you might have an appreciation of why we aim you in the direction we do.

 

[Harald Kapp]

Look up transformers for arc welding. These might be in the ballpark of your requirements

 

[Minder]

SMAW Arc welding transformers cannot maintain the voltage when high current flows, they are designed with high voltage output in order to strike the arc, as soon as the arc is struck and current flows, the voltage collapses but high current remains.
The have an adjustable shunt in order to create this and adjust the arc current accordingly.

 

[brandnewb]

At the risk of cursing in the church....

Let me please start by stating that I mean no disrespect to either this community and to (high voltage) electronics what so ever for what I am going to say next.

Although very much appreciated links to hard core scientific documentation regarding transformers my mind is not suitable for that kind of detail.

Also this pandemic, which hopefully is over soon, has made me realize I need to learn how to make shift all kinds of useful stuff for when the s*(t finally does hit the fan.

So may I please ask for tips and tricks on how to go about this the crude way?

Currently I am 3d printing a cast for a huge silicone toroidal mold to cast into a high temp fast setting resin with a whole lot of iron powder added to it. I am in the process of finding out how much iron powder is too much (i.e. the cast starts conducting electricity)

Please forgive me for the poor/dumb mans mind set. It's all I got but need to move on!

a shape cut in half for the silicone mold to be made with. then comes the iron filled resin


the idea here is to over size rather than calculate. I mean at some size and magnetic permeability level things need to start working right?

i have also planned for a ground wire to be embedded in the resin cast of the core in case that makes sense

 

[brandnewb]

If I give the primary coil 380 winds (760 turns) with 0.4mm enameled copper wire
and the secondary coil 6 winds (12 turns) with 5x1mm (with the ends soldered together) enameled copper wire. Is my math correct in where I should get around 3.65V output minus some losses?

I have found earlier down the road that stringing strands of insulated wire to form a single large wire does not work to allow for higher amps. We need a single (multiple conductive strand) core.
Just thought of sharing this for newcomers like me

 

[brandnewb]

I think you'd better have a fire extinguisher handy. Mains primaries normally have a LOT more turns than that. Im sure some other member here will have the figures/maths.

With my latest attempt (extra large toroidal core) would you recon that 630 turns for the primary is good?

It is a toroid with a 5cm diameter spanning a 18.5cm diameter.

Or should I go larger?

 

[bertus]

Hello,

Later down the line I am looking to transform 230VAC 16 amps to 58.4VDC at 140 amps.

You can NEVER get more out than you put in.
230 V X 16 A = 3680 Watt
58.4 V 140 A = 8176 Watt

The EDUCYPEDIA has a couple of pages with info on transformers:
Transformers
Transformer types

Bertus

 

[brandnewb]

Hello,


You can NEVER get more out than you put in.
230 V X 16 A = 3680 Watt
58.4 V 140 A = 8176 Watt

The EDUCYPEDIA has a couple of pages with info on transformers:
Transformers
Transformer types

Bertus

yes thank you for the heads up

 

[brandnewb]

Hello,


You can NEVER get more out than you put in.
230 V X 16 A = 3680 Watt
58.4 V 140 A = 8176 Watt

The EDUCYPEDIA has a couple of pages with info on transformers:
Transformers
Transformer types

Bertus

I do have a 3 phase mains connection of 3 x 25 amps. So for the lower requirement scenarios I can also by pass the 16 amp circuit breaker and hook up directly to one of the 3 25 amps lines (which have their own grid supplied 25 amps breakers.)

Any hope left?

 

[crutschow]

I correct in assuming that it is the diameter of the secondary coil wire that determines the output amp range?

Since roughly equal power goes through the primary and secondary windings, the primary wiring size also must be properly selected.

 

[brandnewb]

Since roughly equal power goes through the primary and secondary windings, the primary wiring size also must be properly selected.

yes, so now I have diam. 1mm enameled copper wire and planning on winding it 630 times.
for the secondary I will wind the 8mm diam (50mm2) wire 10 times as to hopefully get 6.65VAC (EDIT: 3.65VAC)

I mean 1mm diam primary wire is nothing to sneeze at is it?

but if it is have no fear, I can get any diam enameled copper wire if need be. even spools of 20KG

the idea here is to over size rather than calculate. I mean at some size and magnetic permeability level things need to start working right?

Is there anyone that can debunk this statement?

I do have a 3 phase mains connection of 3 x 25 amps

That is 3 x 25 amps at 230V. I am assuming we can get serious with that can we?

 

[brandnewb]

if I deprive my whole household of any power I could in theory pump 3 x 5750 watts (17.25KW) through any load I might care to envision right?

that is before the 3 x mains grid 25 amps breakers break. I have not gotten into the subject yet of having a potent battery bank and having it discharge at 1C (280 amps)

 

[bertus]

Hello,

3 phase transformers can be configured in many ways.
This page will give you more info:
https://www.electronics-tutorials.ws/transformer/three-phase-transformer.html

Bertus

 

[brandnewb]

yes thank you, so given my track recod of not being able to understand such hard core science I am assuming that your answer is;
yes we have got something to play with here?

 

[bertus]

Hello,

An 10 KVA transformer would have a weight of about 75 kilogram.
See the attached (german) folder.

Bertus

 

[brandnewb]

Hello,

An 10 KVA transformer would have a weight of about 75 kilogram.
See the attached (german) folder.

Bertus

ok, no problem. I can buy spools of wire at 20kg and I can print any mold for an high temp epoxy iron filled core.

are we still on the same page or am I assumed to dive into subject matter that is hard for me to understand

 

[kellys_eye]

Iron filled epoxy core WILL NOT WORK with standard AC mains frequencies. You are creating (effectively) a 'dust iron' core which will only work at higher frequencies.

If you want a core for domestic AC frequencies you either need laminations (E/I, C/T etc) of a single 'strip' would into a 'coil' as would be found in a toroidal transformer.

This forum doesn't encourage 'unsafe' (let alone 'improbable') working and you are certainly skirting this area - you are aware of just how dangerous multi-kW of electrical energy can deliver? Physical injury/death is quite likely and your inexperience and lack of understanding is causing me (at least, probably others) much cause for concern.

From what I can gather you do not even NEED the current levels you're proposing so why bother?

 

[brandnewb]

Iron filled epoxy core WILL NOT WORK with standard AC mains frequencies. You are creating (effectively) a 'dust iron' core which will only work at higher frequencies.

If you want a core for domestic AC frequencies you either need laminations (E/I, C/T etc) of a single 'strip' would into a 'coil' as would be found in a toroidal transformer.

This forum doesn't encourage 'unsafe' (let alone 'improbable') working and you are certainly skirting this area - you are aware of just how dangerous multi-kW of electrical energy can deliver? Physical injury/death is quite likely and your inexperience and lack of understanding is causing me (at least, probably others) much cause for concern.

From what I can gather you do not even NEED the current levels you're proposing so why bother?

yes understood. I will once again admit I am way out of my league here and I have already stated to mean no disrespect. Just please allow some time for me to get a grasp.

Given this that seems to mean there is no way for me to actually test the Lifepo4 cells at a charge rate 0.5C (140 AMP).
I can live with that as 14 of the 16 cells seem to be ok at a 0.01C discharge rate clocking in at 286 Ah.
What I did was to hook up the 16 cells in series and run a battery tester (I have gotten a second one since my first one I blew up and is still in the process of being repaired(not a high prio at the moment)) at around 2.8 amps. and kept monitoring the voltage level on each individual cell.

2 of the 16 touched 2.5V well before the other did so I stopped the test. However the total amount of Ah was already at 286 so that in it self is good news.

I can run the same slow test again for those 2 cells and if they have 280Ah capacity then simply trust they are ok.

 

[kellys_eye]

If the cell discharge rate meets with the specifications then by default they MUST be charging to their full stated value. You do not need to charge them at 1C to prove that. Charge them at a rate you are capable of achieving - or plan to use during NORMAL operation.

As long as they deliver the full stated capacity then they are 'good to go'.

 

[brandnewb]

Hello,

An 10 KVA transformer would have a weight of about 75 kilogram.
See the attached (german) folder.

Bertus

I seem to be changing my mind ;( if you can direct me to a 230VAC 50HZ -> 3.65VAC (50HZ) transformer I will conciser buying it. If not like more than 500 euros