You haven't try to actually look at the calculation method. Power output calculated in that sheet is proportional to window area * core cross-section as it have to be. Try to follow the references in the cells!
I must revise myself. Wire length is not neccessarily lower.
To sum up: allowable current density is related to winding thickness, inversely proportional to the square root of it. Also depends on allowable temperature rise, so can be increased in special cases with higher quality enamel.
Aggreed 100% with Pafi.
When we deal with unknown (Scrapped) lamination the first thing to do is to identify the type before calculations or rewinding.
If not we will end up like fools if the luck was not in our side and we guessed wrong.
As professionals lets' find out at least whether the lamination is M6 (lower number of turns) or M50 (higher number of turns needed - therefore require bigger window).
Pafi describes a simple test.
He says, "Indication of saturation can be done by connecting divided current signal to speaker and listening."
How do you do that Pafi?
Do you need a separate winding or windings for connecting a divided current signal ?
What do you mean by divided current signal ? Is it audio or 50/60 hz ?
Do you connect it through caps and resistors.
Please explain the method.
It will be super if a diagram is also attached.
I mean this way:
Clean sine wave would be better, but a simple 12VAC 1A trafo is still usable as source. 1 or 10 turns of secondary can be useful to measure V/turn, but not essential.
Clean sine wave would be better, but a simple 12VAC 1A trafo is still usable as source. 1 or 10 turns of secondary can be useful to measure V/turn, but not essential.
What is R1, is it 220 Ohms or 220 Meg Ohms ?
Is a 8 ohm 10 watt speaker of about 8 inches enough ?
Thanks for the circuit. Will try it today.
make the core square.
try 10mm by 10mm, try 20mm by 20mm, try 30mm by 30mm, try 40mm by 40mm.
You will find that the power (VA) goes up very close to the square of the core area.
But he breaks this rule for stacked core that are not square. I don't know why he chose to make non square cores break the A² rule.
I ran out of 1mm diameter enameled copper wire. So I ordered up 0.8mm and 1mm from wires.co (subsidiary of SWC)
They offered polyester rated at 200ºC, so that 's what I bought and it is among the cheapest of all the different insulators they offer.
i know of no rule that says cores need to have a square cross-section....
in fact you can make it any configuration you like...
i seldom made a traffo with square cross section....
in practice, bigger winding window means you can use wires with bigger cross-section and thus make for higher power,
likewise, you can use bigger cross-section core area so that you can also get more power...
these two work together, no sense arguing about things that any builder can rightfully choose...in the end it is all about choices....
in fact you can make it any configuration you like...
i seldom made a traffo with square cross section....
in practice, bigger winding window means you can use wires with bigger cross-section and thus make for higher power,
likewise, you can use bigger cross-section core area so that you can also get more power...
these two work together, no sense arguing about things that any builder can rightfully choose...in the end it is all about choices....
Milliohm. Almost any speaker is usable, but auditive skill must be developed. (Experiment with different nr. of turns!)
You're welcome!
AndrewT,
In general a square stack or to be precise 1 : 1.2 stack is the most efficient.
If you need to wind two or three secondaries as in a Tube amp power tranny then 1 : 1.5 will give you enough room at an economy.
By increasing a square stack, you can do two things.
1. You can increase the power output of the core by winding with a thicker guage.
In this case the same stack could be used as now the number of turns per volt is less and the space saved
could be used to wind a thicker guage wire as required by the increased power.
This is your method and it is very efficient and comply with all formulas.
2. We live in the real world and some times have to do things out of the norm.
If our window is not enough to put all our coils then, we can increase the window of the same lamination size
by increasing the stack height.
Now you will say that I am talking bull sh….!
Look at it this way. Let me explain.
Say you run out of window space. You add a little more of same laminations to the stack.
You recalculate for the new turns needed.(At this stage do not recalculate for power) Your output requirement is still the same.
Since the number of turns needed is less now, you can fit all your windings in the window.
Haven't we increased the size of the window by increasing the stack height?
All the windings which did not go in previously have gone in now.
Do not Worry on the efficiency.
Its like when a tube amp is on stand by where only the filaments are lit and the HT is not used in the big power transformer.
Or only one passenger driving a car meant to carry four.
Many a times its more economical using a bigger stack of the same laminations, rather than going for the next larger size.
That’s where the square rule is broken conveniently very often.
If you still don't want to give in, calculate the cost this way.
Then calculate the cost going for a bigger lamination size .
Compare the cost, After all the magnetizing current in both instances are allmost the same.
If the cost is less; You are officially granted permission to break the square rule !
Srian.
In general a square stack or to be precise 1 : 1.2 stack is the most efficient.
If you need to wind two or three secondaries as in a Tube amp power tranny then 1 : 1.5 will give you enough room at an economy.
By increasing a square stack, you can do two things.
1. You can increase the power output of the core by winding with a thicker guage.
In this case the same stack could be used as now the number of turns per volt is less and the space saved
could be used to wind a thicker guage wire as required by the increased power.
This is your method and it is very efficient and comply with all formulas.
2. We live in the real world and some times have to do things out of the norm.
If our window is not enough to put all our coils then, we can increase the window of the same lamination size
by increasing the stack height.
Now you will say that I am talking bull sh….!
Look at it this way. Let me explain.
Say you run out of window space. You add a little more of same laminations to the stack.
You recalculate for the new turns needed.(At this stage do not recalculate for power) Your output requirement is still the same.
Since the number of turns needed is less now, you can fit all your windings in the window.
Haven't we increased the size of the window by increasing the stack height?
All the windings which did not go in previously have gone in now.
Do not Worry on the efficiency.
Its like when a tube amp is on stand by where only the filaments are lit and the HT is not used in the big power transformer.
Or only one passenger driving a car meant to carry four.
Many a times its more economical using a bigger stack of the same laminations, rather than going for the next larger size.
That’s where the square rule is broken conveniently very often.
If you still don't want to give in, calculate the cost this way.
Then calculate the cost going for a bigger lamination size .
Compare the cost, After all the magnetizing current in both instances are allmost the same.
If the cost is less; You are officially granted permission to break the square rule !
Srian.
The core area squared rule is not mine.
It is the rule I see stated in many learned papers.
I am not clever enough to invent that rule.
I just happen to remember it.
It is the rule I see stated in many learned papers.
I am not clever enough to invent that rule.
I just happen to remember it.
When you say efficient, then do you mean cost efficient? At what copper/iron price ratio, and what are the other parameters? Equal loss, equal average temperature or equal current density? What is the window utilisation factor?
A statement without the original context is useless, unless it is a general trueth. This "rule" is not a general trueth, valid for only the specified circumstances. Ant those circumstances were contradictional to the case where you tried to apply the "rule".
You don't need to invent anything. Understanding is what strongly recommended. And remembering without the context is not understanding.
anyone who actually builds traffo will recognize that results of computations
on paper seldom translates to 100% realization during the actual build...
be ready to make adjustments in real-time, specially if you are just making one off....
on paper seldom translates to 100% realization during the actual build...
be ready to make adjustments in real-time, specially if you are just making one off....
how about I am going to construct more that 1000 watts transformer using this formula how can I do it?
Hi there AJT I've been to deeco yesterday to find a power transformer that is ready made and ready for install, I've seen a miyama brand transformer that is rated 50-0-50 at 6amp. that im planing to power my amplifier project, but I find it insufficient for my power requirements. Do you make a 70-0-70 at 12amp. power transformer? what bobbin and wire will be used in this spec? thank you.