Iron core toroid test at 1 kHz square wave

"P E Schoen"

This is intended for about 1 kW output, but that will require a more powerful voltage source and conductors that can handle 50 amps. But it appears that the transformer has no more than 17 watts of core loss with the

** Are you on the same planet as the rest of us ??

That puny core is suitable for an 80 VA tranny for a simple reason - temp rise.

An 80 VA toroidal tranny has about 10 % losses - mostly copper loss.

So, the running temp reaches a safe max at 10 watts loss in free air.

What power loss are you looking at ?

The thing will be smoking hot unless you blow a ton of cool air over and through it.

... Phil

Excellent! The data given seems to imply that there is less percentage loss (lower relative drive current WRT drive voltage) as the drive voltage is increased; making the overall efficiency higher as drive voltage is increased.

I would suggest you keep those wires separate all the way to the battery connector - that way the wire resistance of each leg would end to balance or equalize the currents.

I have wound more transformers than i can count, using a guide printed in Popular Mechanics, Little Library of Useful Information #41, "Home-Built Transformers" second printing 1944 and for all practical purposes there was NO copper loss at full power and all of the transformers ran cool. Furthermore, there was always a little extra room in the window(s). And for toroids (which was not covered eXplicitly) there is always plenty of room by default if one follows the guides.

There were only two exceptions: i wound them specifically for high current load and short term use; in fact i still have one of them; i believe it is a 50W core, output at 1A test load of 1.45V with 20A max design semi-continuous load (wire gets Baer-ly warm) and capable of 80A for short term use (wire gets hot after about one minute). This is a loose-goosey wiring where one large-sized conductor (or better) flat strip would give much lower copper loss. I used 5 turns each of four #18 twisted wire, knowing that was not adequate for lower loss (#18 was largest wire on hand). I should have used at least six #18 wires in a flat lay arrangement; the twisting ate up too much room in the windows (no...NOT Micro$uck) but there is still room to spade nonetheless.

Talking about mags.

I still have every issue, - the lost one's of Popular Electronics since I was thirteen up until they stopped publishing on the rack. And a few here and there when they attempted to restart it with some variant authors that didn't seem to touch in areas of my interest.

Lots of interesting reading there. :)

Jamie

How egotistical to think anyone cares about your pathetic personal life, Maynard. Shut up!

Well, you took the time to read it and respond, so I guess I have some interest out there.

Jamie

And you're presumptuous, too.

I see :)

Jamie

Core loss is usually specified in Watt/LB. ~2ish watts/lb is generally acceptable. But it depends upon heating and temp rise and duty cycle and cooling.

Cheers

(lower=20

battery=20

This test was done under far from ideal conditions, so the figures = represent=20 a "worst case" scenario. The power supply leads were #22 test clip leads =

about 3ft long, and the wires going to the transformer were #18AWG about =

The transformer windings are significant with about 4 ft of #10 primary = at=20 about 0.004 ohms. At the design target of 50 amps, it's 10 watts each, = but=20 they are mostly exposed to free convection so they might not get = extremely=20 hot, and I have room for heavier wire or multiple strands. The secondary = is=20 about 70 ft of #18 or about 0.5 ohms. At 1kVA design target of 160 volts = at=20

So Phil is right about his 30-40 watts estimate. But my goal was mostly = to=20 determine the core loss of an iron core toroid at 1 kHz, and then = proceed=20 with more detailed design analysis to determine the limits of what is=20 practical. Perhaps just 8x (480 Hz) and 640 VA continuous is more=20 reasonable. I suspect the core losses would drop to less than 10 watts, = and=20 copper losses maybe 6+8 =3D 14, or 24 watts total.

My tests also indicate that a toroid such as this might be good for = audio=20 applications, especially when used at the design rating of 80 VA. That = would=20 be at a primary voltage of 4 volts 20 amps, where core loss at 1 kHz is =

unless a system required most of its power at that frequency, a "normal" =

audio signal of about 5 kHz average would have only 10 watts loss or =

Paul=20

"P E Schoen"

So Phil is right about his 30-40 watts estimate.

But my goal was mostly to determine the core loss of an iron core toroid at 1 kHz, and then proceed with more detailed design analysis to determine the limits of what is practical. Perhaps just 8x (480 Hz) and 640 VA continuous is more reasonable. I suspect the core losses would drop to less than 10 watts, and copper losses maybe 6+8 = 14, or 24 watts total.

My tests also indicate that a toroid such as this might be good for audio applications, especially when used at the design rating of 80 VA.

That would be at a primary voltage of 4 volts 20 amps, where core loss at 1 kHz is 2 watts. If proportional to frequency, it would by 40 watts at 20 kHz,

For a given transformer, core losses go DOWN as input frequency rises because magnetisation of the core is inversely proportional to frequency.

For example, a mains rated toroidal with 120V, 60Hz primary can be used for audio from 60Hz to 100kHz at rated voltage and power or from 30Hz up if the input voltage is kept below 60 volts rms.

Core saturation at low frequencies is your only concern.

... Phil

"Robert Baer"

The busses don't stop where this dude lives ....

.... Phil

Actually, i found it interesting at minimum that someone had the personal interest and wisdom to save all of those issues for so long.

Well, obviously there were core losses at full load, but total losses were low enough that the transformer(s) did not seem to get warm.

"Robert Bare Faced Liar "

Fuckwurt.

... Phil

were=20

There will always be significant copper and core losses which result in=20 heating and reduced efficiency as the watts (or VA) per cubic inch = increase.=20 There are always tradeoffs between efficiency and size and cost of = materials=20 and other factors. But any transformer that does not exhibit any = noticeable=20 temperature rise must be of a rather trivial design with very low power = for=20 its size.

I could not find anything about the Popular Mechanics article. I have = also=20 wound numerous transformers, and some of them were not really very good=20 designs, because I had little concept of winding resistance and heating = when=20 wound in layers. I typically tried to get more voltage out by increasing =

secondary turns, and "wound" up getting less than expected.

When I "discovered" toroid transformers, I thought I could make high = current=20 transformers for circuit breaker testing much smaller and lighter than = their=20 E-I cousins, and I thought I could save even more weight (and cost) by = using=20 aluminum bus bars. But when I built the first prototype using three 1.4 = kVA=20 cores, I was disappointed in the output I was able to obtain. It = improved=20 much when I used copper bus, and I also discovered the importance of = clean,=20 tight connections. But I also discovered the limitations caused by = internal=20 impedance and inductance effects of even apparently short sections of = bus.

Eventually I designed and built a successful toroid transformer with 5.6 = kVA=20 continuous rating and capable of over 10,000 amps into a short. Even = with=20 this experience, I ran into difficulties with a larger design, but that = was=20 because the primary cores were not designed to provide the maximum flux = at=20 rated line voltage. The design would have worked if I had removed about =

project and instead go with a C-core design. We finally got that right = and=20 now it is capable of producing about 10 VAC at peak currents close to=20

Paul=20

_I_ never doubted it.

That's magnetic hysteresis losses right? And eddy current losses are proportional to what? V^2 like a resistor? so at, or below rated voltage they won't be a problem.

frequency.

In the interests of completeness and curiosity, I repeated the tests at =

Under no load conditions 500 Hz, I got:

With a 1k 10W resistor load:

Under no load conditions 1000Hz, I got:

With a 1k 10W resistor load:

Under no load conditions, 2000 Hz, I got:

With a 1k 10W resistor load:

At 4000 Hz with a 1k 10W resistor load:

At 8000 Hz with a 1k 10W resistor load:

At 16000 Hz with a 1k 10W resistor load:

4V 0.26A 1.0W 94.5V P-P

I interpret this to mean that magnetic hysteresis losses drop as a = function=20 of frequency. And of course this is at very low current. Will there be = other=20 core losses that increase with current?

Thanks,

Paul=20

One day, you may learn to read - and then and only then you might begin to understand what was said and/or implied. ALL of the transformers (except the two mentioned) did not seem to get warm at full load; EXACTLY what i said in the sentence you blithely quoted above.