Transformer efficiency - Z-11,H-14, c-core, r-core , toroidal

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High guys!


Need your pointers on the percentage of efficiency for the different type of transformer core. I've tried to search it in this forum n google it from the internet, but so far I only managed to find that toroidal has about 80-90% efficency n R-core has a better efficiency than the toroidal. I just need a percentage of efficiency for Z-11, H-14 n C-core transformer coz I plan to order a transformer for my power amp project. Just don't wanna make a mistake of ordering one n at the end found out that I've made a mistake of ordering a lower value one bcoz I did not take into account about the transformer lost of efficiency. Hope u guys can share some infos. Thanks!



Cheers!

Eddy.
 
flyboi said:
High guys!

Just don't wanna make a mistake of ordering one n at the end found out that I've made a mistake of ordering a lower value one bcoz I did not take into account about the transformer lost of efficiency. Hope u guys can share some infos. Thanks!

Cheers!

Eddy.
Umm, what is your problem? If you order 300VA trafo it outputs 300VA no matter if its 80% or 99% efficient. ?
BTW. Toroids can be custom-ordered for higher effiency also.
 
Its hard to believe that R-core could have higher effiency than toroid. Sure either of these types can show higher effiency if different materials or different amounts of material are used. For example reducing core losses and using more copper for wiring effiency can be improved, but this increases price drastically.
 
Re: Re: Transformer efficiency - Z-11,H-14, c-core, r-core , toroidal

mzzj said:

Umm, what is your problem? If you order 300VA trafo it outputs 300VA no matter if its 80% or 99% efficient. ?
BTW. Toroids can be custom-ordered for higher effiency also.

Hi mzzj!

Thanks for your reply. Actually i'm very green on this subject n need a clarification. From your explanation, let's say if the trafo has 60% efficiency, the output will still be 300va. But bcoz of total lost of 40% in efficiency, wouldn't it perform like a 180va trafo? So, based on your explanation, a 300va trafo will still have a sonic or performance of a 300va transformer eventhough it hast lost 40% efficiency. If that is the case, I should not be to worry about efficiency then. Thanks!


mzzj said:
Its hard to believe that R-core could have higher effiency than toroid. Sure either of these types can show higher effiency if different materials or different amounts of material are used. For example reducing core losses and using more copper for wiring effiency can be improved, but this increases price drastically.


This is what I found during googling lastime. So, I must be wrong. Thanks for the highlights.


Cheers!


Eddy.
 
Re: Re: Re: Transformer efficiency - Z-11,H-14, c-core, r-core , toroidal

flyboi said:


Hi mzzj!

Thanks for your reply. Actually i'm very green on this subject n need a clarification. From your explanation, let's say if the trafo has 60% efficiency, the output will still be 300va. But bcoz of total lost of 40% in efficiency, wouldn't it perform like a 180va trafo? So, based on your explanation, a 300va trafo will still have a sonic or performance of a 300va transformer eventhough it hast lost 40% efficiency. If that is the case, I should not be to worry about efficiency then. Thanks!


This is what I found during googling lastime. So, I must be wrong. Thanks for the highlights.

Cheers!


Eddy.

Transformers are rated by output power, so 300VA transformer can supply 300VA no matter what effiency. Difference is how much power that transformer is drawing from wall outlet. 300VA transformer with 60% effiency needs 500VA from outlet, and 90% efficient transformer takes 330VA. But amplifier have same 300VA availlable in both cases.

Googling is highly recommended, but when it comes to audio-related stuff you have to assume that 80% of information is snakeoil and BS.
 
Efficient is often attribute to design
Z11, h14,m19 are transformer grade which just reflects the core loss at 1.5 T. Z11 is 1.6W, h14 and m19 are 3.5w.
Maximum T for z11 is 1.75 to 1.8(high B). While h14 and m19 is 1.6

In reason times transformer designers have often increase this T figure to say 1.1 T for m19 and higher for the m6/z11 series. This way they can pack more va into the same trans. However this inturns reduce the efficiency of the design. But due to rising more like sprinting markets in india and china. Shipping cost needs to be reduce Thus making transformer design less efficient just to save weight. Amp manufactures like sony and others, find that their biggest cost is the transformers. It weights down their amp to much.

What happens this states that z11 is able to take higher T thus allowing more overloads. What happens when the mag field goes close/ than bigger than maximum T for the material, the material cant hold the magnetic field and start to emit lots of mag field.
what happens is that All transformer whether c,ei, o(toroidal), r will always emit this mag field.

However do note ei mag field is radiating along the axis of the copper wire while r and o emit this field within its hole thus preventing spraying of mag field everywhere.

In our normal practice when making audio transformers, we specify our designs of Z11/m6 to run at 1.05 T to reduce power loss. Eff of up to 90% is acheivable. This inturns sacrifies lots of va in return for efficient. Being an audio fan. I have studied that lowering the va and bring up eff is offten very beneficial to audio. THe music just flows better period. It often pays to get custom wound trans for an audio transformer winder. The benefits is often more inreturns than a blackgate, no run in requires just the big jump in performance. Being custom allows the insertion of E.static screen which is so beneficiary in audio. Everything is quieten down due to this

Also in reason time toroids vs EI core question has often come up. I believe at lower va say 10-300va standard toroids have a better edge over standard EI. However everything above 300va some how EI just have the music in hand. This is because they require less current when turning on, don't saturate with dc involve unless excessive. This result is thru blind testing. So no maths involve to prove other wise. Most Japs, avoid the use of toroids and often still stick to EI core transformer due to this .

When custom making smaller trans ask the vendor to spec the mag field to 1.05T to 1.08T with e.static screen and goss shield and you will see it beating the run of the mill toroids in this class

Hope this info helps to clear some doubt.
Nicholas
PromitheusAudio
 
Transformer effiency depends on the power rating, low power are typically very poor.

Not all the time. It depends low power transformer tend to be design at high power loss than their bigger brothers. From the rdh book ver 4 it states than when design smaller trans like E76 to E48 they use a Tesla factor of 1.4 T. Because its a smaller trans it can capture more mag field and loss is per kg so most small size are sometimes design this way.

Again as stipulated design at 1.05 T using z11 will change your whole perception
Also rating it for 240V is wise as the trans designer will incoprate more turns to account for the higher voltage

If u are refering to Jalan Pasar transformer in Malaysia, then your above statement is right. Most of the transformers there are using rather bad grade iron higher than h14 someinto h23/30 which is 5 watt per kg power loss plus they underspec it to meet the price. general this are the worst transformers period.

Best regards
nicholas
 
Hi,
I am very surprised you are quoting transformer efficiencies below 90%.

I would expect all 200VA plus transformers to be above 94% and some of the better ones approaching 97%.

The very small numbers i.e. n (eta)~= 80% might apply to the 3VA to 20VA wall wart types that are produced down to a price and not up to a performance specification.

To support these views, look at the regulation values quoted. Many of the audio sized toroids are in the 6% to 4% range implying 94% to 96% efficiency.
Or is regulation a poor predictor of efficiency?
 
If my 2d year highschool memory doesn't fail me efficiency of a transformer is determined by: output load, core losses, power losses.

Efficiency = output power/(output power + core losses+power losses) x 100

Core losses depend on the hysteresis of the core, power losses on the resistance of the winding wires.

The regulation factor can be linked to the loss factors, but it is only part of it. A lower output voltage at higher output currents does not change the VA rating.

Efficiency of really large voltage transformer setups on board of ships are taken as 90%, higher efficiency can only be achieved with solid state switching.
 
jacco vermeulen said:

The regulation factor can be linked to the loss factors, but it is only part of it. A lower output voltage at higher output currents does not change the VA rating.

Good point. If someone wants to calculate effiency I think it can be calculated from idle losses and regulation factor. Sometimes but not always transformer manufacturers publish idle losses so those can be used to calculate effiency.
 
Hi,
I working in the dark here, but let me expand on my regulation statememnt.

If a transformer with open circuit secondaries shows 100Vac and when fully loaded this drops by 5% to 95Vac (from the 5% regulation figure) then the efficiency is output voltage *output current/input voltage*input current.
We know the input voltage has not changed and that the output voltage and output current are specified. This leaves just the input current as the unknown in the efficiency equation.

Does anyone have readings of the input current for normal audio toroids when working into resistive loading (when regulation is valid) at the rated manufacturer's output?

I would expect the input current to be very close to the theoretical figure that gives the 95% (100%-5%) output.

Do you pragmatists have some real numbers?
 
I'm planning on building a simple 5 VDC, 2 A linear regulator using an R-Core transformer. I got the tranny from Japan with the following specs:

Dielectric breakdown: Pri-Sec = 4000VAC/min
Efficiency = 83%
Off Load Current = 4mA
Frequency = 50Hz (will this be a problem for U.S. 60Hz operation?)
Regulation = 15.5%
Insulation Resistance > 100 MOhms at 500 VDC

Primary, Secondary
Direct Current Res = 17.47 Ohms, .21 Ohms
Off Load Voltage = 120 V, 11.79 V
On Load Current = .4 A, 4 A

I'd like to get some opinions about how well this tranny might do for my linear regulator.
 
Hi Tonyptony,
that transformer has a voltage that is a little high but still perfectly useable.

The 11.79Vac open circuit voltage will fall to 10Vac when fully loaded to the 4A specified, making it a 40VA transformer.
You are planning on using upto 2A so the average output voltage will be about 10.9Vac but a little less due to the capacitance loading after the rectifier.

Peak capacitor voltage will be 16.2Vdc less a diode allowance of about 0.5V. Use 25V rated caps.

Running voltage when on full load will be about 14Vdc.
You have to lose 9V @2A leaving 18W of dissipation. Allow for this, it will require a big heatsink.

All these voltages will increase if your mains supply rises. Re-check the dissipation @ max mains supply voltage from your supplier. Similarly you need to check your output voltage less diodes loss and ripple to ensure the regulator sees enough voltage to allow for 5V plus regulator minimum drop.
 
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