No, for Bdc you must evaluate that equation
∇xH - (1/c) ∂D/∂t = (4π/c) J
In few words, B doesn't change for the airgap, H does change.
B = H + 4π M
In ferromagnetic materials, the relationship between B and H exhibits both nonlinearity and hysteresis, B is not a single-valued function of H.
Magnetic anisotropy is a prerequisite for hysteresis in ferromagnetic materials, especially in GOSS, so the innocent μ is not a scalar, but a tensor.
Supposing B = μ H, with μ scalar, is only a dirty trick to deduce the equation for Bdc.
It is not easier to write the equation?
Damn!
But, what is an order of magnitude between friends?
For 13W
Uac ≈ 213 VRMS
So, with fo=18Hz
Bac ≈ 0.93T Duh!
So your transformer specs would be
3500 Ohm / 8 Ohm 70mA 13W at 18Hz. Copperloss 0,14dB.
No, wen choose Bac=0.93T, Bdc=0.76T
Bac=kBdc
L = k (Bdc S N) / (idc x 10⁸) ≈ 38 H
yes, could be.
If you use a different dc, different tube, specifications change a little bit.
If you use a different dc, different tube, specifications change a little bit.
For 13W
Uac ≈ 213 VRMS
So, with fo=18Hz
Bac ≈ 0.93T Duh!
So your transformer specs would be
3500 Ohm / 8 Ohm 70mA 13W at 18Hz. Copperloss 0,14dB.
No, wen choose Bac=0.93T, Bdc=0.76T
Bac=kBdc
L = k (Bdc S N) / (idc x 10⁸) ≈ 38 H
esltransformer your calculations are not correct for Bdc otherwise you cannot have 30W at 18Hz for 2T total induction. So you should "decide" what you want.
If you choose a smaller gap so that inductance is higher and Bdc is 0.76T then you cannot have 30W at 18Hz. L is calculated knowing the permeability, the turns, the core section and path length.
Anyway if you really had 30H you should get a quite lower cut-off (-3 dB) using a triode connected EL34. The Tango FC30 seems to be worse only because the source impedance is 3.5K......
Maybe 30H is the max value of your inductance but at low level I would rather say it is 20H at best!
If you choose a smaller gap so that inductance is higher and Bdc is 0.76T then you cannot have 30W at 18Hz. L is calculated knowing the permeability, the turns, the core section and path length.
Anyway if you really had 30H you should get a quite lower cut-off (-3 dB) using a triode connected EL34. The Tango FC30 seems to be worse only because the source impedance is 3.5K......
Maybe 30H is the max value of your inductance but at low level I would rather say it is 20H at best!
30W is not possible with a 300B
30W is not possible with only 70mA dc.
So it is just a calculation with a different current. If you use 120mA with this transformer you can have a higher output. I did not measured it.
I did say 60-120mA in my first post, not specially a 300B.
you can look at the frequency plot i already give what a tube (i used a EL34 in triode) dos with my transformer. If i use a resistor the curve looks a bit different.
30W is not possible with only 70mA dc.
So it is just a calculation with a different current. If you use 120mA with this transformer you can have a higher output. I did not measured it.
I did say 60-120mA in my first post, not specially a 300B.
you can look at the frequency plot i already give what a tube (i used a EL34 in triode) dos with my transformer. If i use a resistor the curve looks a bit different.
I don't care. A transformer is not dependent on a specific valve. You wrote your transformer can handle 30W at 18Hz with 2T total induction that's why I replied with an example on how big a transformer would be using EI's as I have never used C-core that big.....
With 120 mA DC it's even worse. You transformer will be close to saturation with 120 mA DC and 13W RMS @ 30Hz And I think you will get quite some distiortion which is already visible from the 40Hz square wave at low level....
It's not about the core but the design. You minimal figure for power loss because of winding less turns with larger wires has a consequence. If you really want to get better behaviour at low frequency you need to increase a bit the number of turns and your power loss will increase to 0.2-0.25 dB. There is no free lunch. Same applies to toroids. As alternative you could use a bigger core but then there is no size advantage over EI's in this respect.
you better look at the link i gave in my first post and look how the other transformers perform.
The frequency response of my transformer is good, better then those transformer in the test, my square waves too.
My calculations tell me that there is not a problem at the low frequencies.
What you think i am not interested in if you don't give calculations. The math you did so far was wrong.
The frequency response of my transformer is good, better then those transformer in the test, my square waves too.
My calculations tell me that there is not a problem at the low frequencies.
What you think i am not interested in if you don't give calculations. The math you did so far was wrong.
You better stop with your nonsense!
You wrote " The transformer is a single ended double HiB c-core 3500 Ohm / 8 Ohm 60mA-120mA 30W at 18Hz. Copperloss 0,14dB. "
If you have 0.76T Bdc with 70 mA, it means that Bdc with 120 mA will be 1.3T and you cannot have 30W at 18Hz with 1860 turns and that core size (15.32 cm^2 and 25.9 cm path lenght) in BOTH CASES. With 120mA you cannot even have 13W @ 18Hz which require 0.93T.
This is not opinion!
I told you how to calculate it in the previous post and also the equations have been already written by Popillin. They are the same!!
It is you having problems with the subject.....30W at 18Hz means 1.42T Bac so your total B at 70 mA is already beyond saturation if Bdc is 0.76T.
If 30W at 18Hz is true then your Bdc can only be 0.58T and so your inductance cannot be 30H. They are all interdependent quantities you cannot pick them up arbitrarily.
From your frequency response measurement I say that you don't have 30H inductance and I could bet on this.
There is no mistake. It's just that you do not consider I could use a different model.
I don't want to be specific as I don't want to tell about my winding technique just like the others do!
However if you had some real practical experience with this issue you would know that you don't need that complicated model for capacitance as it won't work so well in general. For the SE case the effective shunt capacitance will be about 1/2 of the total static capacitance with the secondary grounded and 1/4 for floating secondary. My practical model is basically made of two nearly identical (because the contribution of the single windings is not precisely the same) shunt capacitances equal to 1/2 of the total static capacitance C (that you can measure directly). So when you have the secondary grounded the effective capacitance is 1/2C and when floating they are "all is series" and you get 1/4 of total static capacitance! This will be quite general behaviour. For example you can check the Monolith Magnetics transformers where you get the shunt capacitance value in the specs with and without secondary grounded and you will see that the ratio between the two values is nearly equal to 2 in all cases with very good approx.
Single Ended Output Transformers - Summit product line
Anyway, the best way to know the precise value of shunt capacitance is measure the resonant frequency and the leakage inductance and derive it from the formula that defines the resonance. Until now no-one has bothered in developing an accurate model for capacitances in my knowledge for this tipe of transformers, firstly I think because different winding techniques results in different total capacitance overall and secondly because HiFi OPT's represent a small fraction of the entire transformer market....
Bla, bla, bla you change opinion according to how the wind is blowing! You really don't know what you have in hand, I am afraid.
If your transformer is in line with those in that link then your inductance is rather low for the size. Frequency response and square wave response at low level is the only thing I can compare. And that is.... Most of those transformers at least are small in size! Your transformer is heavier than mine on EI120 40x50 core that is already not small at all but reasonable for certain applications....
Compare your transformer to the Tango FC30 in the same conditions and you will see that is not better at low frequency. The FC30 has 20H minimum inductance and 25-26H already at a fraction of 1W. I say that you don't get here with you transformer!
As I told in the beginning there is nothing you can teach Japanese about transformers expecially considering your level of knowledge of the subject and inexperience with amplifiers....
My model is incomplete, because does not take account each winding capacitance, but as I said before, HV circuits only allow series primaries, so that capacitances are all in series and can be neglected compared with distributed interwinding capacitances.
When distributed capacitance is lowest, winding capacitance is not negligible anymore, as can see with very simple winding pattern
Bingo!
Both models match for short circuited grounded secondaries, and it is consistent with a shield between P and S.
Hmmm, seems to me that your model works with simple winding patterns.
I'm a poor TV repairman and I don't know from many brands, but I can assure you that my model is pretty close to reality, especially with complex interleaving pattern, unfortunately measurements were taken with a friend's old equipment, and I haven't any plot or picture to prove it.
And for your mistake, I mean this
It is not a mistake! The effective shunt capacitance for PP is 1/4 of the total static capacintance already with secondary grounded. So according to my model is like the capacitance in the SE with secondary floating are like if there were all in series as I use the same simple empirical model for both....you don't need complicated models. If you always leave a little bit of room for more insulation you can start with one and then increase it if you need. Beware that the minimum insulation you need is not just that related to DC voltage.
Last edited:
- Status
- Not open for further replies.