Thanks Chris. I'd still like if someone could tell me how time is measured in the L=V/(I/t) equation. These things will be used, and I'm grateful for the help.
Ok so X=2 pi f L...48H. This sounds like a real number. I understand that it is still incredibly low, but if any of you know I would love to hear some figures of other 100w PP transformers.
Thanks all
Ok so X=2 pi f L...48H. This sounds like a real number. I understand that it is still incredibly low, but if any of you know I would love to hear some figures of other 100w PP transformers.
Thanks all
It's not time itself, but rather di/dt. Voltage generated by the time rate of change of current.
All good fortune,
Chris
I'm sorry; that was possibly unclear. The V in that equation is not a supplied voltage for testing; instead, it's a voltage that could be measured by supplying a changing current to an inductor. The faster you can change the current, the bigger the voltage. Example: ignition systems in the past took 12 VDC, hooked it up to the primary of a high ratio transformer, turned off the current really fast (points!) and stepped that up to 10s of kiloJolts.
So it doesn't apply to the usual method of measuring inductive reactance. (Could be used I guess, but a different deal.) The usual method is just to supply a measured voltage, measure the current, divide (V/I) to get inductive reactance X-sub-L, and calculate L from L= X-sub-L / 2pi f.
All good fortune,
Chris
So it doesn't apply to the usual method of measuring inductive reactance. (Could be used I guess, but a different deal.) The usual method is just to supply a measured voltage, measure the current, divide (V/I) to get inductive reactance X-sub-L, and calculate L from L= X-sub-L / 2pi f.
All good fortune,
Chris
Thank you so much Chris. Yeah I was wondering, and afterwards I figured it didn't apply as any of the ways I could have figured out time, or frequency, didn't come close to acceptable answers. Well except the one that I posted, but even that, 294H, sounded like the specs of a really high quality transformer. I understand the way you explained it, and I could totally see looking back at this thread when constructing a cool for something else, say a Tesla coil.
BaudouinO- good question, I'll hook it up to my scope right now and find out....Ok, it is 500Hz, just under 2V. And it does give the measurement of 14.5H. I checked my cheapo LCR meters as well, I have a few, and they were 100 and 200hz, 6v. Neither of them would register a reading on their max "20H" scales.
I'd still like to hear some other specs. It's hard to find many online, as there aren't as many 100W push pull transformers out there. At least not with a 12lb 100w core, and with inductance measurements, stating voltage and frequency.
Thanks much all of you 🙏 Soon I'll start another thread for this amp. I'm debating whether to keep it all tube PP, or to try my hand at a solid state driver and use the remaining octals for a PPP. It's starting to seem silly not to, with these specific OPTs, which are good for 318ma.
Loren
BaudouinO- good question, I'll hook it up to my scope right now and find out....Ok, it is 500Hz, just under 2V. And it does give the measurement of 14.5H. I checked my cheapo LCR meters as well, I have a few, and they were 100 and 200hz, 6v. Neither of them would register a reading on their max "20H" scales.
I'd still like to hear some other specs. It's hard to find many online, as there aren't as many 100W push pull transformers out there. At least not with a 12lb 100w core, and with inductance measurements, stating voltage and frequency.
Thanks much all of you 🙏 Soon I'll start another thread for this amp. I'm debating whether to keep it all tube PP, or to try my hand at a solid state driver and use the remaining octals for a PPP. It's starting to seem silly not to, with these specific OPTs, which are good for 318ma.
Loren
Sorry, X = 2*pi*f*L so... L = X / ( 2*pi*f)
The power rating at 30 Hz is determined by saturation, not inductance. Frequency response at lower drive levels will extend considerably lower.
The power rating at 30 Hz is determined by saturation, not inductance. Frequency response at lower drive levels will extend considerably lower.
At 500Hz the reactance of the primary capacitance will dominate your bridge reading. In fact they may look capacitive rather than inductive. You would need to take the measurement at nearer 30Hz. The primary inductance is important for the LF stability if you use negative feedback. I've used the Hammond 1650T in many PP designs and they do deliver the full power at 30Hz and produce the same LF and HF responses in simulation as the real design. The 1650T inductance is quoted at 60Hz I see on the data sheet.
You may be more successful measuring the inductance of the secondary with the primary open and then multiplying by the ratio of primary to secondary turns squared or the voltage ratio squared.
You may be more successful measuring the inductance of the secondary with the primary open and then multiplying by the ratio of primary to secondary turns squared or the voltage ratio squared.
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The old ignition systems are a bit more complicated in that they are a fly-back convertor with a 1uf cap across the points. The cap plays a role of producing the correct pulse shape and voltage. It also prevents an arc across the points on separation as the voltage takes a little time to build up. Very similar to the old TV line output stages.
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In America the cap was still called a "condenser" well into the era when points were fading into disuse. It was a hard working part, and was routinely changed in even ordinary tune-ups. And the series resistor, setting Q and also acting as a primitive CCS, was forever called a "ballast". I'd like to say that I miss those days, but it wouldn't be true. Even my 1975 airhead has electronic ignition now. Not everything gets worse. And, you kids get off my lawn!
All good fortune,
Chris
All good fortune,
Chris
The cap also reduced interference to the car radio. I remember plenty of old American cars in Cuba running without the distributor cap and the noise on the ones with a working radio.
Turns ratios were typically 1:100, so voltage across the points were in the hundreds of volts - lots of sparky potentialities.
I apologize for my poor analogy diverting the thread. Primary inductance is only important at low frequencies, and can only be judged by measurements made at low frequencies. di/dt is still real, but just doesn't matter for that purpose.
All good fortune,
Chris
I apologize for my poor analogy diverting the thread. Primary inductance is only important at low frequencies, and can only be judged by measurements made at low frequencies. di/dt is still real, but just doesn't matter for that purpose.
All good fortune,
Chris
I measured the 10k PP primary inductance for a Partridge WWFB (Williamson amp vintage) at 50Hz for excitation voltages from about 0.8Vrms to about 110Vrms, with inductance ranging from about 60H to 400H - shown in Fig 5 on p.8 of linked article.
https://dalmura.com.au/static/Williamson output transformer measurements.pdf
https://dalmura.com.au/static/Williamson output transformer measurements.pdf
Trobbins, thank you so much. What a wealth of information on your site. I too like all the phase plots being included, and I also like the feedback comparisons.
Baudouin, I will certainly try some of these measurement setups as well. I'm especially interested in the reflected secondary measurements.
Chris, no worries on hijacking the thread. I could sit and read all night about vintage systems of all sorts. Although you're right, no matter how nostalgic and engaging to remember, not everything gets worse with time. And ignition systems are one of those things. I like those types of systems for the simplicity of designing HV toys. Who doesn't like seeing a Tesla coil fire off, or a big Jacob's ladder doing its thing. I know I do. And I also really enjoy the flexibility to build things so many different ways. Big paper oil caps for example are fun to use, for that nostalgia, but geez I'm grateful that in our age I'm not forced to.
Thank you all. I will get back with some measurements. Tonight I'm sidetracked with a buddies Motorola HS-696 console pull. A little tiny push pull 12ax7>el84, with a massive PT (which I'm sure ran a preamp and maybe more).
Baudouin, I will certainly try some of these measurement setups as well. I'm especially interested in the reflected secondary measurements.
Chris, no worries on hijacking the thread. I could sit and read all night about vintage systems of all sorts. Although you're right, no matter how nostalgic and engaging to remember, not everything gets worse with time. And ignition systems are one of those things. I like those types of systems for the simplicity of designing HV toys. Who doesn't like seeing a Tesla coil fire off, or a big Jacob's ladder doing its thing. I know I do. And I also really enjoy the flexibility to build things so many different ways. Big paper oil caps for example are fun to use, for that nostalgia, but geez I'm grateful that in our age I'm not forced to.
Thank you all. I will get back with some measurements. Tonight I'm sidetracked with a buddies Motorola HS-696 console pull. A little tiny push pull 12ax7>el84, with a massive PT (which I'm sure ran a preamp and maybe more).