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Re: S-38B Tuning Shaft Query
<grins> Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Monday, August 5, 2024 at 01:20:26 AM CDT, Richard Knoppow <1oldlens1@...> wrote:
Not much. I don't drink much soda of any sort and don't use lo-cal sweeteners (or sugar for that matter). I don't think I can blame my bad memory on that. Curiously my memory is very good for some things. I have reached the age (83) where I take a lot of meds, its possible they may exaggerate the problem, hard to tell. In my mis-spent youth I never took anything, not even aspirin. Things change. Its hard to tell about general intelligence; although its not supposed to improve with age mine has in some cases. I run across things in text books that used to puzzle me that now make sense. I also find that life remains fascinating. A friend, now SK, used to say that she just resented that she would never live long enough to find out how it all comes out. On 8/4/2024 7:53 PM, Gordon, KJ6IKT wrote: Hi Richard, --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden You said: "By transitivity, then, primary current and primary voltage are in phase with each other." No, this violates all that is known about inductors and coupled inductors aka transformers.? Easy enough to prove to yourself by using your o'scope on the primary winding to measure both current and voltage simultaneously. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, August 4, 2024 at 08:43:16 PM CDT, HF via groups.io <incorridge@...> wrote:
Hi Jim,
The purpose of monitoring primary current is to understand how the transformer's operation affects the power source.? The purpose of monitoring secondary voltage is to understand how the transformer might generate a higher-than-normal voltage that could cause an internal insulation failure.?
Image 20 posted earlier shows that primary and secondary voltage are in phase with each other.? Many other images show that primary current and secondary voltage are in phase with each other.? By transitivity, then, primary current and primary voltage are in phase with each other.? If they were 90 degrees out of phase then no power would get into the transformer and it would have nothing to transform.
Cheers,
Halden VE7UTS
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Don There is no difference between two inductors and a transformer if the two inductors are coupled together only by a common magnetic field.? The tighter the coupling between the two inductors, the more power that is transferred from one inductor to the other.? In other words, they transform power from one to the other. If you are skeptical and you have a working radio or power amplifier with a 70 volt audio output, you can collocate? two 70 volt line transformers on the bench.? Connect one to the 70 volt audio using the 10 or so watt tap and terminate it's output in an 8 ohm power resistor.? Connect the other line transformer output to an 8 ohm speaker.? Set the volume control for a decent volume.? The closer the two line transformers are to each other, the more audio that is coupled from one line transformer to the other and then to the speaker.? Perhaps the highest volume is when one is stacked on the other.? I have done this experiment. This may help explain why some radios always have a slight hum in the speaker if the power transformer and the audio output transformer are collocated on the chassis. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, August 4, 2024 at 07:15:06 PM CDT, don Root <drootofallevil@...> wrote:
Hi jim I think many and me/I would agree with paragraph 2, and 3, but on pgf 1, with all due respect, this is a transformer, and it has some ?resistive load which is reflected to the primary as-in phase current, and likely[must] dominate ?the steady state currents and the current at turn on. If these loads were not there we would see the magnetizing current [as you suggest I think], as transients and as steady state, and ?it would be interesting to know these too, even under low voltage. ?The fact that you/I can barely see and phase shift between voltage and current, proves the large dominance of the resistive load over magnetizing current. Sorry jim, I would not want to see Halden derailed by pgf 1 , but I hope you reconsider it, taking everything into account. My comment is well meaning, though It might not sound like that s, my fingers have deteriorated into hunt and peck with mostly errors, so there is a lot of hysteresis going on here, or reactive power. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, August 4, 2024 7:38 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Halden And that is the problem, there should be a phase difference between the two if you measure voltage and current in the same winding.? Measuring current in the primary and voltage in the secondary does not show what is happening within the power transformer.? The primary current causes the magnetic field and that field induces a secondary voltage.? That is all you know at this time. ? Then there is the issue of running the power transformer at a greatly reduced voltage which will prevent the current from getting anywhere near to what is needed to saturate the the core and stress the power transformer.?? ? Finally there is the question of fully loading the power transformer to near the design power level.? This should further stress the power transformer and change the voltage-current waveforms to the point where they are obviously distorted. ? From: ? In a purely inductive circuit, the phase relationship between the current and voltage is such that the current lags behind the voltage by 90 degrees. This means that the current waveform reaches its maximum value 1/4 of a cycle (or 90 degrees) after the voltage waveform reaches its maximum value. This lag in the current is due to the fact that inductors resist changes in current, and so the current takes time to build up as the voltage is applied across the inductor. This phase relationship can be seen by analyzing the phasor diagram of the circuit, where the voltage is represented by a vector that is 90 degrees ahead of the current vector. The magnitude of the current vector is proportional to the magnitude of the voltage vector divided by the inductive reactance of the inductor (X_L = 2¦ÐfL), where f is the frequency of the AC voltage and L is the inductance of the inductor. Even when you add the effects of circuit resistance, this relationship is still quite close to 90 degrees. Regards, Jim
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
¿ªÔÆÌåÓýHi jim I think many and me/I would agree with paragraph 2, and 3, but on pgf 1, with all due respect, this is a transformer, and it has some ?resistive load which is reflected to the primary as-in phase current, and likely[must] dominate ?the steady state currents and the current at turn on. If these loads were not there we would see the magnetizing current [as you suggest I think], as transients and as steady state, and ?it would be interesting to know these too, even under low voltage. ?The fact that you/I can barely see and phase shift between voltage and current, proves the large dominance of the resistive load over magnetizing current. Sorry jim, I would not want to see Halden derailed by pgf 1 , but I hope you reconsider it, taking everything into account. My comment is well meaning, though It might not sound like that s, my fingers have deteriorated into hunt and peck with mostly errors, so there is a lot of hysteresis going on here, or reactive power. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, August 4, 2024 7:38 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Halden And that is the problem, there should be a phase difference between the two if you measure voltage and current in the same winding.? Measuring current in the primary and voltage in the secondary does not show what is happening within the power transformer.? The primary current causes the magnetic field and that field induces a secondary voltage.? That is all you know at this time. ? Then there is the issue of running the power transformer at a greatly reduced voltage which will prevent the current from getting anywhere near to what is needed to saturate the the core and stress the power transformer.?? ? Finally there is the question of fully loading the power transformer to near the design power level.? This should further stress the power transformer and change the voltage-current waveforms to the point where they are obviously distorted. ? From: ? In a purely inductive circuit, the phase relationship between the current and voltage is such that the current lags behind the voltage by 90 degrees. This means that the current waveform reaches its maximum value 1/4 of a cycle (or 90 degrees) after the voltage waveform reaches its maximum value. This lag in the current is due to the fact that inductors resist changes in current, and so the current takes time to build up as the voltage is applied across the inductor. This phase relationship can be seen by analyzing the phasor diagram of the circuit, where the voltage is represented by a vector that is 90 degrees ahead of the current vector. The magnitude of the current vector is proportional to the magnitude of the voltage vector divided by the inductive reactance of the inductor (X_L = 2¦ÐfL), where f is the frequency of the AC voltage and L is the inductance of the inductor. Even when you add the effects of circuit resistance, this relationship is still quite close to 90 degrees. Regards, Jim
? _._,_._,_ -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
¿ªÔÆÌåÓýRobert, Halden , ?and all , at the risk of ¡°¡±¡°massively exceeding my bandwidth¡±¡±¡± and being ousted !! Robert, yes, I agree, and I think this was understood, as Halden said he did not want to hit this failed 5 v to HV transformer with much and didn¡¯t want the 800-800 nominal volts ,, oh maybe he said this? , But I for one have been keeping this in my back pocket, waiting for real tests, but even these are interesting. I want to see what he gets out of this one before, taking it up to see where and when the insulation ¡°glows¡± and crackels or whatever. I think I instigated some tests before a real physical autopsy ??so we can know more about the common failures ? From: [email protected] [mailto:[email protected]] On Behalf Of robert meadows
Sent: Sunday, August 4, 2024 4:39 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Halden, I understand that you are not running this transformer at rated input voltage.? Have you not considered that you do not have the design rated magnetic field being generated and therefore, none of your measurements or assumptions can be correct, unless of course you have the transformer design specifications and you have calculated from those specifications the result of a lower voltage on the transformer¡. But, then, the math for that is quite difficult, as well as very assumptive as it gets into lots of transformer design. Cheers, Robert W4RRD EE
-- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden And that is the problem, there should be a phase difference between the two if you measure voltage and current in the same winding.? Measuring current in the primary and voltage in the secondary does not show what is happening within the power transformer.? The primary current causes the magnetic field and that field induces a secondary voltage.? That is all you know at this time. Then there is the issue of running the power transformer at a greatly reduced voltage which will prevent the current from getting anywhere near to what is needed to saturate the the core and stress the power transformer.?? Finally there is the question of fully loading the power transformer to near the design power level.? This should further stress the power transformer and change the voltage-current waveforms to the point where they are obviously distorted. From: In a purely inductive circuit, the phase relationship between the current and voltage is such that the current lags behind the voltage by 90 degrees. This means that the current waveform reaches its maximum value 1/4 of a cycle (or 90 degrees) after the voltage waveform reaches its maximum value. This lag in the current is due to the fact that inductors resist changes in current, and so the current takes time to build up as the voltage is applied across the inductor. This phase relationship can be seen by analyzing the phasor diagram of the circuit, where the voltage is represented by a vector that is 90 degrees ahead of the current vector. The magnitude of the current vector is proportional to the magnitude of the voltage vector divided by the inductive reactance of the inductor (X_L = 2¦ÐfL), where f is the frequency of the AC voltage and L is the inductance of the inductor. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, August 4, 2024 at 02:42:29 PM CDT, HF via groups.io <incorridge@...> wrote:
Hi Jim,
No, I haven't crushed that resistor to inspect it nor measured its inductance.
I have attached a screenshot that shows that there is very little phase difference between primary current and secondary voltage.
Cheers,
Halden VE7UTS
Hald
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
¿ªÔÆÌåÓýRE ???Don, I think you were onto something.?? Halden, you have gone to a lot of work for us¡ªthanks! It takes me a lot of time to digest all this! so I can¡¯t just bounce it back. I have inserted some bare thoughts in green based on what I think you mean. My nit-picking is only intended to clarify and suggest altered thinking, and I hope is seen as helpful and friendly. ? I made a few changes to the setup since the previous session.?? I used to have just one of the low-voltage secondaries loaded.? Now, the 6.3 V secondary is loaded with 0.2 ohms and both 5V secondaries are loaded with 1 ohm.? This causes the currents in these windings to be about what they would be in normal operation.? --- I¡¯m not sure what your intent is, but if you are trying to simulate a cold start, the tungsten heaters and filaments, will be very current hungry, for a few cycles, but it probably won¡¯t alter much?. I¡¯m still energizing the transformer with the 31 Vrms source.? ?¡. 31V / 115V = 27% of normal voltage? ? I inverted the current waveform to make it easier to see the phase relationship with the voltage on part of the HV secondary.? I¡¯m still using the Omron G3MB-202P SSR to turn the power on and off. It turns out that if the transformer ends a cycle with one polarity and starts the next cycle with the same polarity, the current on one side of the AC cycle starts out higher than usual in most trials.? ¡.was anticipated I think ? ? The magnitude of the extra current varies. But if it ends on one polarity and re-starts on the other, it operates normally.?? ¡ ?normally = lower inrush? ? Example images 14 (opposite) and 17, 19 [13?] (same) illustrate this.? Image 27 shows how the extra current decays over several cycles.??? I see 14,13?? --?? 17, 27??? -- 63?? ¡.? Your 19? = is really [13]?, I will assume for now. And so we gather that restarting with the same voltage polarity as the last turn off generates noticeable inrush current?? ¡ as anticipated I think ? To investigate further, I tried to pre-magnetize the core by applying power through a diode just before a turn-on test.? Afterwards, turn-ons with one initial polarity gave extra current while turn-ons with the other polarity looked normal.? Image 63 shows one case where not only did current increase on one side of the cycle, but it also decreased on the other side of the cycle. ¡ the way I look at it is that this shot shows a very little AC inrush due to saturation, but a significant DC offset, which is generally expected from zero voltage switching for any inductor or transformer, but it is surprising that the DC offset lasts that long in this small transformer. See my attached marked-up version of #63?????? ,, I see no DC offset in 14,? but? DC offset is evident in all the others including 17?? ? But at no time during these experiments did I see a voltage spike.? This only serves to show the magnitude and nature of excess current that can flow due to remanance in this transformer.? Yes The primary current during these tests was about 0.7 A rms.? Actual current when not transmitting is about 1.4A rms.? Thus, the transformer magnetization would be about double in actual use relative to the conditions of this test.? ¡ well, if the current change is due to higher input voltage ¡yes ,double of more due to saturation, ¡.but if it is more load and the same low input voltage,, well.. in my understanding, the normal AC magnetization in an inductor or transformer depends on the voltage. In a transformer the very tight feedback of ¡°secondary flux¡± neutralizes 99% of the ¡°primary flux¡± so the net flux barely changes, so it might depend on some details ot the assumptions. ? Thus, the surge current would be at least the fraction shown here [Image 63] and possibly a little more.? ¡ Yes? perhaps for an ideal transformer, but a real transformer will likely saturate under normal voltage start, but not under half voltage start, so ¡ depends It¡¯s not likely to be much more than double because the transformer is designed to transform twice again as much power when transmitting at full tilt and should not saturate at that time.?? ?¡? likely cant reenergize transformer under full power?? ? ? Using an SSR at turn-on does not enable one to select whether the polarity at turn-on will be the same polarity as it was at the prior turn-off.? Use of an SSR or TRIAC at turn-off might even maximize the remanence in the transformer by ensuring that it has a full half-cycle of current at one polarity just before power is removed.? ¡¡I expect this too, but when it comes to mechanical switches, some not fast, have a minimal throw, and minimal arc, and just wait for current zero, while some are very fast have a big throw, and long arc? so that under light load they can snuff the energy/current in mid cycle. I have always wondered just what happens in all these various ¡°switches¡± ? But it might be more gentle on the transformer by avoiding multiple on-off cycles during turn-on using a switch with mechanical bounce.? ¡.yes? but an aside, we now find lots about this, but it is switching into a very light load for logic, we saw lots of it back in 1960¡¯s.70¡¯s +? .. just how high and fast were these bounces?.. it takes only a smidgeon of a gap to break a few volts resistive and see every bounce, but if one tries to make and break 120 volts at 1 amp fairly inductive might not be so simple, and probably has many answers , maybe you will see. ?? ? ====EEEEEEEEEEEEEEEEEEEEE? ? From: [email protected] [mailto:[email protected]] On Behalf Of HF via groups.io
Sent: Sunday, August 4, 2024 2:25 AM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Don, I think you were onto something.? ? -- don??? va3drl |
Jim Whartenby
don Root