Locked Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
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Don I was responding to what you said which is at the very bottom of this email. "Anyhow, Halden¡¯s current was about in-phase with the voltage [ I copied and shifted the current which is not perfectly symmetrical, but was not able come up with any shift ], so the load current was determining the ?primary current ?no matter how meaningless you think it is." There is no need to correct anything.? If anyone is still following this thread, the point has been made that there is a phase difference between I&E in a reactance.? In fact, this is the very meaning of the word "reactance."? ? But to see this clearly, both have to be measured at the same time and place.? Measuring I in one transformer winding and voltage in another will not show this special relationship. I look at this forum as a means to share knowledge about these fine radios.? I understand that some of us come to this forum without a solid understanding of component fundamentals and that is OK.? It is not really necessary to go into the technical weeds when one already realizes that old waxed paper & foil capacitors should be replaced, even before one applies AC power.? Tubes should be checked for emission and shorts and while cleaning the chassis, look for signs of damage.? Always check any fuses for the proper value! Just keep in mind that these radios were designed and built with an eye on cost.? The best components were too expensive to use.? That is not to say that hallicrafters radios did not perform well, they certainly did but comparisons have to be made with other radios in the same price class.? It should go without saying that a radio of the same era costing 10 times the price should perform better. One last thing, don't be afraid of challenging "common knowledge."? There is a lot out there that is considered "undeniable facts" but which falls apart when one takes a closer look. Back to fixing up nice old radios, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Wednesday, August 7, 2024 at 12:03:24 PM CDT, don Root <drootofallevil@...> wrote:
Hi Jim,? You are right about needing to get into the nitty-gritty! I don¡¯t understand why you wrote all this, but it¡¯s good to learn more, thanks. but at the end you said: ¡°If you can find a source that backs up ???¡.???? your claim that voltage and current are in phase in reactive circuits,¡¡..¡± I took a lot of time looking for that phrase in this thread even going back 100 postings, and even using Ctrl-F, and then even looking for a three word sequence, and I can find nothing in this topic. So, maybe I was sleepwalking when I posted it or sleepwalking when I deleted the posting. So please advise what the message number is, so I can edit it, correct it and apologize to members that I have deceived, all in the interest of group integrity. ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Tuesday, August 6, 2024 2:01 AM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Don The transformer has many inventors, as you may know, if you have done any research on the subject.? Much of what was used to electrify Niagara Falls came from Europe since they were far ahead of Westinghouse in AC development at that time.? Tesla became a hindrance to Westinghouse in three phase power development.? Tesla's polyphase system is not the same as a three phase system.? But this is another story. ? Induction is the key to the operation of chokes, transformers, motors and anything else that uses a coil of wire.? A transformer is just two or more inductors that are magnetically coupled and share the same magnetic flux but the basic operation is the same as an inductor.?? ? In an inductor, as the magnetic flux builds, it cuts the same coil and produces a counter electromotive force (EMF) to oppose the current that is producing the magnetic flux.? If DC current is producing the magnetic flux, the flux will reach a maximum density since the steady state current cannot produce any more magnetic lines of force so induction stops.? If AC current is producing the magnetic flux, it again reaches a maximum but then changes direction and reverses back to zero current then changes the direction of the magnetic field to repeat the process with an negative current.? Induction does not stop when AC current is involved. ? So induction is producing a second current in the same coil to oppose the buildup of the magnetic field and force a constant current to flow.? If a second inductor also sees this same changing magnetic flux, a second EMF is produced in this second inductor.? If the number of turns in each inductor is the same, the same voltage and current appears in the second inductor.? Increasing the number of turns in the second inductor increases the voltage but reduces the current so the same power is available in the second inductor or winding.? Reducing the number of turns in the second inductor reduces the voltage but increases the current.? The power induced in the second inductor or winding is the same as that found in the first inductor or winding less any power loss in the wire and magnetic core. ? As for the voltage and current being in phase in inductive circuits, it is just not possible.? See: In part: "The phase difference between voltage and current in an AC (Alternating Current) circuit is due to the presence of reactive components, such as capacitors and inductors. In a purely resistive circuit, the voltage and current are in phase, meaning they reach their maximum and minimum values at the same time. However, in circuits with capacitive or inductive elements, the voltage and current exhibit a phase difference. In a capacitive circuit, the current leads the voltage by 90 degrees. This is because the capacitor opposes changes in voltage, causing the current to reach its maximum value before the voltage reaches its maximum. In an inductive circuit, the current lags the voltage by 90 degrees. This is because the inductor opposes changes in current, causing the voltage to reach its maximum value before the current reaches its maximum. The phase difference between voltage and current has important implications in the analysis and design of AC circuits, as it affects the power factor, which is the ratio of the real power to the apparent power. A phase difference other than 0 degrees results in a power factor less than 1, which can lead to inefficiencies in the circuit." There is more in the above article but this will suffice. ? I know that all of this is confusing and contradicts what you may have learned in tech school if you have had some formal training in electronics.? Shortcuts in explaining what happens in reactive circuits were made so as to cover as much ground as possible in a relatively short time of study. When you do a much deeper dive, you will find that these shortcut explanations no longer explain what is happening.? They just don't hold up.?? ? If you can find a source that backs up your claim that voltage and current are in phase in reactive circuits, please post the URL here, I would be interested in what it has to say. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? On Monday, August 5, 2024 at 09:40:06 PM CDT, don Root <drootofallevil@...> wrote: ? ? Thanks for responding Jim You could have a transformer with such bad steel that the magnetizing current dominates the reflected current from the load, but nobody wants one of those. I don¡¯t know if somehow we are talking past each other somehow bu Mr Faraday was working with induction coils ¡°When was the transformer invented? A: The property of induction was discovered in the 1830's but it wasn't until 1886 that , working for Westinghouse built the first reliable commercial transformer.¡± ? Anyhow, Halden¡¯s current was about in-phase with the voltage [ I copied and shifted the current which is not perfectly symmetrical, but was not able come up with any shift ], so the load current was determining the ?primary current ?no matter how meaningless you think it is. ? -- don??? va3drl |
Jim Whartenby