in the 1980 Audio Magazine, Walter Jung published an article about building an energy bank, that was a good sell that started a trend and those computer caps found a new use.....
i emailed WJ some years back for permission to post his article here in our boards but he told me, he had a change of heart and does not recommend it any longer....
after all these years when his article has been embraced by a lot of diy'ers, me included...
now it is in the public domain here.....https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1980-08.pdf
no i did not, if you have them you can post them...
i guess at turn on there is some transient currents that happens, but for small transformers like the ones used in our amps, i do not worry...
prior to 1980, this turn on issues was non existent...
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easy to answer, first they can afford to buy it, second, because they want it, enough reason to them...
i would if i could.....
today supercapacitors are used in cars in lieu of the 12volt battery...Replacing My Car Battery with Capacitors! 12V BoostPack Update - YouTube
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TonyTecson, you referenced a 2.5kVA power transformer - that is the same VA rating as the OP has indicated for this thread, and certainly not a 'small' transformer in the context of a domestic setting. Although your PT wouldn't have been a toroid (I assume), it would have been informative to see an actual set of test results given you say you use a special design.
I don't test amp traffo's more than about 300VA at home, and use 240VAC, so the dynamics are quite different for me. I have a LEM set up for testing AC current, but it clips at 8Apk (which easily happens with a 900VA isolation transformer I rarely use). Inrush is not a simple measurement to make if you don't have a special analyser instrument for that test, and can be quite influenced by the impedance of the AC feed and the voltage.
I don't test amp traffo's more than about 300VA at home, and use 240VAC, so the dynamics are quite different for me. I have a LEM set up for testing AC current, but it clips at 8Apk (which easily happens with a 900VA isolation transformer I rarely use). Inrush is not a simple measurement to make if you don't have a special analyser instrument for that test, and can be quite influenced by the impedance of the AC feed and the voltage.
there is nothing special about my designs, just common sense, running my traffos below 1T even if they are good quality cores, 0.35mm instead of 0.5mm, rm18 or m24 grade instead of the more common and cheap H50, although m6 would have been ideal, it would have been very expensive here...
no, i am not inclined on using toroids....
no, i am not inclined on using toroids....
The relevant pages on a capacitor bank are missing from this, Tony! Only page 48 with the conclusion is there.
Tony, for example, I was educated at university in the energy department in the field of industrial electronics. You cannot even imagine what equipment we design for substations and power plants and what aces-developers work next to me. Many have advanced degrees. I posted these links from the toroidal transformers manufacturer's website. I also design transformers myself. You cannot wind more turns of wire around the magnetic circuit against the calculated values, only to reduce the starting current.
РЗА подстанций ПАО <<Россети>> 6-750 кВ
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I agree with Tony that even a 2.5 kVA transformer used in an amplifier is unlikely to see a high enough inrush current to blow the fuse in the amplifier, and it probably wouldn't trip a breaker either. It could, however, be pretty hard on the contacts in the power switch.
In some situations, it is possible to take advantage of this to squeeze a little more out of a pulse transformer before saturation than would otherwise be possible.
In some situations, it is possible to take advantage of this to squeeze a little more out of a pulse transformer before saturation than would otherwise be possible.
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The way I've always done it for big transformers is with a Rogowski coil or Pearson current transformer, then using the single shot capture on a DSO. Keep in mind that Rogowski coils also need an integrator.
I'm struggling to come up with a cost-effective way for someone to do this in their basement, however. TBH, any time a transformer this big is employed in an audio circuit the filter caps are big enough that a soft-start circuit is necessary regardless.
FWIW, if the OP is going to have half a farad of filter caps at 95V (realistically twice that, since it will have +/- 95V rails), they need to be considering the use of some far more sophisticated protection circuits than we have been talking about here. I would not feel comfortable troubleshooting something like that live the way we typically troubleshoot amplifiers. In fact, I wouldn't even feel comfortable powering it up with the chassis open unless I was behind a lexan shield (preferably with some distance as well). 2.25 kJ is enough to cause serious injury beyond the usual concerns about electric shock. If semiconductors fail, they will be vaporized, package included. Good chance the PCB will be totaled, and I wouldn't rule out severe damage to other things inside the chassis.
You can rest assured that this will carbonize the switch and socket contacts the first time.
In general, if you want to make a high-end transformer, then you should all strive to reduce losses in it, and not vice versa, achieve a decrease in starting current with a ridiculous result of 10-15%.
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I just want to explain transient mode when we energize a primary winding. Everithing go different at that moment.
No, you can use more turns to decrease it. I've done easy experiment with a variac and AC ammeter, and I see that:
When induction goes lower 1.4-1.5 times from maximum possible for that core material - inrush current goes lower (that is 150-160VAC applied to 230 VAC rated primary).
When induction is 2.0 times lower then maximum - inrush current goes even more lower. (110-115 VAC applied to 230 VAC raten one). And additional wire resistance helps with it.
I can't say exact numbers but difference is up to about several times for each step above.
As I suspected previously, TonyTecson uses low induction (about 1T as he say) and not toroid core type, so thats why he usually doesn't meet a problem with high inrush current (as it is in usual transformers). But if he was more curious about it - he'll found that inrush current always is higher then in set mode.
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This is the wrong approach. In this case, you will lose power, material consumption, cost and, most importantly, you will lose in efficiency of the transformer. I do not care about the starting current, this problem has always been solved elementary. But as a developer, I am always worried about the efficiency of a transformer, its dimensions, weight, labor costs and the final cost.
No, it is better to say there isn't "a wrong approach", but there is a different intention or a different goal. As you understand, we don't talk here about 6-750 kV rated power transformers.
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The toroidal transformer I designed and manufactured at the factory had a power of 3.9 kW, a weight of 18 kg and a primary no-load current of 60 mA at 245 V. This is already too good a quality indicator. There is nothing to improve in it except weight and price.
When tested without thermistors, the fuses could not withstand the inrush current at all when connected to mains. During the tests, as usual, we turned it on through a laboratory autotransformer with smooth control.
How can you reduce the starting current in it? Would you like to wind even more turns?
When tested without thermistors, the fuses could not withstand the inrush current at all when connected to mains. During the tests, as usual, we turned it on through a laboratory autotransformer with smooth control.
How can you reduce the starting current in it? Would you like to wind even more turns?
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ok, that was my impression too...transients do not last long, 5 cycles is long enough, but in some cases long enough to weld switch contacts....everything has a context....
Just wanted to say that I have an older project that uses a 1.5kw toroid with no soft start. I think the capacitance is like 333,000 per rail. I forget the model switch, but it's just a common industrial switch rated at probably 15-20A. It's a solid click you get from it and the lights blink momentarily, but I am totally confident in it. I think I foil wrapped the fuse though, I don't remember lol. Dont use it anymore
A side note, I would think that you could also run a couple thermistors in parallel with the chassis resistor. The thermistors would take over for where the chassis resistor leaves off in the event of a failure.
A side note, I would think that you could also run a couple thermistors in parallel with the chassis resistor. The thermistors would take over for where the chassis resistor leaves off in the event of a failure.
A while back, a customer brought his large flatscreen TV into my shop for repairs.
He sat it on the front counter, face down, and as I was writing up his claim check to jot down the model number, I noticed several screws were missing from the rear cover.
I know full well from decades of servicing, that no manufacturer sells a TV that way.
I questioned him about it, and his reply was "I don't know why".
Later that week, when I got the TV up on the bench, took the cover off, and the first thing that I spotted was the 5 amp fuse wrapped in several layers of tinfoil.
Along with that, blackened circuit boards.
I went no further, I called the customer and asked him to haul that mess out of my shop.
This is typical of stupid people with the idea that if they "force juice" into something by disabling or increasing the fuse rating, they "might" get the thing to work.
My thoughts are, if it blows a fuse, find out why, and remedy the issue correctly, and safely, don't attempt to push your luck, or keep replacing the fuse.
Because each time a new fuse blows, something else is likely destroyed, making more of a mess to repair.
"This message was brought to you by a certified electronics service technition"
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