[HN Gopher] Practical Transformer Winding (2010)
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Practical Transformer Winding (2010)
Author : bearbin
Score : 108 points
Date : 2021-12-25 17:50 UTC (2 days ago)
(HTM) web link (ludens.cl)
(TXT) w3m dump (ludens.cl)
| Animats wrote:
| That's so retro. Useful if repairing boat-anchor equipment from
| the 1950s.
|
| Here's a more modern video on winding toroids by hand.[1]
|
| [1] https://youtu.be/sDIWNHOoNh8
| londons_explore wrote:
| Nearly all usecases for a power transformer are now better served
| by a switched mode power supply.
|
| They tend to be much smaller, lighter, more efficient, cooler and
| cheaper. They also have features like adjustable output voltage,
| current limits, and overheat protection. Some can input and
| output AC or DC, at a configurable frequency and sometimes
| waveform. Some offer the same galvanic isolation that a
| transformer offers too.
|
| The core of a switched mode supply usually _is_ a transformer, or
| at least an inductor, but the key difference is that it operates
| at far higher frequencies than classic uses of transformers,
| which allows them to be far far smaller, and therefore cheaper
| for the same power output.
| snowwindwaves wrote:
| Are you saying large Transformers 1 mva, 10 mva, 100 mva, 500
| mva are obsolete and should be replaced by switched mode power
| supplies? What mva is the threshold?
| londons_explore wrote:
| For new installation, yes, for any size a switched mode
| supply will usually be better in all dimensions. For the
| largest sizes, you can't buy them off the shelf, and there
| design costs may dominate. But after the thing is designed,
| in component costs, switched mode will win. Everything scales
| linearly with kVA, so there is no economics crossover point
| for the fundamental materials.
|
| Eventually it will be worth switching out old transformers -
| they contain a massive amount of valuable copper and quite
| valuable steel, and their lower efficiency means every year
| they remain in service they are wasting $$$'s of electricity.
|
| Transformers in cities can often be replaced with much
| smaller switched mode units underground, allowing the
| building housing the old transformer to be rebuilt as luxury
| flats to make the project much more profitable too!
| snowwindwaves wrote:
| Large power transformers have efficiencies in the 98-99.75%
| range.
|
| I don't doubt switch mode could be smaller and cheaper up
| to some size, but I am struggling to see transformers
| larger than about 5 mva being replaced with power
| electronics.
|
| Solar farms etc have inverters in modules I believe 500 kva
| each - and of course the power electronics are necessary
| there, there is no substitute.
|
| I have a 20 MVA transformer that is nearly at end of life
| and would be open to cheaper replacements.
| wglb wrote:
| Those properties are all positive, but there is one glaring
| negative: rf radiation. I know some ham radio station builders
| that will not allow any switched mode power supply on their
| property, including wall warts and smartphone chargers.
| Animats wrote:
| That's a problem, especially with low-end power supplies.
|
| I designed a switching power supply a few years ago for a
| specialist application - driving 1930s Teletype machines
| which need 120VDC 60mA.[1] A switching power supply is a
| spike generator. Here's the schematic.[2]
|
| This is reasonably RF-quiet. The transformer of the switching
| power supply is a toroid in a metal can, so you don't get too
| much RF from the transformer itself. But that's not where it
| usually comes from. The important thing is to keep spikes out
| of both the input and output wiring. That's dealt with by
| using LTSpice to simulate the circuit, and adding small
| capacitors and inductors until the spikes have disappeared in
| both voltage and current. At the output end, note the snubber
| C7, R1, D10, and D11, to soak up any spikes from the
| inductive load, and L2, to soak up output side current
| spikes. There's L1 and C12, to soak up kickback from the
| switched input side of the power supply. Plus C10 at the
| power input, which is from a USB port. They're all tiny
| surface mount components. The inductors are ferrite beads in
| surface mount form.
|
| So there are eight extra components, just to prevent unwanted
| RF generation. The LTSpice simulation shows that they're all
| needed. The simulation was used to choose the values.
|
| This is why good switching power supplies have more parts
| than bad ones. You see that in teardown videos.
|
| [1] https://github.com/John-Nagle/ttyloopdriver
|
| [2] https://github.com/John-
| Nagle/ttyloopdriver/blob/master/boar...
| aivisol wrote:
| Winding your own transformer was one of those things which amazed
| me as a teenager: you do a simple math by calculating winding
| ratio and the voltage is changed at the secondary by magic...
| myself248 wrote:
| Yesss! This is what I was hoping to find last time I clicked on
| an HN headline "transformers from scratch", which turned out to
| be about machine learning:
| https://news.ycombinator.com/item?id=29280909
|
| This is great. It gets into the flux density and iron loss
| calculations that affect the physical size of a transformer core,
| choosing the wire, and then exquisite detail of actually winding
| and finishing the thing.
|
| I need to spend a bunch more time reading this site.
| belter wrote:
| The Transformer Winding community knows that you won't let us
| down.
| scoot wrote:
| A transformer and coil design guide from the same author:
| https://ludens.cl/Electron/Magnet.html
| formerly_proven wrote:
| I find this trend of naming software ideas after common words
| really quite annoying (transformers, lenses, optics etc.)...
| myself248 wrote:
| Or using the word "bandwidth" to refer to "capacity" or "data
| throughput" rather than "the width of the band that the
| signal occupies". Arrrrgh. Yes the two things are the same
| for certain naive modulations, but the whole point of using a
| better modulation is that you get more throughput for the
| same bandwidth. Understanding this requires first unlearning
| the abuse of the term, and that's hard work for a lot of
| engineers who really need to understand this.
| jbay808 wrote:
| Shannon's channel theorem states that the information
| capacity of a channel is directly related to the bandwidth
| and the signal-to-noise ratio, even if you use the best
| possible modulation scheme:
|
| https://en.m.wikipedia.org/wiki/Shannon%E2%80%93Hartley_the
| o...
| p1esk wrote:
| He's talking about throughput, not the information
| capacity of the channel.
| jbay808 wrote:
| Can you explain the difference? They seem to me like
| virtually the same concept, but you seem to see an
| important distinction.
| p1esk wrote:
| Channel capacity is an ideal theoretical concept
| establishing a maximum data transmission rate over a
| channel with strong assumptions about the noise in that
| channel. Throughput is what you actually get in the real
| world, and it depends on many things, including a
| modulation scheme, retransmission protocols, specific
| noise models, etc.
| analog31 wrote:
| From what I've read, that's why physicists started giving
| things whimsical names like Quark, Charm, Strangeness, etc.
| The problem with using common words is that they always
| suggest an analogy, the analogy is never perfect, and often
| causes more confusion than understanding.
|
| (Also, Murray Gell-Mann was a whimsical character to begin
| with).
| amelius wrote:
| Or naming companies after physical units (e.g. Tesla).
| codingdave wrote:
| Or naming physical units after people (e.g. Tesla).
|
| FWIW, Tesla the company was named after Tesla the person,
| not the measurement.
| dylan604 wrote:
| Yeah, the comment you replied is almost troll-like
| amelius wrote:
| Why? Many professionals use the unit Tesla on a daily
| basis. It's like someone claiming the word Pixel for
| their company or product which I'm sure already happened.
| formerly_proven wrote:
| https://store.google.com/category/phones
| bob1029 wrote:
| I agree, but at the same time "Sequence-to-sequence model
| utilizing self-attention" doesn't roll off the tongue as well
| and would otherwise make the thing more difficult to talk
| about.
| priansh wrote:
| Touche, I opened this hoping to find a new method to train
| Transformers and got the opposite
| GnarfGnarf wrote:
| I ran a high school science lab in Bolivia in 1968. It was
| cheaper to get a local guy to _hand-wind_ forty centre-tap
| transformers, than to order them from Germany or the U.S.
| hwillis wrote:
| Ludens is absolutely legendary. This is part of his micro
| hydroelectric dam[1], which he uses to power his house, which he
| of course built himself.
|
| Far different, but if you enjoyed this you may also enjoy another
| classic (which does not have explanation), Claude Paillard making
| a vacuum tube from glass and metal:
| https://www.youtube.com/watch?v=EzyXMEpq4qw
|
| [1]: https://ludens.cl/paradise/turbine/turbine.html
| willis936 wrote:
| Incredible. I had a dream when I was a child of a house powered
| by small-scale hydroelectric, but learning the reality of water
| rights made me abandon it. It is truly inspiring to see someone
| live this dream.
| bserge wrote:
| VBprogrammer wrote:
| There are interesting people on thebackshed.net who have been
| building whole house inverters, initially repurposing some
| Chinese inverter chip but more recently an arduino for the
| brains. Unfortunately a lot of the info is spread across many
| different build threads but a big part of it is about rewinding
| toroidal transformers.
| Isamu wrote:
| > Transformer steel is not all born alike. Manufacturers will
| provide data sheets about their products (often on their web
| sites), where you can see what they offer. There are usually many
| grades, with vastly different loss characteristics. At a given
| flux density and frequency, a good material might have ten times
| less loss than a cheap material! So it pays to look, investigate,
| and decide intelligently what to buy. Thinner sheets normally
| have lower loss, and the rest of the secret lies in the exact
| alloy.
|
| Okay this is what I come to HN for, thanks everybody!
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