How electric trains work and why they make interesting sounds [video]

210 pointsposted 2 months ago
by zdw
(youtube.com)

78 Comments

jkingsman

a month ago

Fascinating video! One of my favorite train vids is a Taurus starting up in frigid conditions. As the wheels slip and the PWM modulation on the individual motors varies to keep traction, it makes beautiful music.

https://www.youtube.com/watch?v=Q_bF1Wb_pSE

asciii

a month ago

That's really neat - it sounds like a violin. I can barely keep a tune so I'm wondering if anyone knows anything special about the melody

rob74

a month ago

Detailed explanation (in German) here: https://de.wikipedia.org/wiki/Siemens_ES64U2#Ger%C3%A4uschen...

> Google translation: When switching on from a standing start, a noise can be heard that is reminiscent of playing through a scale on a tenor saxophone. It is created in the three-phase motors by controlling the power converters. The noise is twice the clock frequency of the pulse inverters, which is gradually increased. The frequency changes in whole and semitone steps over two octaves from d to d" in the tone pool of the root tones. It is a Dorian scale on the root D. Theoretically, it would be possible to program the locomotive in such a way that it emits completely different sounds. However, the manufacturer has opted for a scale because these sounds are perceived as pleasant by the human ear. This makes it possible for a four-voice tone to result when the wheelsets are spinning (for example due to wet rails).

No wonder the Austrians (who have a reputation of being music lovers) have most of these engines...

asciii

a month ago

Wow! I love HN for these finds, thank you

bmicraft

a month ago

Well, those VVVF frequency converters were specifically tuned to have their "steps" on full notes/chords. It doesn't sound like that by accident.

gorlilla

a month ago

They sound just like stepper motors to me. Especially when they're operating to create a radius/arc in a 2-D plane.

user

a month ago

[deleted]

theideaofcoffee

a month ago

As much as I love the futuristic and sophisticated sounds that electric traction drives make as compared to their fossil-fueled counterparts, I do think that the driving and control systems that actually generate the PWM waveforms that are sent to the motors are even more interesting. Huge, massive IGBTs weighing a kilo+ each chopping up hundreds of thousands of joules/s of energy without destroying themselves, current transformers, contactors, it really tickles parts of my brain. He only spent a handful of seconds on those, would be interesting to hear a deeper dive.

rwmj

a month ago

Photo on Wikipedia:

https://en.wikipedia.org/wiki/Insulated-gate_bipolar_transis...

Are they manufactured using regular silicon lithography? You'd think when making something so large you could just mix up the chemicals instead.

rcxdude

a month ago

It's definitely lithography on silicon wafers, but a lot of the details are very different. For example, it's pretty common for power devices to be manufactured to be formed from the full thickness of the wafer, as opposed to just on the surface. And a single device tends to be formed of many repeating blocks, since you do need fine details still to get the performance (And a lot of the challenge is making sure each of those blocks is as similar as possible, so you don't get hot-spots).

(silicon lithography is more of a broad range of processes: digital vs analog vs power vs MEMS all have very different needs, and so a process designed for one will look very different to another, and one designed to allow multiple will be making compromises)

namibj

a month ago

The "full thickness" aspect is commonly called "vertical" when talking about the devices.

Animats

a month ago

It's amazing how small those things are. That's a transistor which can switch four megawatts. A manual switch with the same rating is bigger.

Here's a data sheet for a somewhat larger one.[1] The control signal is only 6 volts at 5 mA. It's incredible that this is physically possible.

[1] https://www.infineon.com/dgdl/Infineon-FZ1500R45KL3_B5-DataS...

leoedin

a month ago

As an embedded engineer sometimes working on PWM, it's interesting to think that the origin of the gate drive signals is still just some sort of microcontroller timer running at 3.3V and a few mA. I'm sure there's a few layers of level translation and isolation between the micro and the 4 MW power transistor - but it's still indistinguishable at the digital level from a circuit driving a tiny motor on my desk.

0_____0

a month ago

An ant driving an M1 Abrams main battle tank.

theideaofcoffee

a month ago

From what I understand, mostly yes. They are still built up layer-by-layer with standard litho techniques, with pattern masks, ion implantation for the p- and n-type layers, etching, CVD to deposit insulation material (for the 'insulated gate' part of the device). Though they don't have to be nearly as precise, as I understand it as something more sophisticated, like a cpu, they still need to lean on those to make it chooch.

bgnn

a month ago

I don't thik they're produced with the same process as CMOS, but I bet some photolithography is involved.

1970-01-01

a month ago

Very early EVs (GM's EV1 and then a few other GMs) used banks and banks of water cooled IGBTs to spin the motor.

itishappy

a month ago

Same! That stuff is so freakin' interesting! The other deep dive I really want (pun intended) is submarine sonar transducer drivers, which as I understand do basically the same thing but bidirectional and with a LOT more waveform customization.

exabrial

a month ago

I do not have perfect pitch (cool party trick), but I can identify all 8 'normal' equal temperament intervals by ear relative to a reference (If you couldn't guess, I play bass, which is a lame party trick).

I was in Austria last year, and a bunch of the trains starting from a standstill had a "gradual acceleration" algorithm for their traction motors. As the drive frequency increased, you could hear the drive motor whine (or maybe it was the inverter?) along with the frequency. It was fascinating, because it played chords as it accelerated: root, 2nd minor, 4th major, 6th minor, octave, then it would pause at the octave and do it again after a few seconds until it reached max power I assume. Each chord had a very faint tritone added to it relative to the chord tonic, so you got this really harmonic pulsing.

After the second course there was too much rail noise to hear what happened, but it was fascinating. I'll try to find a video, I know I recorded it.

Power in Austria/Germany is delivered to trains via a really weird standard too: something like 25hz 27 kV. Leftover standard from 100 years ago.

the_mitsuhiko

a month ago

Normally it just plays the scale: https://www.youtube.com/watch?v=-SDYdHzT7Qw

But it can be configured to play other tunes. Here is a rare recording of it playing the Austrian anthem: https://www.youtube.com/watch?v=UkdQmDGU9AM (another recording: https://www.facebook.com/unsereOEBB/videos/290883783832057/)

exabrial

a month ago

That was fascinating! That is different that what I remember hearing but that's exactly what I'm talking about!

Just compared it to a midi player... first video starts on a G. It may not be equal temperament? Some of the scale degrees sound just slightly flat or sharp.

bobthepanda

a month ago

25kv 50/60Hz is the norm.

The German standard you are thinking of is 15kv 16.7Hz.

exabrial

a month ago

Thanks! 16.5hz, wow that’s barely moving voltage

Animats

a month ago

Some OBB locomotives have their PWM systems tuned so that when they change frequency, they're always on a standard musical note. There's one example of that in the video. It's a cute feature, people like it, and it's probably all in software.

0_____0

a month ago

They could easily have picked aharmonic intervals, and it would have even been a little easier. But given the opportunity, they chose to make something that added a little bit of color and magic to the world. I love that.

mlok

a month ago

It's a mystery to me how the camera is mounted for the video at 7:55.

https://youtu.be/IRJIJPTUXXE?t=474

A drone ?

The camera follows the train so precisely that it seems it is mounted on the train, but it passes on the other side of some objects so it cannot be mounted on it.

zdw

a month ago

I think that's game footage, but not sure what game it is. The train game or sim genre has a bunch of folks who go incredibly deep and accurate in their representations of real trains.

If you want an incredibly detailed 3 hour history of the genre: https://www.youtube.com/watch?v=5vwE_p9SCXw

sicross

a month ago

That’s not a real life video. Is a capture from a train simulator app.

Like Microsoft Flight Simulator, but for trains.

Example: https://www.trainsimworld.com/

tshaddox

a month ago

Apt example considering that they also released Microsoft Train Simulator in 2001.

radiowave

a month ago

Your example is the exact answer.

mjamesaustin

a month ago

The secret behind this camera is that it exists within a virtual world, and therefore can freely float anywhere ;)

An easier giveaway might be the floating teal icons on the station platform.

lainga

a month ago

I believe this is an example of ludonarrative dissonance. The camera is simply at a fixed offset from the train model.

rootusrootus

a month ago

Simulations have gotten quite good, apparently. It threw me for a loop for a moment, too, until I figured out what was going on.

jimmaswell

a month ago

I still find it amusing that most fossil fuel trains only burn it to power a generator, with the wheels run by electric motors. It makes perfect sense with the massive startup torque a train requires, something electric motors are much better at.

vvanders

a month ago

Not just torque, traction too.

VFD AC motors will intrinsically self-correct for overspeed when static traction slips and starts going into dynamic region (due to the frequency being slower than the slip/overspeed) and re-enter static friction region. DC or ICE will react to the lack of traction by turning faster as you hit the dynamic friction region and "spin out". Traction control is always reactive and lags behind. Last I read the difference in traction on rail for AC vs DC was on the order of 50%(!).

It's also why EV cars have stupidly awesome traction in adverse conditions under acceleration, trains had been perfecting that technology for decades.

jillesvangurp

a month ago

That's true for a lot of heavy equipment. A lot of ships use diesel generators to power their electric engines. Same for a lot of mining and construction equipment. Likewise, most hydrogen vehicles are basically a fuel cell powering a tiny battery powering an electric motor. Fuel cells aren't great at variable output so it's easier to just put a battery in between.

That also makes fully electrifying these things less off a technical challenge and more of a battery cost challenge. Mostly size and battery density isn't that big of a deal even. There's plenty of room in a large heavy vehicle to put some batteries. Even if they weigh a few tons it's not necessarily that big of a deal. Except of course if you need to go half way across the globe with a ship. But shorter range of up to 100-200 nautical miles if very doable now. A big mining truck has plenty of space and they are big and heavy anyway.

stackghost

a month ago

The term for that is a hybrid series powertrain. It allows one to optimize the generator to run at a single RPM, which leads to efficiency benefits.

rsynnott

a month ago

Some buses also use these. Dublin Bus has a particularly disconcerting plugin hybrid variety; if it’s using the diesel engine, that runs constantly (so it’s noisier than a normal bus at rest) but if on battery, it’s silent. There are few things more unnerving than a double decker bus gliding along virtually noiselessly (their pure-electric buses, somehow, are noisier). Double-decker buses are supposed to sound like they might explode at any moment, like in the good old days.

(/s, just in case; ye olde 20 tonne 1980s buses were extremely noisy, and it was not great.)

drmpeg

a month ago

The other problem it solves is the complex transmission required. Diesel-Hydraulic locomotives were built, but were not successful long term. The most famous is the Krauss-Maffei ML4000, built for the Southern Pacific railroad.

https://en.wikipedia.org/wiki/Krauss-Maffei_ML_4000

euroderf

a month ago

FWIW back in the 80s Mother Earth News had plans for a car that used this principle.

Loughla

a month ago

I genuinely believe hybrid cars will be the path once we get the itch for electric cars out of our system. You get all the good parts of each engine type, with less of the bad parts of the other type.

elihu

a month ago

Continuing to burn fossil fuels forever isn't really an option. At some point we'll effectively run out, but before then we'll have caused catastrophic climate change due to our CO2 emissions.

Synthetic or plant-based fuels are plausible options, but synthetic fuels can't compare with battery EVs in terms of energy efficiency, and plant based fuels need crop land that's probably better used to grow food.

Electric vehicles aren't a temporary fad. They're here to stay. Liquid fuels aren't going away either, but I expect eventually they'll be used mostly for military and aviation applications, not ground transportation.

amluto

a month ago

> synthetic fuels can't compare with battery EVs in terms of energy efficiency,

This is almost meaningless. If you are turning renewable energy sources into either synthetic fuel or grid power, then efficiency is irrelevant. What matters is cost (of the whole system, including distribution of the energy) and emissions (burning even carbon-neutral methane or hydrogen isn’t quite zero emission). There are startups working synthesizing fuels from air and solar energy, and they argue, fairly convincingly, that bypassing the entire electrical distribution network can more than make up for extremely low efficiency.

Also, heavier vehicles likely emit more brake and tire dust than lighter vehicles, and a series hybrid can be much lighter than a long range BEV.

elihu

a month ago

Of course efficiency matters, because electrical energy is a bottleneck resource. Renewables may be cheap, but they aren't free and we have a lot of other things we need that energy for. If you can make a car go 4 miles with 1kwh of electrical input, that's much better than a car that can got 2 or 3 miles with the same input. Multiply that by the ~1.5 billion cars/trucks in the world presently and that's a huge difference.

Burning liquid fuel in a heat engine typically wastes about 2/3 of the chemical energy as heat. Hybrids do better, but there's only so much you can do.

I don't know what the state of the art for synthesizing liquid fuel is, but I assume there's some significant energy loss there too.

On the other hand, modern permanent-magnet electric motors can be around 95% efficient. Lithium ion batteries typically have coulombic efficiency better than 99%. Actual energy efficiency is a little less due to internal resistance (it takes a higher voltage to charge the battery than you get out when you drain it, so even if amp-hours in is almost equal to amp-hours out, watt hours might be a little different). Charging circuitry also tends to be pretty efficient. Battery-electric drive trains are already so close to optimal efficiency that there's very little that they can actually be improved on, and nothing else comes close.

The tire dust microplastics thing is a real problem, but it's not that much worse for EVs than other cars. Brake dust is much less of an issue on BEVs and hybrids, due to regenerative braking.

Personally I hope the idea of BEVs that haul around 800 pound batteries goes out of fashion (and it might if we could be bothered to electrify our major highways to make huge batteries largely unnecessary), and I also hope cars in general start to get smaller and less numerous. But I think cars are basically here to stay in some form, so they might as well be electric.

gambiting

a month ago

I have a PHEV and I genuienly believe this is the best combination of both, it's so practical with upsides of both drivetrains, but also let's not kid ourselves - PHEVs are vastly more complicated than either just plain ICE or EV cars, you have a lot more stuff that can go wrong. I deal with it by just buying extended warranty for as long as they let me lol, but it's definitely a concern with them.

Lwerewolf

a month ago

The Prius and other HSD cars (i.e anything with a power-split device of the Toyota variety - input-split PSD) are some of, if not flat out the most reliable and simple ICE cars. Permanent atkinson-cycle engine, no turbos because there's no exhaust gas pressure to drive them in the first place (and if there was, it'd be an inefficiency to be rooted out), bulletproof starter/generator especially since the ls600h (double-sided cooling of IGBTs >> no usual IGBT packaging degradation-related failure modes - this was NOT the setup on the 3rd gen prius), still a very efficient power transfer from the engine to the wheels (a big percent is still transferred mechanically), etc, etc.

Adding a bigger battery to those isn't a whole lot of increased complexity. The only issue is making a PHEV that has the same performance characteristics in both EV and hybrid mode - not that it hasn't been done. Specifically on HSD cars, the two electric motors combined, or even just MG2 (the "motor") have way more power than you'd assume - they actually function as an AC-AC converter, converting a significant portion of the engine's output power from mechanical to electric and back to mechanical again. It's essentially the way the eCVT works. Therefore, with a battery (and buck-boost converter) that can support such a load, they can propel the car alone way more than adequately - with a speed limit to protect the "generator" from too high RPM, due to the way the HSD works.

Anyways, it absolutely can be done and it absolutely can be way simpler. If it's a case of a typical modern ICE with a big battery and a motor thrown in somewhere that makes it "hybrid"-ish - i.e. all the ICE complexity + the EV "complexity" (minus the classic starter/alternator) - yeah, no thanks.

IMO: Good examples - the Chrysler Pacifica PHEV. Bad examples - C63 AMG (the PHEV version).

robocat

a month ago

> bulletproof starter

I was told this is not true for 2006 Alphard hybrid (I have one). ~USD1000 part (usually old Toyotas have cheaper parts).

And beware that older hybrids use small (e.g. 50Wh) NiMH batteries - I think they started to change to Lithium in 2017 or something

wiredfool

a month ago

I think a PHEV would be ideal for me -- Bimodal use, mostly a few km trips, and then a few 1000km trips/yr. The long trips are the ones where we wind up filling the car, so space inside/towing is important. (We've got a 7 seater, used to be a renault grand scenic, now a ford galaxy).

OTOH, one of the last times I rented a car, they 'upgraded' me to a PHEV, and I wasn't impressed. It was a tight fit with the kids + luggage, and we didn't even have the dog along. Fuel economy was well worse than plain old diesel, because it turns out when they give you a PHEV with 0km in the battery, it's not much of a hybrid. (This was a Volvo S60).

gambiting

a month ago

Ours is an XC60 T8 and yeah, I do 90% of my day to day driving in EV mode, then few very long distance trips on fuel. But yeah, not much use if it's not charged.

rootusrootus

a month ago

What would you say the bad part is for a BEV?

Personally I hope to never drive another gas-powered vehicle, hybrid or not. I'm very much addicted to the convenience and performance of modern BEVs.

gambiting

a month ago

I drive across Europe few times a year and covering 800 miles in one day is difficult to do in almost every BEV, maybe with the exception of Teslas. Also I had to deal with chargers in Germany a few times and it's been a pain every time(the classic - charger requires an account, the account only accepts german-registered payment card).

But I'm also perfectly happy to admit that it's fine and doable just requires adjustment of expectations, and even the charging network thing I'm sure has solutions if you plan beforehand.

spockz

a month ago

I got the tip from other BEV users for charging in Germany to go off the highway and find something like a shopping center/mall. There they had always plenty fast chargers and something convenient to do as well. Their built in navigation showed them the way. (This was bmw, not Tesla.)

rootusrootus

a month ago

I hear you. This is a choice everyone has to make for themselves. Not everyone will have the same priorities or circumstances.

My longest yearly trip is ~1200km, but that's like once a year. Several times a year I do a 500km trip. On the long haul the additional refueling stops make the trip about 10% longer, on the shorter trip it has more impact, about 15%. Caveat: this is in the western US and superchargers are invariably right next to the freeway, so they don't add much time to the trip.

What really sold it for me was eliminating the trips to the gas station. That is a level of convenience it will be hard to give up.

I'm in the market right now for a new second vehicle, since I'm eliminating the need for a thirsty HD pickup capable of towing our trailer, and what I'm finding is that the market for EVs is not great in the truck space. Couple choices, both with ups and downs, and a little bigger than what I'd prefer (C'mon, Toyota, make us an electric Tacoma). So I'm faced with having to get another ICE vehicle, and the inability to fuel at home bums me out.

thatfrenchguy

a month ago

I mean, you can use Tesla chargers with any car these days in the EU?

brnt

a month ago

But they are a tiny minority of charging point, the market is quite diverse in Europe. And this whole setting up account, installing apps for each and every company, different in each and every country, is really off putting.

I have no idea why they don't just use the kind of dumb payment terminals every unmanned carbohydrate station uses. Works with any card from any country all the time.

rootusrootus

a month ago

Great video, lots of nice details. Now I wonder what technology our local light rail train is using, because I've noticed the gear switch sound (though it just has a single switch at perhaps 10-15 mph or so). Apparently it's a Siemens S70 (there are several varieties of rolling stock, but this is the one that makes the most distinctive sounds).

fransje26

a month ago

Could someone explain the difference between the PWM mode and the pattern mode?

To me, the example of the PWM wave [1] looks like the VFD mode, but:

- instead of varying between [-V..V], varying between [0..V]

- instead of having a regular variation of pulse pattern to get a regular wave, having an irregular pattern.

But that irregular pattern (or non-recurring pattern) only seems to be an illustrative example to match the brown wave shape, and I assume you wouldn't want to have irregular wave patterns to drive your engine?

[1] https://youtu.be/IRJIJPTUXXE?feature=shared&t=406

atahanacar

a month ago

As far as I can understand from the video, pattern is variable frequency PWM.

fransje26

a month ago

So a PWM pattern with a fixed number of pulses that are relatively broadened/shrunk to have a variable wave frequency?

CraigJPerry

a month ago

That video turned out way more interesting than I first thought. I never really considered why the 380 makes that noise, i assumed it was a maintenance issue.

grishka

a month ago

So it's more complicated than I thought it was. Now I'm curious about our Russian trains, especially in subways. They've never made any interesting sounds, it seems. The older (Soviet-era) ones don't make any noticeable sounds at all. The newer ones just make a high-pitched whine that varies in volume (but not frequency I think) when they accelerate or brake.

fotta

a month ago

Anyone know what the BART FOTF trains use? I’m guessing it’s IGBTs but they sound more like fixed PWM switching to pattern mode with pulse drops.

amelius

a month ago

Can't they filter out those sounds with some L's and C's?

rcxdude

a month ago

Not very easily. Firstly, the power involved in these systems is massive, making any inductor or capacitor you put in very expensive (and bulky). Secondly, filtering it out may reduce the sound, but still will have some part of the circuit switching at that frequency, and with the power involved, some part of the inductor will see that and vibrate accordingly. Modern power electronics generally avoids this problem primarily by pushing the switching frequency higher than human hearing (which also has other advantages, like reducing the inductance and capacitance involved). Generally the higher-power the device, the physically bigger it is, and the slower you can switch it without melting it, so bigger systems are stuck at lower frequencies (this is something that's improving as technology develops: so there's the other factor that most train stock is quite old and the designs older still, meaning they switch even slower than your new laptop, even taking everything else into account).

CarVac

a month ago

The motor is a bunch of big Ls, and the Cs are already used to feed the chopper.

amelius

a month ago

A class D amplifier + speaker has a very similar circuit topology, yet here we apply filtering all the time ...

bmicraft

a month ago

Someone might argue that for a speaker the sound is more important than efficiency or even price (per unit of power output)

lockedup

a month ago

Http://www.yahoo.com/news

hejira

a month ago

Fun and educational video!

GavinGruesome

a month ago

Nerd knowledge.

Btw nothing beats the sounds made by both steam- and opposing-piston diesel engines - you can feel the power. Sounds made by electric engines are mostly whining.