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

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

#51

Post by exabrial »

bobthepanda wrote: post #44
exabrial wrote: post #38

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…

25kv 50/60Hz is the norm. The German standard you are thinking of is 15kv 16.7Hz.

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

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

#52

Post by vvanders »

jimmaswell wrote: post #18

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.

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.

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

#53

Post by gorlilla »

asciii wrote: post #30
jkingsman wrote: post #10

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

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

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

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

#54

Post by NikkiA »

theideaofcoffee wrote: post #13

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, curre…

The Mercury Arc rectifiers that powered the earliest electric locomotives were prettier to observe though:

https://www.youtube.com/watch?v=whF80m6oQZ8

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

#55

Post by bmicraft »

asciii wrote: post #30
jkingsman wrote: post #10

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

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

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

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

#56

Post by bmicraft »

amelius wrote: post #20
CarVac wrote: post #17

Earlier quoted context omitted.

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

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

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

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

#57

Post by brnt »

thatfrenchguy wrote: post #36
gambiting wrote: post #32

Earlier quoted context omitted.

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 adju…

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

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.

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

#58

Post by Animats »

rwmj wrote: post #27
theideaofcoffee wrote: post #13

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, curre…

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.

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...

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

#59

Post by rob74 »

asciii wrote: post #30
jkingsman wrote: post #10

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

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

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...

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