@@rogerphelps9939 Yeah, but if they were loud and had those phase switching sounds that sound like gear changing and all the other bells and whistles then they would break the market, surely.
I remember when I first rode on the Jubilee line for the first time when I was younger and when the train pulled in I was actually scared because I thought that there was something wrong with the train and I was like to my mum "why is the train making that noise" to which she replied "I dont know." I was especially convinced the train was faulty because I live on the northern line so I am used to the much quieter motors, and the fact the two lines using an identical design made me even more suspcicious.
@@riorange2083 fascinating to hear how when you were younger you could see this stuff, that I guess adults may have taken for granted. I love that your mum was honest and said she didn't know, I wish everyone could be like that.
There are videos which explain this to a better detail, I love the one by a Japanese railfan who has a working model of AC traction and you can both hear the sound and see the current...
Thank you so much for these, I really appreciate it and I'm looking forward to watching them. I'm sure many other people in the community will value them as well.
@@LKBRICKS1993 thank you so much, really nice to say and that means a lot. From what I understand the new trains will probably make the more humming noise like the Overground trains do.
@@IVA4651 I'm really glad you get it, not everybody can I used to think that as well, so it was a fascinating video for me as well. There's also some great information by some people in the comments, which really adds to this video.
In Melbourne, the Z3 class trams run on 600-750V DC and use a thyristor, called a chopper. I may not be accurate but I understand the instead of changing the voltage to speed up or slow the tram, a square wave is used and the width of the waves is what makes it go fast or slow, the advantage is that full voltage is used but the wave form has more or less square waves in it. I understand this method is used in wheelchairs and golf buggies and so on. The Z3 has a distinctive hum. I don’t hear it on the more modern articulated trams so I don’t know what they do, they still run on DC. I read they use an inverter and perhaps the traction motors are AC, I’ll try and research it. I know the inverters fail and the tram has to be towed in by the R10 truck. There might be a battery somewhere but not quite like the trams at Newcastle (NSW) which don’t have an overhead wire but charge supercaps at each stop.
Yes, absolutely. It's called pulse width modulation ( PWM ). Thyristors can only be "on" ( very low electrical resistance) or "off " ( very high ( virtually infinite) resistance.
I used to go on the Jubilee Line from Westminster to Bermondsey on one of my regular day trips to London from Portsmouth. Never stayed in Central London in the touristy pzrts alsays we t of the beaten track like Bermondsey.
I used to go to places like Ealing Vauxhall hunting down Greasey Spoon Cafes. I only found one in Central London by the Bus/train station called Victoria Cafe. Best Bacon Butties. It has long gone now due to all the new modernisations. I also got the Woolwich Ferry to Thamesmead and went to Crystal Palace. So I saw the real London.
While other part of the world is retiring GTO and even IGBT inverters for more efficient SiC ones, in the UK we are still considering the early VVVFs are modern and efficient... Side note: quite a lot of trains overseas have the inverter renewed during mid-life modernization , why haven't we considered this at all?
The comment isn’t entirely valid. The BREL/ABB built Class 465s had their original Brush GTOs replaced with Hitachi IGBTs. A number of the Northern Class 323s have been upgraded to IGBT. It’s only the remaining electric multiple units with GEC (now Alstom) traction that have not been upgraded.
2:46 ok this isn't correct. DC to AC conversion isn't the difficult part, it's the frequency matching which is the challenge. 3:16 it isn't a device. It's a transistor. They are used WITHIN a VF Drive which is more the miraculous device. 4:48 right you have the wrong end of the stick here. The trains were rushed because the older stock had single leaf doors. Several factors including lower costs, more availability, and faster production meant that the now older GTO based thyristors were used. You have to remember that the 1995 stock use IGBT whereas the 1996 stock use GTO. The 1996 stock was actually one of the last to use GTO. 5:43 what does this even mean??? A normal thyristor??? Thyristors cannot slow down a train. They are either on or off. They cannot be in a state in between. This is why they use PWM to generate an artificial AC frequency. 6:45 IGBT thyristors are just as quiet as GTO thyristors (silent). It’s the motor which produces the sound, not the transistors. Im sorry to point so much out but this may cause confusion to some people, and in some cases its just blatantly wrong. I see so many videos that are incorrect that you hear a completely different explanation between videos.
@@jakewynn thank you so much for the information. You certainly know your stuff. Some bits are different to what I've been told by other people who know a lot as well. The bits I mentioned have more than one source, so I did research this carefully. Doesn't mean it's wrong, I'm just not in a position to comment and I think it's great you're putting stuff here. I hope other people get involved with the discussion as well. For example from what I was told, before the GTO, other equipment was needed for the stepping down and slowing down to reduce the power. You may be right and I might be wrong, but I did use proper sources. However I really appreciate your input here and I hope other people will get involved with saying their point of view as well. I'm learning a lot from you, thank you!
@@LondonUndergroundTubetrains When your thinking about motors the thing to remember is that they are all relatively easy to make spin. A DC motor you can just feed DC voltage, the more voltage, the more torque and it will spin no problem. An AC motor could run off regular mains, but its rotational frequency will be set at 50hz etc. etc. but again it will spin. Its speed control that is the difficult part. How do you control the speed of a motor? This is especially important with AC motors as they generate the most torque when the input frequency is matched to the rotational frequency. (look up a diagram of a synchronous motor on Wikipedia, this may allow it to make more sense) when reading the rest of my comment. Now for DC motors, the way you would do this is with varying the voltage, but DC to DC conversion is difficult. So instead, you use resistors (the formula R = V / I suggests that the more resistance you have, the less voltage that there will be). One way is using resistor banks, start off with one resistor and add resistors in parallel once the train speeds up (remember more resistors in parallel means less overall resistance). This allows for speed control with DC. Now with AC, I previously mentioned that to generate torque, the input frequency needs to match the rotational frequency for the magnetic fields be in the correct place to turn the motor. This is achieved using a Variable Frequency Drive (VF Drive or VFD). What happens is the VF drive uses DC pulses (on, off, on, off) both in the positive and negative direction to create Square wave AC. When this is fed to the motor the current produces an AC sine wave and will drive the AC motor no problem. This uses the transistors within the VF drive to pulse the DC to create the artificial ac wave. Now to the limitations with GTO thyristors. Their switching frequency isn’t as high as IGBT, so after a certain speed they cannot switch fast enough to continue speeding up the train. To overcome this the VF drive creates a pulsing pattern which is no longer pure PWM (where the time off is equal to the time on), I suggest watching this video th-cam.com/video/VOm8ePMg1dE/w-d-xo.html as this dude gets it spot on and can explain it way better than I can. This changing of the pattern is what produces the iconic gear change sound. The 2009 stock despite being IGBT also has a gear change sound, this is because it also switches to pattern-based pulsing but instead at a higher speed to reduce the switching frequency of the transistors. I hope this helps - there’s a lot of misinformation surrounding this because lets face it its complicated so people just start making assumptions and things up. This is something which I have a lot of knowledge about so its painful for me to see misinformation on something which I have spent a lot of time studying :(
@@jakewynn Awesome Jake! Could you tell me why the pattern frequency mode changes so abruptly and produces the gear cange sound instead of changing the frequency in a more progressive way?? And why arent these brusque changes noticed in the aceleration of the train? Thank you
@@ProduccionesJRoman they are preset to change at set speeds to set patterns when the VF drive is programmed. It is simply easier to have less programmed patterns so that the VF drive has to change the DC pulsing as little as possible. The reason why the sound changes so abruptly at the start is that most trains start off in Pure PWM then changes to pattern based pulsing.
Our new equipment sounds exactly like that. Our signal system is AC, but we can't possibly change our motive power from 600 v DC. Actually I think our trains are noisier now with those high pitched electronic 'screams'.
I knew aolid state traction control systems differed but not the real reason. When SWR started the 707s when I couldn't se from the ovebridge, which train was coming in I often mistook them for the 700 Thameslink ones (Both being Siemens Desiro City units) and not the 455 or 300 series ones.
I keep hearing how an AC electric train system is more efficient than the DC systems, but I riding on Brisbane system I heard two clunk sounds every so often, I looked into it and discovered a disadvantage of the AC system, it is that different points of supply every few kilometers can have different phases and you don’t want the wires touching. Therefore magnets in the tracks activate a big mechanical switch that turn off the car’s electricy whilst it enters a dead zone and then another magnet turns the circuit on again. If you don’t want clunks in your journey, ride a trailer carriage. The Melbourne and Sydney systems running on DC don’t have this problem, I wonder how this is done in Europe’s AC systems and is it possible technically to have an AC train system to be in phase? Even if blocks are turned off when there is no train. I saw YT movies on starting a power station and the rigmarole required to manually sync the sine wave. Modern systems seem to do this automatically
Originally, when the trains were DC motored, the method of control was very simple, by switching resistors and motor fields. However what’s fundamentally stopping it is the AC ‘skin effect’, plus it would disrupt the track circuits. And you need DC anyway to supply the onboard auxiliaries.
They probably could've introduced GTO-VVVF on the 1992 stock and IGBT-VVVF on the 1996 stock (they managed to do this on the 1995 stock one year later).
Jubilee Line: This Station is Baker Street change here For the Bakerloo, Circle, Hammersmith and City & Metropolitan Line This Train terminate at Stratford Nexts Stop is Baand Street please stand clear for doors 🚇
The stepping sounds are caused by a multitap transformer. The high current DC supply is passed through a transformer on its way to the motors, as AC motors are generally high voltage, low current. To provide the ranges of power required for different speeds, the AC supply generated by the GTO is passed through different numbers of turns in a transformer, giving steps of output voltage. At each transition, the frequency of the AC switching needs to change back from a high frequency to a low one, before gently increasing again as the train speeds up. The reason the sounds happen as the train is slowing is that the motors are run as generators, and the power is passed back through the transformer and converted back into DC to go back into the power rail. This is called regenerative braking. It saves lots of power that would otherwise be lost as heat. Brake wear is also reduced.
A gate turn-off thyristor is a form of invertor, to turn DC into AC. To do the reverse you use a rectifier (diode bridge). A transformer will only function with AC to change the voltage, but not the frequency.
No, it's the Pulsing pattern with the thyristors changing to prevent from being overloaded. Nothing to do with transformers and tap-changers because that was with older DC motor trains I have a video on the subject.
Absolutely no way that a multi-tap transformer is used. And passing DC (certainly would be high current as it's essentially a short circuit) through a transformer wouldn't do anything.
Strange how you chose a location that muted the more screechy aspects of ac motors.. but then chose a location that deadened the lovely harmonious rising crescendo of dc motors.... editors bias in full bloom?
@ooliver funny, I actually repeated myself a couple of times and realised I my mistake later on. I didn't think about the ads but I suppose I should have done it for that reason, very good point!!!!
I really liked this deep dive on this one particular train class, though the volume difference between your narration and the plain clips was a bit extreme! I also highly rate Z&F Railways' video going through all the different types of technology, with excellent diagrams. But anyone watching this has probably already seen that one :)
Thank you so much for saying about the volume issue, I really appreciate your feedback and I will try and watch that for the next video I do. Please do say if you notice anything else? Would you be okay to please send a link to that Z&F video as I don't think I've seen it?
@@LondonUndergroundTubetrains no problem. I really liked your practical demonstration with the battery :) TH-cam sometimes blocks links even to TH-cam but I’ll give it a go: th-cam.com/video/IRJIJPTUXXE/w-d-xo.html However I am going to save this comment elsewhere in case it doesn’t post. At any rate, “Z&F Railways sound” did get it for me (but of course I already saw it so it might prioritise that).
If electric cars sounded like this then everyone would buy them 💀
That's a great point
Some of them do. My Nissan Leaf hums at low speeds.
@@rogerphelps9939 Yeah, but if they were loud and had those phase switching sounds that sound like gear changing and all the other bells and whistles then they would break the market, surely.
@@rogerphelps9939because it doesn't know the words? 😂😂😂
@@alanclarke4646 Hey! Don't be mean to the poor Nissan 😆
You’ve got to love the sound of the jubilee line
@@GoingUnderground23 I love that you can appreciate it!
I remember when I first rode on the Jubilee line for the first time when I was younger and when the train pulled in I was actually scared because I thought that there was something wrong with the train and I was like to my mum "why is the train making that noise" to which she replied "I dont know." I was especially convinced the train was faulty because I live on the northern line so I am used to the much quieter motors, and the fact the two lines using an identical design made me even more suspcicious.
@@riorange2083 fascinating to hear how when you were younger you could see this stuff, that I guess adults may have taken for granted.
I love that your mum was honest and said she didn't know, I wish everyone could be like that.
I really love hearing that sound on the jubilee line.
I love that you can appreciate it!
Great vid! I found this really interesting and actually learnt something. Thanks!
@@wertrocks123 that means a huge amount, thank you so much for saying.
Also if you have any thoughts on how I can improve the videos, please do say.
Thanks for making this video , I needed to learn all these facts from you , Thank you s-o much and have a happy early christmas
@@michelleturl8213 thank you so much for saying, it's really nice of you and means a lot.
I hope you have a happy Christmas too!
this has and always will be my favourite line on the underground
As an electrical engineer i never knew this, thanks for a fascinating video, gonna look out for this next time I'm in london
@@robertaries2974 That's really kind of you to say and I hope you get to come to London soon.
There are videos which explain this to a better detail, I love the one by a Japanese railfan who has a working model of AC traction and you can both hear the sound and see the current...
- th-cam.com/video/u6AUVwlhCis/w-d-xo.htmlsi=CLnLfcF-j3HmY_hC
- th-cam.com/video/SKu6loq9kfg/w-d-xo.htmlsi=Ag1NzcIWF9oNBc7d
A specific video for Jubilee line trains: th-cam.com/video/7mkuQPw6KCg/w-d-xo.html
Thank you so much for these, I really appreciate it and I'm looking forward to watching them.
I'm sure many other people in the community will value them as well.
A beautiful sound. I noticed it in Dubai metro as well
That's so cool, I didn't know it has that sound there.
Toronto’s T1 trains have a similar sound. Very distinctive.
Beno has done a very detailed video further explaining the intricate of train motors and the sounds
@@AppleOranges12 That's fascinating, would you be able to please put a link to it?
@@LondonUndergroundTubetrains th-cam.com/video/VOm8ePMg1dE/w-d-xo.html
Great video very interesting i love that sound. i wonder if the new trains will make the same sound.
@@LKBRICKS1993 thank you so much, really nice to say and that means a lot.
From what I understand the new trains will probably make the more humming noise like the Overground trains do.
Who knew that such amazing sounds actually have a rather interesting story behind them. I thought the jubilee line had DC motors
@@IVA4651 I'm really glad you get it, not everybody can
I used to think that as well, so it was a fascinating video for me as well.
There's also some great information by some people in the comments, which really adds to this video.
Love the sound :) live near jubilee line used it a lot
Nice, which part of it are you near?
In Melbourne, the Z3 class trams run on 600-750V DC and use a thyristor, called a chopper. I may not be accurate but I understand the instead of changing the voltage to speed up or slow the tram, a square wave is used and the width of the waves is what makes it go fast or slow, the advantage is that full voltage is used but the wave form has more or less square waves in it. I understand this method is used in wheelchairs and golf buggies and so on.
The Z3 has a distinctive hum.
I don’t hear it on the more modern articulated trams so I don’t know what they do, they still run on DC. I read they use an inverter and perhaps the traction motors are AC, I’ll try and research it. I know the inverters fail and the tram has to be towed in by the R10 truck. There might be a battery somewhere but not quite like the trams at Newcastle (NSW) which don’t have an overhead wire but charge supercaps at each stop.
@@darylcheshire1618 that is very interesting and you've explained it really well thank you.
I wonder why the inverters sometimes fail?
Yes, absolutely. It's called pulse width modulation ( PWM ). Thyristors can only be "on" ( very low electrical resistance) or "off " ( very high ( virtually infinite) resistance.
@alanclarke4646 That's a really good explanation, thank you!
I used to go on the Jubilee Line from Westminster to Bermondsey on one of my regular day trips to London from Portsmouth. Never stayed in Central London in the touristy pzrts alsays we t of the beaten track like Bermondsey.
@@TonyWeaving Nice that you could tell which with a touristy bits and which were not.
I used to go to places like Ealing Vauxhall hunting down Greasey Spoon Cafes. I only found one in Central London by the Bus/train station called Victoria Cafe. Best Bacon Butties. It has long gone now due to all the new modernisations. I also got the Woolwich Ferry to Thamesmead and went to Crystal Palace. So I saw the real London.
in germany berlin the "S-Bahn" also sings but there its more of a choir sound but perfect sync
@@shadowplayerbro4900 That's so cool, I hope to hear it one day!
As a visitor ilove that sounds and always thought it was on allubetrains.
@@xr6lad really nice of you to say and most people think the same, I only recently found out myself.
Of course, class 323 electric units make a noise very much like this as well.
@@stephenduncan3605 That's a very good point, thank you for adding that in!
Memories of the 465/6s too
You can find this sound in many countries. I heard it first on the Berlin S-Bahn.
@@norbertk5400 That's very cool, I didn't know that thank you.
While other part of the world is retiring GTO and even IGBT inverters for more efficient SiC ones, in the UK we are still considering the early VVVFs are modern and efficient... Side note: quite a lot of trains overseas have the inverter renewed during mid-life modernization , why haven't we considered this at all?
@@barrielui That's a very clever and good point!
I think you have very cleverly nailed it!
mostly Japan
@itechcircle9410 fascinating!
The comment isn’t entirely valid. The BREL/ABB built Class 465s had their original Brush GTOs replaced with Hitachi IGBTs. A number of the Northern Class 323s have been upgraded to IGBT. It’s only the remaining electric multiple units with GEC (now Alstom) traction that have not been upgraded.
@bfapple That's fascinating, thank you so much, I really appreciate your help.
Memories of the 465/6s
I like that
Awesome video my new friend!!
@@250renfe thank you so much friend, it's really nice of you to say
Well look what the algo has graced me with today
@@rich-tp2dx you are very kind, thank you
2:46 ok this isn't correct. DC to AC conversion isn't the difficult part, it's the frequency matching which is the challenge.
3:16 it isn't a device. It's a transistor. They are used WITHIN a VF Drive which is more the miraculous device.
4:48 right you have the wrong end of the stick here. The trains were rushed because the older stock had single leaf doors. Several factors including lower costs, more availability, and faster production meant that the now older GTO based thyristors were used. You have to remember that the 1995 stock use IGBT whereas the 1996 stock use GTO. The 1996 stock was actually one of the last to use GTO.
5:43 what does this even mean??? A normal thyristor??? Thyristors cannot slow down a train. They are either on or off. They cannot be in a state in between. This is why they use PWM to generate an artificial AC frequency.
6:45 IGBT thyristors are just as quiet as GTO thyristors (silent). It’s the motor which produces the sound, not the transistors.
Im sorry to point so much out but this may cause confusion to some people, and in some cases its just blatantly wrong. I see so many videos that are incorrect that you hear a completely different explanation between videos.
@@jakewynn thank you so much for the information.
You certainly know your stuff.
Some bits are different to what I've been told by other people who know a lot as well. The bits I mentioned have more than one source, so I did research this carefully.
Doesn't mean it's wrong, I'm just not in a position to comment and I think it's great you're putting stuff here. I hope other people get involved with the discussion as well.
For example from what I was told, before the GTO, other equipment was needed for the stepping down and slowing down to reduce the power.
You may be right and I might be wrong, but I did use proper sources.
However I really appreciate your input here and I hope other people will get involved with saying their point of view as well.
I'm learning a lot from you, thank you!
@@LondonUndergroundTubetrains When your thinking about motors the thing to remember is that they are all relatively easy to make spin.
A DC motor you can just feed DC voltage, the more voltage, the more torque and it will spin no problem.
An AC motor could run off regular mains, but its rotational frequency will be set at 50hz etc. etc. but again it will spin.
Its speed control that is the difficult part.
How do you control the speed of a motor? This is especially important with AC motors as they generate the most torque when the input frequency is matched to the rotational frequency. (look up a diagram of a synchronous motor on Wikipedia, this may allow it to make more sense) when reading the rest of my comment.
Now for DC motors, the way you would do this is with varying the voltage, but DC to DC conversion is difficult. So instead, you use resistors (the formula R = V / I suggests that the more resistance you have, the less voltage that there will be). One way is using resistor banks, start off with one resistor and add resistors in parallel once the train speeds up (remember more resistors in parallel means less overall resistance). This allows for speed control with DC.
Now with AC, I previously mentioned that to generate torque, the input frequency needs to match the rotational frequency for the magnetic fields be in the correct place to turn the motor. This is achieved using a Variable Frequency Drive (VF Drive or VFD). What happens is the VF drive uses DC pulses (on, off, on, off) both in the positive and negative direction to create Square wave AC. When this is fed to the motor the current produces an AC sine wave and will drive the AC motor no problem. This uses the transistors within the VF drive to pulse the DC to create the artificial ac wave.
Now to the limitations with GTO thyristors. Their switching frequency isn’t as high as IGBT, so after a certain speed they cannot switch fast enough to continue speeding up the train. To overcome this the VF drive creates a pulsing pattern which is no longer pure PWM (where the time off is equal to the time on), I suggest watching this video th-cam.com/video/VOm8ePMg1dE/w-d-xo.html as this dude gets it spot on and can explain it way better than I can. This changing of the pattern is what produces the iconic gear change sound. The 2009 stock despite being IGBT also has a gear change sound, this is because it also switches to pattern-based pulsing but instead at a higher speed to reduce the switching frequency of the transistors.
I hope this helps - there’s a lot of misinformation surrounding this because lets face it its complicated so people just start making assumptions and things up. This is something which I have a lot of knowledge about so its painful for me to see misinformation on something which I have spent a lot of time studying :(
@@jakewynn this is absolutely brilliant information, you've taken it to a whole new level, thank you so much!
@@jakewynn Awesome Jake! Could you tell me why the pattern frequency mode changes so abruptly and produces the gear cange sound instead of changing the frequency in a more progressive way?? And why arent these brusque changes noticed in the aceleration of the train? Thank you
@@ProduccionesJRoman they are preset to change at set speeds to set patterns when the VF drive is programmed. It is simply easier to have less programmed patterns so that the VF drive has to change the DC pulsing as little as possible. The reason why the sound changes so abruptly at the start is that most trains start off in Pure PWM then changes to pattern based pulsing.
I like this sound 😅
@arcamaya95 I love that you can see how great it is!
Fascinating......
Some, not all, of the Class 465s on SouthEastern make the same sound, because they use the same technology.
The Met-Camm built units with GEC (now Alstom) traction. They are slowly, slowly being withdrawn.
Very good point!
great vid! subbed
@theringsmc thank you so much, that's really kind of you and means a lot!
Our new equipment sounds exactly like that. Our signal system is AC, but we can't possibly change our motive power from 600 v DC. Actually I think our trains are noisier now with those high pitched electronic 'screams'.
@@JoseNunez-hh1yr fascinating, do you think it's getting louder as the equipment gets older, or something else?
It sounds like a Gearbox
Very good point, I suppose in some ways it is.
I knew aolid state traction control systems differed but not the real reason. When SWR started the 707s when I couldn't se from the ovebridge, which train was coming in I often mistook them for the 700 Thameslink ones (Both being Siemens Desiro City units) and not the 455 or 300 series ones.
That is really interesting and lovely to hear about those trains, thank you!
I keep hearing how an AC electric train system is more efficient than the DC systems, but I riding on Brisbane system I heard two clunk sounds every so often, I looked into it and discovered a disadvantage of the AC system, it is that different points of supply every few kilometers can have different phases and you don’t want the wires touching. Therefore magnets in the tracks activate a big mechanical switch that turn off the car’s electricy whilst it enters a dead zone and then another magnet turns the circuit on again. If you don’t want clunks in your journey, ride a trailer carriage.
The Melbourne and Sydney systems running on DC don’t have this problem, I wonder how this is done in Europe’s AC systems and is it possible technically to have an AC train system to be in phase? Even if blocks are turned off when there is no train.
I saw YT movies on starting a power station and the rigmarole required to manually sync the sine wave. Modern systems seem to do this automatically
@@darylcheshire1618 That's fascinating in a whole load of information I had no idea about, thank you.
Ha no 😂
i prefer 92 or 09 stock sounds, much of a violence symphony to me
I can understand that, I like that you can discern all the sounds.
Now here’s a crazy question for the train geeks and electrical engineers, why not just put alternating current down the rails
In the first place?
Originally, when the trains were DC motored, the method of control was very simple, by switching resistors and motor fields. However what’s fundamentally stopping it is the AC ‘skin effect’, plus it would disrupt the track circuits. And you need DC anyway to supply the onboard auxiliaries.
Great question!
Very impressive answer!
The sound of modern London .
@@paullucas7998 Good point, like it!
They probably could've introduced GTO-VVVF on the 1992 stock and IGBT-VVVF on the 1996 stock (they managed to do this on the 1995 stock one year later).
@@itechcircle9410 That's a very useful detail, thank!
Could have, yes, but the commercial contracts at the time didn’t allow for it.
@bfapple That's fascinating, I'd love to please know more about that if you have any more information?
A more technical description and demonstration of why the motors make a noise, th-cam.com/video/mKpIqNNc9Kw/w-d-xo.htmlsi=PpV7ITsDSk3VQ0qF
Jubilee Line: This Station is Baker Street change here For the Bakerloo, Circle, Hammersmith and City & Metropolitan Line This Train terminate at Stratford Nexts Stop is Baand Street please stand clear for doors 🚇
Sound like Melbourne train. 0:37
@@Maxparson299 very cool, I'd love to hear that in person sometime.
The stepping sounds are caused by a multitap transformer. The high current DC supply is passed through a transformer on its way to the motors, as AC motors are generally high voltage, low current.
To provide the ranges of power required for different speeds, the AC supply generated by the GTO is passed through different numbers of turns in a transformer, giving steps of output voltage. At each transition, the frequency of the AC switching needs to change back from a high frequency to a low one, before gently increasing again as the train speeds up.
The reason the sounds happen as the train is slowing is that the motors are run as generators, and the power is passed back through the transformer and converted back into DC to go back into the power rail. This is called regenerative braking. It saves lots of power that would otherwise be lost as heat. Brake wear is also reduced.
Thank you for writing and explaining it so well, I hope lots of people read your comment!
Are you sure there's transformer involved?
A gate turn-off thyristor is a form of invertor, to turn DC into AC. To do the reverse you use a rectifier (diode bridge). A transformer will only function with AC to change the voltage, but not the frequency.
No, it's the Pulsing pattern with the thyristors changing to prevent from being overloaded. Nothing to do with transformers and tap-changers because that was with older DC motor trains I have a video on the subject.
Absolutely no way that a multi-tap transformer is used. And passing DC (certainly would be high current as it's essentially a short circuit) through a transformer wouldn't do anything.
Some people call it Chopping? I don't get that?
I think it's because the different steps in the sound are not smooth or soft, they're like a hard change in pitch.
@@LondonUndergroundTubetrains ah I see
Strange how you chose a location that muted the more screechy aspects of ac motors.. but then chose a location that deadened the lovely harmonious rising crescendo of dc motors.... editors bias in full bloom?
really dragged it out to 8 minutes for those ads right?
@ooliver funny, I actually repeated myself a couple of times and realised I my mistake later on.
I didn't think about the ads but I suppose I should have done it for that reason, very good point!!!!
B A S S
1:28 this is not the motor making this sound 😂 unfair comparison lol
@@jakewynn please see my reply to your other comment, I really appreciate your input.
It's just a noise
Fair enough, I totally respect it's not your thing.
I really liked this deep dive on this one particular train class, though the volume difference between your narration and the plain clips was a bit extreme!
I also highly rate Z&F Railways' video going through all the different types of technology, with excellent diagrams. But anyone watching this has probably already seen that one :)
Thank you so much for saying about the volume issue, I really appreciate your feedback and I will try and watch that for the next video I do.
Please do say if you notice anything else?
Would you be okay to please send a link to that Z&F video as I don't think I've seen it?
@@LondonUndergroundTubetrains no problem. I really liked your practical demonstration with the battery :)
TH-cam sometimes blocks links even to TH-cam but I’ll give it a go: th-cam.com/video/IRJIJPTUXXE/w-d-xo.html
However I am going to save this comment elsewhere in case it doesn’t post. At any rate, “Z&F Railways sound” did get it for me (but of course I already saw it so it might prioritise that).