AC whining and Desiro alarm sound!

[RichW1]

Hi all,

I understand AC motors are the reason for the annoying whining sound made on rolling stock like Pendolino's and even Great Eastern stock etc? Does anyone with engineering expertise or otherwise know if this has to sound so prominent? We didn't used to have AC motors so why the change? I preferred it as it was!

Secondly, on the Desiro's and other modern stock like the Great Eastern, there is a REALLY annoying and loud repeating alarm sound you all know when they pull out of a platform or come in, and I am just wondering....why the hell is it there? What is that noise? Why is this considered ok? Is quieter stock like in other parts of the world so hard to purchase or build? Do we have to put up with this sound forever?! I have not heard it anywhere on a train in Europe (yet) so why do we have to be the only ones. Other than that the stock is amazing.

 

[455driver]

I understand AC motors are the reason for the annoying whining sound made on rolling stock like Pendolino's and even Great Eastern stock etc? Does anyone with engineering expertise or otherwise know if this has to sound so prominent? We didn't used to have AC motors so why the change? I preferred it as it was!

AC motors are more powerful for their size, need less routine maintenance and last much longer than DC motors.

Secondly, on the Desiro's and other modern stock like the Great Eastern, there is a REALLY annoying and loud repeating alarm sound you all know when they pull out of a platform or come in, and I am just wondering....why the hell is it there? What is that noise? Why is this considered ok?

Never heard that, is it from the cab or in every coach?

Is quieter stock like in other parts of the world so hard to purchase or build? Do we have to put up with this sound forever?! I have not heard it anywhere on a train in Europe (yet) so why do we have to be the only ones. Other than that the stock is amazing.

Euro stock tends to be built up to a standard, ours tends to be built down to the cheapest possible price oops I mean built in a "value for money" way!

 

[RichW1]

The sound in the EMU rolling stock is very loud and everyone can hear it. You'll know the sound so maybe I'm describing it badly. Youtube any West Coast Main Line clip and when you see a 350 come in or out of a station, it's the obvious sound it makes. It really is unique to all new emu stock it seems and diesels were ironically quieter in some cases!

 

[Monty]

That 'alarm' type sound is because of the trains AC traction motors, most AC motored units make a similar sound when stopping at stations and when pulling away. But like the Class 323s, the noise a Desiro makes is quite distinctive.

 

[455driver]

Ah the sound from the motor coaches, yes it is quite distinctive, its the induction (traction) motors and is to do with the way the motors are controlled.

Our 444 and 450s have had the software changed a couple of times which has changed the noise quite a bit, in fact I rang a set in as faulty because it was making a "strange" noise when it was just the "new" noise and was told that the noise was normal.

 

[thetangoman]

Secondly, on the Desiro's and other modern stock like the Great Eastern, there is a REALLY annoying and loud repeating alarm sound you all know when they pull out of a platform or come in, and I am just wondering....why the hell is it there? What is that noise? Why is this considered ok? Is quieter stock like in other parts of the world so hard to purchase or build? Do we have to put up with this sound forever?! I have not heard it anywhere on a train in Europe (yet) so why do we have to be the only ones. Other than that the stock is amazing.

Class 380's have this, It is an external sound, not exactly sure what it is for though:roll:

 

[RichW1]

Well thanks for the info. AC traction motors of all things?! I knew AC traction motors whined but to make that alarm sound which is just very annoying and loud seems not very 'modern' to me! AC motors appear to be quite my personal culprit in many ways within modern stock or retro-fitted stock. What a shame. Wonder how they do it n the continent then?!

 

[notadriver]

The sound could be Insulated Gate Bipolar Transistors (IGBT) for the traction motors doing their work. As mentioned AC motors can be smaller and more powerful than DC motors and require far less maintenance but most importantly can regenerate electricity back into the supply while braking the train.

 

[bronzeonion]

I agree the Desiro UFO noise is horrible.

 

[HSTEd]

In theory you could regenerate from DC motors, but if you are not using a low voltage DC supply it becomes.... problematic.

 

[thetangoman]

I agree the Desiro UFO noise is horrible.

Agreed, could it be an electronic warning noise as it sounds too artificial to come from the ac motors imo

 

[Muzer]

I like the noise. Maybe I'm weird. Then again, I do rather like the distinctive noises certain units make. 323s (and the LU stock that makes similar noises, Jubilee IIRC) are easily my favourite

 

[O L Leigh]

Warning noise...? Warning of what?

It is, as has already been said, the traction equipment doing what it does, either under power or for regenerative braking. It is simply a feature of the system and has been around since the Networkers. Each class has slightly different equipment and so it makes a slightly different noise. However, it is all doing the same thing.

O L Leigh

 

[bronzeonion]

Agreed, could it be an electronic warning noise as it sounds too artificial to come from the ac motors imo

No definitely just one of the sounds the traction systems make!

I like the sound of the Electrostars or any other AC motored stock but the Desiro is one I dislike.

 

[edwin_m]

DC motors make a kind of humming noise, probably a mixture of "mains hum" and a component associated with the commutation and therefore rising with speed. If driven by traditional camshaft you also hear the periodic clicking as it rotates, and more modern chopper controllers will have their own sound which is probably a fixed frequency.

AC motors need current at a frequency that depends on speed, which is generated from DC by a traction converter. The pitch of the traction converters will rise with speed until it gets near the limit of the electronics or a frequency that might interfere with signalling, when it starts using a different method to generate the AC waveform and "changes gear" down to a lower tone before rising again. The reverse happens with regenerative or rheostatic braking.

This was particularly noticaable with the first generation AC traction packages on 323s and Networkers, which use GTO thyristors that can only work at lower frequencies close to those that some signalling systems also use (Reeds). Though I'm not a frequent user of these EMUs, to me the newer ones are better as the IGBT equipment runs at well above the signalling frequencies and doesn't have to chop and change so much.

Most Continental railways use signalling with much better immunity than the older types still used on some electric routes in the UK. This may mean that even the older GTO drives overseas can work with fewer sudden changes of tone.

 

[upnorth71]

Indeed that flying saucer sound is not the most pleasing feature. I thought these sounds were not the tractions motors (indeed modern AC motors tend to be quieter than DC motors) but rather the inverters. However, inverters can be "tuned" to emit less disturbing sounds. Siemens inverters tend to have "distinctive" sounds, perhaps these were not tuned as such to save on costs.

 

[edwin_m]

The sound depends on the frequency which is produced by the converters and fed into the motors, so both will be making sound at the same pitch. The frequency depends on the speed of the motor so you can't have an AC drive that runs the converters at a fixed frequency.

 

[455driver]

I find it more worrying when I am braking and the noise stops as it means the wheels have picked up and the train is "doing a Torville and Dean".

 

[317666]

At least with the Desiros from my experience, it's very hard to hear the motors from inside the saloon as they're very well insulated and quiet. So you only really have to put up with it for the 30 seconds or so it takes for the train to arrive at your station.

 

[starrymarkb]

Indeed - For Other interesting AC motor sounds see the Siemens Taurus. For obnoxious ones see the Berlin S-Bahn 481s and DB's 101 and 146 Locomotives...

 

[Alfie1014]

This is one of the best Taurus videos around http://www.youtube.com/watch?v=aRf30pVGMp4 but I can't work out whether it is 'real' or digitally manipulated. Enjoy.

 

[Aictos]

That 'alarm' type sound is because of the trains AC traction motors, most AC motored units make a similar sound when stopping at stations and when pulling away. But like the Class 323s, the noise a Desiro makes is quite distinctive.

That's what I was going to say

 

[317666]

Indeed - For Other interesting AC motor sounds see the Siemens Taurus. For obnoxious ones see the Berlin S-Bahn 481s and DB's 101 and 146 Locomotives...

Personally I quite like the sounds of the 481s, 101s and (older) 146s, but then again I don't have to put up with them day in day out! One strange sounding one is the S-Bahn 423s:
http://www.youtube.com/watch?v=aIqdEWCXt7o

 

[starrymarkb]

With the 101/146 it's the shriek as they pass about 10mph that sets me on edge It's similar to a vehicle with a dodgy fanbelt (that noise has the same effect on me!)

with the 481s its the initial noise before the first 'gear change' - it got rather annoying when we got to the Hbf an hour before our ICE with S-Bahns howling every couple of mins...

I do like the lower tone of the 423

 

[antharro]

Mmm, I don't mind the sound at all. Of stock that have this sound, I travel most frequently on 444s and 450s. As has been pointed out, they have changed over time; I think I preferred how they sounded back in 2006/7 than now, but it's not a nuisance or annoying. And it can only just about be heard inside the train, so no headache from there.

Surprised no one's mentioned the 96ts on the Jubilee line. One of the last examples of GTO thyristors, if I remember correctly?

 

[sutty]

I love the sound the 350's make. I travel on them every day, to and from work. It's hardly a big deal.

The only thing that's ever set me on edge with them is the huge clunk the pan makes going through a (presumably) neutral section. That's remedied by not sitting there

 

[455driver]

Its the vacuum circuit breaker.

 

[causton]

This is one of the best Taurus videos around http://www.youtube.com/watch?v=aRf30pVGMp4 but I can't work out whether it is 'real' or digitally manipulated. Enjoy.

That is amazing! I also found this one http://www.youtube.com/watch?v=VJGs9BbJYyA which sounds the same so it might not be... that sound is seriously amazing though!

 

[sutty]

Its the vacuum circuit breaker.

It scared the bejesus out of me the first time it happened. I just sleep through it now

 

[455driver]

It scared the bejesus out of me the first time it happened. I just sleep through it now

It does "clunk" a bit doesnt it!