Desiro Traction Motor Noise

[MCR247]

Hi all

I’m currently having a debate with a friend about the noises the traction motors on UK Desiros (350s, 360s, 380s, 444s and 450s) make (sometimes referred to as the UFO sound) and hoping you guys have a better memory than I do. I’m ignoring the Desiro Cities for now as they’re much more recent.

As I seem to recall, originally the Desiros made a slightly different noise than they do and have for the last 10 years say. It was quite a similar sound - you wouldn’t confuse it for a networker or anything - but it was a different pitch/frequency. Maybe the timing of the noises changed too. I’m a bit fuzzy on when they changed, but I feel like it was sometime around the 350/2s being delivered. I want to say these /2s. made the ‘new’ noise from delivery but I can’t recall when the other classes changed? (And also why?) My friend has no recollection of any of this and is adamant they’ve always sounded the same.

I’ve had a Quick look on YouTube but I can’t seem to find anything to confirm my memories! I appreciate this is probably quite niche even for RailUk

Thanks in advance!

 

[172007]

When they first move off they sound like the start of the Top Gear them tune.

 

[Sad Sprinter]

Hi all

I’m currently having a debate with a friend about the noises the traction motors on UK Desiros (350s, 360s, 380s, 444s and 450s) make (sometimes referred to as the UFO sound) and hoping you guys have a better memory than I do. I’m ignoring the Desiro Cities for now as they’re much more recent.

As I seem to recall, originally the Desiros made a slightly different noise than they do and have for the last 10 years say. It was quite a similar sound - you wouldn’t confuse it for a networker or anything - but it was a different pitch/frequency. Maybe the timing of the noises changed too. I’m a bit fuzzy on when they changed, but I feel like it was sometime around the 350/2s being delivered. I want to say these /2s. made the ‘new’ noise from delivery but I can’t recall when the other classes changed? (And also why?) My friend has no recollection of any of this and is adamant they’ve always sounded the same.

I’ve had a Quick look on YouTube but I can’t seem to find anything to confirm my memories! I appreciate this is probably quite niche even for RailUk

Thanks in advance!

Yes I know exactly what you mean.

 

[trainmania100]

Used to hear a fading in sort of flashing noise when 450s started to accelerate out of Portsmouth harbour when I visited regularly. It was a unique sound that would gradually become constant as the train sped up.

I filmed this video a long time ago, it may have some sounds you mention;

 

[SWRtrainfan]

It was the fitting of regenerative braking that changed the noise. Prior to this, the transition in noise that currently occurs at 20mph used to happen at 5mph or so. All 444s and 450s had it fitted by March 2012.

Funnily enough I actually asked this question over a year ago too, but I then found out it's due to this months later.

 

[MCR247]

Yes I know exactly what you mean.

Used to hear a fading in sort of flashing noise when 450s started to accelerate out of Portsmouth harbour when I visited regularly. It was a unique sound that would gradually become constant as the train sped up.

I filmed this video a long time ago, it may have some sounds you mention;

Thank you both for confirming I’m not going crazy!

It was the fitting of regenerative braking that changed the noise. Prior to this, the transition in noise that currently occurs at 20mph used to happen at 5mph or so. All 444s and 450s had it fitted by March 2012.

Funnily enough I actually asked this question over a year ago too, but I then found out it's due to this months later.

Ah great thank you for solving this for me!

 

[tfw756rider]

I do remember the 350s (/1s and /2s) making only the higher-pitched version of the "UFO sound" back in the second half of the 2000s and up to around 2012.

In more "recent" times (say 2018-ish), when I started to hear them making the lower-pitched then higher-pitched versions of the "UFO sound" when pulling away, I thought "I don't remember the lower-pitched version of the sound, only the higher-pitched one", and now, reading this thread, I'm like "ah, so it was changed?".

Maybe the change needed to be made at the same time as they got uprated from 100mph to 110mph (which I believe was 2012 for the /1s and 2018 for the /2s)? I do remember reading that Siemens said that a lot of changes needed to be made and perhaps that was one of them?

I'm guessing the /3s and /4s have never made only the higher-pitched version of the "UFO sound" when pulling away (always the lower-pitched then higher-pitched versions of the sound), as they were built as 110mph from new?

 

[MCR247]

I do remember the 350s (/1s and /2s) making only the higher-pitched version of the "UFO sound" back in the second half of the 2000s and up to around 2012.

In more "recent" times (say 2018-ish), when I started to hear them making the lower-pitched then higher-pitched versions of the "UFO sound" when pulling away, I thought "I don't remember the lower-pitched version of the sound, only the higher-pitched one", and now, reading this thread, I'm like "ah, so it was changed?".

Maybe the change needed to be made at the same time as they got uprated from 100mph to 110mph (which I believe was 2012 for the /1s and 2018 for the /2s)? I do remember reading that Siemens said that a lot of changes needed to be made and perhaps that was one of them?

I'm guessing the /3s and /4s have never made only the higher-pitched version of the "UFO sound" when pulling away (always the lower-pitched then higher-pitched versions of the sound), as they were built as 110mph from new?

I’m not sure it was related to 110mph upgrades as 360s and 450s and 444s changed too

 

[Discuss223]

I noticed one of the Desiros with TransPennine Express has had some equipment fitted to the undercarriage, looks to be some sort of heater or cooler, only seen it on one unit, but can't for the life of me remember the number.

 

[antharro]

I often wondered about this. I figured it was a performance related mod. They certainly used to change from the "wobbly UFO" sound to "eeeeeeee" much much sooner than they do now. Back in the day, the lass I was dating would let me know which train she was on by telling me either that it was a "pig" (442) or an "eee" (444).

 

[NSEWonderer]

I do wonder if these performance mods that happened around March 2012 with the late second phase, led to the trains accelerating much faster? I always thought they seemed more nippy when the second phase happened around 5mph than the roughly 20mph transition.
I know Desiros are limited to about 50% of their actual power draw but I wonder what actual change to acceleration did the later second phase have? Put some videos for some basic visualisation, of course weather conditions, driving technique etc will differ.

Pre Regenative Braking Upgrade

Post Regenative Braking Upgrade

 

[Russel]

Strange how you don't notice small things like this have changed until it's pointed out!

 

[NSEWonderer]

Indeed, I myself completely forgot the 350s also had one phase tone which is what is considered the second or high phase till roughly around the same time the older Desiro's started taking traction updates:

350 Old Inverter Phase

350 Current Inverter Phasing

**Credits to the Video Owners**

 

[365 Networker]

Indeed, I myself completely forgot the 350s also had one phase tone which is what is considered the second or high phase till roughly around the same time the older Desiro's started taking traction updates:

350 Old Inverter Phase

350 Current Inverter Phasing

**Credits to the Video Owners**

The original AC pitch was slightly different - go to 1:10

 

[NSEWonderer]

Nice!, it does show that for most of the Original Desiros the preferred inverter style seems to have landed one a "Two Phase" variant with the second phase coming into play around the 15-20mark in general.

What is cant tell is how it affected acceleration especially with the DC units which years ago when I used to frequent Waterloo(before the regen change), the 444 seemed to pick up quicker than I remember now unless that's nostalgic bias.

 

[DJH1971]

I once nicknamed the 350's as 'banshees'.

 

[brad465]

Class 700s from memory sound slightly different on AC OHLE vs DC Third Rail, which I doubt is a coincidence.

 

[swt_passenger]

Class 700s from memory sound slightly different on AC OHLE vs DC Third Rail, which I doubt is a coincidence.

The traction converters, which produce 3 phase AC at varying frequency to drive the motors, use different internal switching frequencies to guard against interference with trackside equipment. Some equipments such as track circuits are slightly different in AC and DC areas.

 

[Ted633]

Class 700s from memory sound slightly different on AC OHLE vs DC Third Rail, which I doubt is a coincidence.

The 'UFO' sound is non-existant when on AC (I think so anyway, don't see them on AC that often)

 

[NSEWonderer]

700s have indeed always had different sounds when on AC vs DC but since introduction there has been no changes to these inverter phases since unlike when the Original Desiros were tweaked around 2012.

 

[MCR247]

The 'UFO' sound is non-existant when on AC (I think so anyway, don't see them on AC that often)

They sound pretty Aventra like on AC

 

[TT-ONR-NRN]

They sound pretty Aventra like on AC

Do you think?
I think they sound more like the 465/0/1 or 395s, though obviously at a different pitch and it’s more of a consistent sound, less whiny.

 

[MCR247]

Do you think?
I think they sound more like the 465/0/1 or 395s, though obviously at a different pitch and it’s more of a consistent sound, less whiny.

I typed aventra but I was actually thinking of mk2 electrostars like 387s, except 700s on AC don’t ‘progress’ like electrostars do, and stay more constant like Hitachi 395s/465s. So yeah I’d say somewhere halfway inbetween

 

[AM9]

The subject has been discussed here before, both regarding the Desiro UK (classes 350, 444 & 450), and Desiro Citys (classes 700, 707 & 717). The general consensus was that the modulated ('martian space ship') tone was generated when the traction system was fed by the bus with a DC voltage, which meant that switching harmonics were spread over a band, therefore reducing its interference to the on-board safety systems and the signalling circuits by the tracks. When the ac/DC Desiro City units were designed, it was found that when running under OLE, the bus voltage had ripple that in itself spread the interference form the inverters over a band such that further modulation of the inverter frequencies was unnecessary. Hence the class 700s and 717s, emitting a single high pitched tone when running on ac, - the ac variation not being easily heard as there is a buzz directly from the transformers anyway.

 

[TT-ONR-NRN]

I typed aventra but I was actually thinking of mk2 electrostars like 387s, except 700s on AC don’t ‘progress’ like electrostars do, and stay more constant like Hitachi 395s/465s. So yeah I’d say somewhere halfway inbetween

I wouldn’t say 395/465s are constant. The whine is very much ascending as they take off, and indeed when 465/0/1s are going over Charing Cross and the acceleration is going up and down you hear them going nuurrRRRRRRRRRuuuuurr.

 

[D365]

I wouldn’t say 395/465s are constant. The whine is very much ascending as they take off, and indeed when 465/0/1s are going over Charing Cross and the acceleration is going up and down you hear them going nuurrRRRRRRRRRuuuuurr.

That reads to me like a description of the underlying motor sounds [as opposed to the inverter electronics].

 

[TT-ONR-NRN]

That reads to me like a description of the underlying motor sounds [as opposed to the inverter electronics].

I’m talking about the high pitched wail that starts up when it leaves.

 

[Silent]

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