Electrostar "Buzzing" Noise

[SpacePhoenix]

In the clip below, what's making the "buzzing" noise that's coming from the coach with the pan when the Electrostar is in AC mode? They only seem to make that noise when in AC mode, I've never seen any clips of them where they make that noise in DC mode so it's got to be something to do with their AC mode?

https://www.youtube.com/watch?v=jI8pPgkuTtU

 

[Domh245]

That'd be transformer, which transforms the 25kV AC voltage from the OLE to something usable by the onboard equipment

 

[richieb1971]

Any reason they go woo woo woo woo as they go past?

 

[slick]

The sound of the 3 phase AC traction motors on the other 3 cars, they have regenerative braking so you'll hear it when braking and accelerating.

 

[SpacePhoenix]

Why are the transformers so noisy on the Electrostars? I can't think of any other class of EMU running on AC that I've seen videos of that have such noisy transformers

 

[AM9]

Why are the transformers so noisy on the Electrostars? I can't think of any other class of EMU running on AC that I've seen videos of that have such noisy transformers

It depends on the mounting and location of standard transformers whether they resonate the bodywork or not. Most of the MKI EMUs had transformers that you could hear the higher power being drawn through.
--- old post above --- --- new post below ---

Any reason they go woo woo woo woo as they go past?

Much of that sound is from the drive pinions on the motors/axles. When new, the gears mesh well with minimum clearance, but as they get more used, the whirring noises can be heard more. When the train is coasting, slight lontitudonal surges owing to track imperfections sometimes cause the gears to make chirping noises as the teeth go from pulling to pushing.

 

[physics34]

It depends on the mounting and location of standard transformers whether they resonate the bodywork or not. Most of the MKI EMUs had transformers that you could hear the higher power being drawn through.
--- old post above --- --- new post below ---


Much of that sound is from the drive pinions on the motors/axles. When new, the gears mesh well with minimum clearance, but as they get more used, the whirring noises can be heard more. When the train is coasting, slight lontitudonal surges owing to track imperfections sometimes cause the gears to make chirping noises as the teeth go from pulling to pushing.

Finally I think I've found someone who can explain to me how a camshaft works!!

 

[DownSouth]

Any reason they go woo woo woo woo as they go past?

Without a specific recording it's hard to be certain, but there are a couple of additional possibilities in addition to the transmission noise as mentioned by AM9 above.

One is that the gap between each car will create vortices in the air, and most of the energy associated with that turbulent air will be dissipated as sound. The sound from these vortices is fairly localised and heard as a sharp whoosh as each inter-car connection goes past you.

Another is the traction inverters, which convert the DC power of the train's onboard power bus into AC for the AC traction motors. These operate at different frequencies according to the train's speed.

All of these sounds will be subject to the Doppler effect, where the tone of the sound will start higher as the train approaches and shifts to a lower tone as it goes past.