Class 450 Traction motors

[LucaZone]

Hiya,

Cna anyone point me towards details about what and why the Class 444 and 450 units make the high pitched whining sound?

Im looking to recreate or record these sounds and want to know what causes them to occur.

Cheers

 

[NXEA!]

well i do know that they've had they're inverters or whatever they're called replaced cos of the heat building up in the underframes cos of the suburban work they do. The low pitched sound when a desiro moves off is made because the driver has put the power on a lower notch until the train begins to move slightly faster which is when the high pitch noise comes into play because he's opened it up fully a few seconds after beginning to leave the station. hope this helps. :P

 

[royaloak]

Nothing to do with the driver, at a stand if we open them up fully we get 100% power showing on the dash straight away for about 10 seconds when it falls off to about 55%, the noise is independant of what we see.

I would think the noise is something to do with the field strength on the motors.

 

[LucaZone]

The low pitched sound when a desiro moves off is made because the driver has put the power on a lower notch until the train begins to move slightly faster which is when the high pitch noise comes into play because he's opened it up fully a few seconds after beginning to leave the station. hope this helps. :P

As above, I read somewhere that this was actually done automatically, independant of the drivers input, due to the heat build up.

Which incidentally I think I witnessed at Guildford a week or so ago. 450004 sizzling in Platform5, requiring a bit of an extinguish before it was allowed to restart its motors.

 

[starrymarkb]

The high pitched noise is the sound of the inverters resonating. Its common to all IGBT traction gear. But while Electrostars, 1995 stock, and others seem to make a constant tone the Desiro seems to oscillate frequencies giving its UFO noise.

IGBT gear always runs hot too, there is a drop of about half a volt over the inverters and with the high currents involved this creates lots of heat and requires forced cooling (ie Fans) - listen to a 1995 stock tube train stopping and you'll hear the fans shutting down when the train comes to a halt.

 

[TheSlash]

Which incidentally I think I witnessed at Guildford a week or so ago. 450004 sizzling in Platform5, requiring a bit of an extinguish before it was allowed to restart its motors.

Ah, that would be when Guildford panel lost the plot. Emergency alarm to all surrounding boxes and juice off from London road, Bellfields, Wood Street and Farncombe.
Phoned the emergency services and told them there was a major incident at Guildford. Surrey Fire and Rescue rolled up with four appliances and more on stand-by.
Ir was only a Line Filter on fire, not much worse than a shoegear fire

I always thought the fan was for the brake resistor?

 

[Juniper Driver]

well i do know that they've had they're inverters or whatever they're called replaced cos of the heat building up in the underframes cos of the suburban work they do. The low pitched sound when a desiro moves off is made because the driver has put the power on a lower notch until the train begins to move slightly faster which is when the high pitch noise comes into play because he's opened it up fully a few seconds after beginning to leave the station. hope this helps. :P

That's not actually correct,the driver does not actually have to start off from a low power notch,although I do from Waterloo,generally it's straight into full power depending on the circumstances.The train electronics take over.You get the noise in any notch and also during braking if the rheostatic brake is operational.The one time the rheostatic brake may not be operational is when the train is slipping,the the pneumatic takes over.

Not sure why they make the sound although I must have been told about 1000 times.

 

[TheSlash]

It's the switching frequency of the transistors

 

[Juniper Driver]

It's the switching frequency of the transistors

Thanks.Good noise though,it gives the trains a bit of character.

 

[ChampsRacing]

As above, I read somewhere that this was actually done automatically, independant of the drivers input, due to the heat build up.

Which incidentally I think I witnessed at Guildford a week or so ago. 450004 sizzling in Platform5, requiring a bit of an extinguish before it was allowed to restart its motors.

Ah yes that was fun to see that pulling into guilford when i was working my 455 i must admit, 75 late and missed my next chessy thankyou very much 450004 :P