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Post by golfingtrojan on Feb 2, 2016 5:05:37 GMT -5
As a new member i thought i'd try my hand at starting a new thread, and one thing thats always puzzled me over the past few years is the noise that the electrified trains make. Does anyone know what the strange pulsing noise is as a trains pulls in and away from the station? Is it a capacitive noise or some fancy traction engine?
Any info is much appreciated.
GT.
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Post by yv47r on Feb 2, 2016 16:49:09 GMT -5
I can ask a friend who is a driver for Northern Rail at Manchester, he might know although he only drives the older class 323 electric units.
Cheers Paul
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Post by golfingtrojan on Feb 3, 2016 6:25:04 GMT -5
Thanks Paul. Any info on this would be great. Its just one of those things that annoys me as i dont know the answer. I'm greedy when it comes to knowledge :-P
GT
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Post by yv47r on Apr 17, 2016 16:42:16 GMT -5
Hi, sorry I haven't replied to this post sooner but I haven't been able to find much out as my friend been on sick leave for a while.
However from what I have been able to glean different EMUs (electric multiple units) use different types of traction packages that either convert say 25kV AC to a lower kV AC or DC output or convert 650V DC into AC. There are several generations of controllers as to how the voltage and current are converted depending on what technology was in at the time say in the 80s, 90s or 00s. So in effect these traction packages will mean that different EMUs will make different noises when starting away from a station stop or slowing down for one and even when just ticking over. If you really wanted to read more into the different traction package types then a good starting point might well be Modern Railways magazine, which has covered the different types of EMUs and how they operate and the traction packages over the years and so if you are able to access back issues of this mag maybe through a large library or maybe even online this might well give you some idea of the different ones!
HTH cheers Paul
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Post by Daniel Beardsmore on Apr 9, 2023 9:40:30 GMT -5
May as well necro and write something here … Class 319 and 325: the pull-away hum is apparently DC pulse width modulation to reduce motor inrush current. Sometimes you seem to hear something similar from other types but nothing else is anywhere near as distinctive. I never have found out what drive system was used on the 455, 321 etc. I think I even heard a similar sound from a 313 but I assume those are just camshaft-controlled resistance. (Somewhere there was a video on YouTube showing the camshaft control on a British EMU—with the side panel removed from the underframe module—but I never found or encountered it again sadly.) Class 323, 365, 465, 466, 1996 stock etc: the sounds represent the electrickery needed to generate an AC frequency higher than what a high-power thyristor is capable of, as the AC motor speed is determined by the AC frequency. The following video shows something akin to class 323 style (with a very high number of switching patterns) on an oscilloscope, albeit not very clearly: Here's What One of The First VVVF-Inverters Sounds Like (Toshiba PTR-VVVF) (YouTube) “Javworkers” and everything else mid-90s on: still a variable frequency drive the same as 323, 365 etc but different in principle and I have no idea what the sound represents on these. There is no noticeably change in pitch during acceleration, but you have some truly bizarre and very sudden changes in pitch and intensity at speed. As a bonus, something I found recently: Class 87 Tap Changer Demonstration (87035) (YouTube) Tap changers are far larger and far more complex than I expected! |
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Post by Daniel Beardsmore on Apr 28, 2023 14:30:40 GMT -5
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