Class 350 warble whilst accelerating?

• 18 Jan 2014

• #1

102 fan

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Hi

Can anybody tell me what causes the warble on a Class 350 as it accelerates from a station?

Thanks

 

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RailUK Forums

• 18 Jan 2014

• #2

Monty

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It's the AC traction motors, all AC equipped locos/units make this noise. Don't ask me exactly why though.

 

• 18 Jan 2014

• #3

Domh245

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I think that it is the traction equipment, more specifically the Inverter converting the DC supply (which has been rectified from the 25KV AC) into the 3 Phase AC needed to drive the traction motors. It is a similar thing that causes the high pitched whine on electrostars.

 

• 19 Jan 2014

• #4

Kristofferson

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Same thing with 323s I believe, which have the best 3 phase motor sound - they sound like F1 cars when accelerating!

 

• 19 Jan 2014

• #5

Y

YorkshireBear

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It is what i love about AC units. And particularly the 323s and the 350s for me.

 

• 19 Jan 2014

• #6

Domh245

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The 323s have GTOs, which are a bit like IGBTs, but older and not as good. Correct me If I'm wrong, but these can be used to control DC motors as well, for example on the 319s and 456s, which have DC motors, but have GTO controllers, hence the whine when they start up.

 

• 19 Jan 2014

• #7

E

edwin_m

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You could use IGBTs to control a DC motor too if you wanted too. But by the time IGBTs appeared AC motors were practially universal in rail traction.

The GTO can only run at a lower frequency, hence it needs to "hop around" to avoid signalling equipment frequencies which would otherwise be in its operating range. By running at higher frequencies IGBTs can guarantee* not to affect the signalling and also have a simpler control algorithm.

*a gross oversimplification

 

• 20 Jan 2014

• #8

59CosG95

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Domh245 said:

The 323s have GTOs, which are a bit like IGBTs, but older and not as good. Correct me If I'm wrong, but these can be used to control DC motors as well, for example on the 319s and 456s, which have DC motors, but have GTO controllers, hence the whine when they start up.

Click to expand...

But since the 319s and 456s (in fact, all BREL-built EMUs) have DC motors, so they sound as if they're groaning like a grumpy teenager (like myself 2 years ago!), but lots will now get AC motors-the 317 and 455 spring to mind.