electric power query

[ash39]

I've seen some posts on here where people say they can tell if a driver has engaged notch 1/2/3 or whichever, on a diesel engine, presumably as the noise intensifies and it revs quicker,much like pressing an accelerator on a car.
However, can the same be said of electric powered trains? certain emus are very distinctive in sound, and class 91 and 92 locos make a huge noise, although I expect its mostly cooling fans you can hear. The 91 in particular has a distinct two stepped tone as it departs, would this be any louder the more power was applied?
Finally,sorry for all the techy questions! Is car-like traction control utilised in train power application? If not, wouldn't it be a good idea? Applying as much power as each wheelset can take for most efficient acceleration. I'm assuming that a bo-bo locomotive would feed power to all 8 wheels.
Thanks for anyone willing to have a go at explaining all that to me! I'm quite technically minded when it comes to cars but not trains, hence the car analogies.

 

[Nym]

Sorry to be very unspesific, but the answer to all your questions is; "It depends."

There isn't one type of electric traction system.

I can tell the power notches on some EMUs, but that is more to do with the changes in chopper frequency at different speeds.

The class 91 for example uses differnt traction packages to the class 92, where noise you can hear from the 92 will be the switching frequencies this may not be the case for the 91s, I havn't heard enough or put enough research in to comment.

How would you mean car like traction control system, making use of differentials? Differential drive to different axles? Again, it depends on the unit.

 

[Mike C]

Speaking from my own experience with TGVs - it is difficult to tell *exactly* how much power is being requested by the driver, but if you can hear the traction motors, you can roughly judge if they're on a low or high demand. As soon as any power is applied, transformer fans, oil pumps, compressors, motor blowers all kick in and make a lot of noise.

It is also worth noting that TGVs don't have "notches" - it is an infinetly variable power controller - much like the accelerator pedal in a car.

Traction control is used on the majority of rolling stock. Only we call it WSP. Wheel Slip Protection. Does the same thing as TC on a car. The same wheelspeed sensors are used as feedback for Wheel Slide protection (also WSP) which is the equivalent of ABS in a car.

 

[Smudger105e]

Some traction use wheel slip as a method of increasing power onto the rail, class 60s for example use this. They allow the wheels to slip at about 3 or 4% I think, which apparently gives optimum adhesion.

No need for a differential as such on traction as the wheels each side always turn at the same speed as they are the same size and joined together with a solid axle.

 

[ash39]

Thanks for the replies so far

Loco fitter - I'd realised that pairs of wheels are joined by solid axles but Id assumed that all sets of wheels would be powered? Eg, 8 wheels in a bo-ho and 12 in a co-co. Am I wrong or again does it vary?

 

[HSTEd]

Thanks for the replies so far

Loco fitter - I'd realised that pairs of wheels are joined by solid axles but Id assumed that all sets of wheels would be powered? Eg, 8 wheels in a bo-ho and 12 in a co-co. Am I wrong or again does it vary?

In a bo-bo or co-co this is correct, but there have been some unusual configurations like the Cl46 that was co-co with two additional axles that aren't (1co-co1)

 

[ainsworth74]

Loco fitter - I'd realised that pairs of wheels are joined by solid axles but Id assumed that all sets of wheels would be powered? Eg, 8 wheels in a bo-ho and 12 in a co-co. Am I wrong or again does it vary?

On trains you talk about powered axles not wheels, so on a Bo-Bo configuration there would be four powered axles not eight powered wheels. But there can also be trains that have unpowered axles (especially when dealing with multiple units) but sticking to locomotives an example of this would be the Class 46 which is 1Co-Co1 which means that there are four axles per bogie with the outer axle of each being unpowered. Another example would be Class 31 which is A1A-A1A and has the two outer axles on each bogie powered whilst the centre axle is unpowered.

 

[captainbigun]

However, can the same be said of electric powered trains? certain emus are very distinctive in sound, and class 91 and 92 locos make a huge noise, although I expect its mostly cooling fans you can hear. The 91 in particular has a distinct two stepped tone as it departs, would this be any louder the more power was applied?

All you hear when direction is selected on a 91 is blower motors, first the rad blowers, then the rather large and loud motor blowers, they drown any noise. There's no perceivable noise from the converters.