|
Post by Christopher J on Oct 12, 2005 15:00:49 GMT
1. Why is the trains energy destroyed as heat by the on-board braking resistors? Wouldn't it be much better to use the energy to charge the Trains batteries instead?
2. I was on the Northern Line about a month ago and I opened one of the windows at the end of the car as the train stood at Tottenham Court Road, I stuck my head out and I was hit by a very intense heat (it was hot enough underground!) coming from somewhere underneath the Train- was this the heat generated by the braking resistors?
Thanks
|
|
|
Post by igelkotten on Oct 12, 2005 15:22:27 GMT
1. Why is the trains energy destroyed as heat by the on-board braking resistors? Wouldn't it be much better to use the energy to charge the Trains batteries instead? Originally, traction control equipment wasn't as advanced as it is today. There were experiments with setups such as the one you describe, but they ended up being very bulky, fragile and expensive for the most part. And you would still need a resistor bank to take care of the braking current if the battery was full and couldn't accept more charging. Likewise, the energy generated by braking a train is far more than what most batteries can hold, so if you wanted to go all-battery, you would need to lug around a huge and heavy set of accumulators. Remember, until recently, most batteries used in trains used iron, lead and nickel as their electrodes, so a battery was essentially a solid lump of heavy metal with some acid sloshing around. A more common way of utilising the brake energy was to use the resistors as heating grids for the ventilation, and only a small supplemantary air heater for use when the train was at a standstill. Common in germany and Switzerland, for example. Another problem is that the current generated by rheostatic braking isn't especially "clean" -it has peaks and dips and so on, which means that you would have to install a series of capacitators and filters if you would want to use the current for anything useful, without risking damage to other onboard equipment. Nowadays, the trend is to use regenerative braking, where the current generated is fed back into the third rail or catenary, enabling it to be used by other trains on the same section. 2. I was on the Northern Line about a month ago and I opened one of the windows at the end of the car as the train stood at Tottenham Court Road, I stuck my head out and I was hit by a very intense heat (it was hot enough underground!) coming from somewhere underneath the Train- was this the heat generated by the braking resistors? Thanks Probably. While the 95TS is supposed to use regenerative braking, sometimes the regen fails and you have to use rheostatic braking as a fall-back. Likewise, for control circuitry reasons, it is best to always have a small amount of braking to be rheostatic. I am no expert on the 95 TS, so others will have to fill in here, but other parts that can get warm to bloody hot are the traction converters, which on some types of train are actually liquid cooled. Compressors that run for a while also tend to get hot, since the compression of the air creates a lot of heat which has to be dissipated somehow. Hope this was of some use! /Igelkotten
|
|
Colin
Advisor
My preserved fire engine!
Posts: 11,309
|
Post by Colin on Oct 13, 2005 0:00:09 GMT
The batteries are charged by taking a feed (though altered somewhat) off the traction current.
As for heat under the train - don't forget also that the brake blocks will get warm, as well as the metal wheels running on metal tracks.
|
|
|
Post by q8 on Oct 13, 2005 3:10:45 GMT
The batteries are charged by taking a feed (though altered somewhat) off the traction current. ------------------------------------------------------------------------
Now that surprises me somewhat. Batteries used to be charged in two ways. On the older stocks (Q) they were charged via trickle charger from the juice. On stocks with an MG/MA that charged the batteries, when running, from the windings.
Do not these modern solida state lighting wotnot's have the power to charge a battery then?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 13, 2005 3:45:35 GMT
Time for a 'technical' explanation then! Basically (and I'm sure Solidbond will correct me here!) the current passes through the motors to the alternator, from where it is reduced down through various components to various voltages, one of which is 50vDC which charges the batteries. See the diagram below from the C stock training manual (which I'm actually quite getting into now! ) Solidbond could post a long ramble with the full details if required, but please spare us that! ;D
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 13, 2005 5:27:22 GMT
It's been a few years since I've seen the C stock MA diagram, but the "Smoothing Resister" is something I can't recall seeing before.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 13, 2005 6:10:24 GMT
Alan have you got a larger diagram, i've always wanted to know how (on the electrical circuit side) Trains work...
I've just realised how much time i spend on my electronics coursework... i completely understand that circuit....
|
|
Colin
Advisor
My preserved fire engine!
Posts: 11,309
|
Post by Colin on Oct 13, 2005 11:00:23 GMT
The batteries are charged by taking a feed (though altered somewhat) off the traction current. ------------------------------------------------------------------------ Now that surprises me somewhat. Batteries used to be charged in two ways. On the older stocks (Q) they were charged via trickle charger from the juice. On stocks with an MG/MA that charged the batteries, when running, from the windings.
Do not these modern solida state lighting wotnot's have the power to charge a battery then?Which is why I put "altered somewhat" in brackets!!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 13, 2005 12:07:17 GMT
It's been a few years since I've seen the C stock MA diagram, but the "Smoothing Resister" is something I can't recall seeing before. Im surprised, you have seen every other piece of equipment that has a pornograhpic reference!! ;D Whats that about the trainline air is a mans brake? Because it has a bigger cock than the Main Line Air?? ;D
|
|
|
Post by q8 on Oct 13, 2005 15:30:14 GMT
They used to teach us (officaily too) that ' All cut-out cocks are like your own'....If it's up, it's in...if it's down, it's out!!'
|
|
|
Post by Dstock7080 on Oct 14, 2005 17:31:06 GMT
They used to teach us (officaily too) that ' All cut-out cocks are like your own'....If it's up, it's in...if it's down, it's out!!' Thoughts of the long gone Bob MALIN (Trainsmans Inspector) come to memory with that phrase! With his "tick & tock!" "you know- tick & tick!" still dumbfounded as to the answer, he would gleefully give you the answer as- "RPA- tick & tock! doh!!"
|
|
|
Post by q8 on Oct 14, 2005 17:40:45 GMT
Oh Bob Malin. What a character. I knew him as a driver as well. Nice enough guy but always treated life as a joke. It was he who told me of the never-implemented plans for the grand stock re-shuffle that was to have taken place if the 'C' stock had not been ordered. As a driver he used to tear about all over the shop.
As a stock instructor (old name) he used to hear all sorts of stuff in the grapevine. One time when he was telling new guys about coupling up and explaning how to put jumpers in on a 'Q' stock or shed jumpers, a trainee asked what happened if you could not get it in the hole. Quick as a flash Bob said 'Put a bit of hair round it''
They used to have a base under the stairs at Hammersmith westbound. I assume from the previous post that he is no longer with us.
|
|
|
Post by piccadillypilot on Oct 14, 2005 19:24:27 GMT
Oh Bob Malin. What a character. Yeah, good bloke. Passed me out for Motors. Met him a couple of times on Stock Training as well.
|
|