what takes place during a load bank test?

[truckman060473]

on the power hour series dvd it shows a class 56 on a load bank test. it is on normal rails and revving it's pants off but not moving. i was just wondering if they re-route the cables from the alternator to a "dummy" resistive load or something as it obviously cant be connected to the traction motors or it'd attempt to move off!

 

[royaloak]

Yes you got it, the electricity is routed through resistors and dissipated as heat, these resistors also load the engine simulating a train to check that everything is working and calibrated properly.

 

[truckman060473]

well it must be one hell of a device! i have seen the resistor used when a mechanic puts a test on a car battery (drop load test) so the resistive windings used for the train test must be HUGE and are they fan cooled?

 

[DaveNewcastle]

Yes, they are. They're manufactured in all sizes for generators and power plants of a wide range of power outputs. Most have both resistive and inductive loads. There a series of larger loads which are built into standard shipping containers and have power ratings around the 5 MegaWatt area. And with VERY powerful blowers to dissipate the energy!

 

[royaloak]

Saw one in use at Doncaster once with a 58 under full load, just the thought of all that power, the heat haze above the load bank and the noise of the fans scared the sh*t out of me.
Anyone with a mechanical or electrical background will appreciate it more.

 

[Kingfisher200262]

on the power hour series dvd it shows a class 56 on a load bank test. it is on normal rails and revving it's pants off but not moving. i was just wondering if they re-route the cables from the alternator to a "dummy" resistive load or something as it obviously cant be connected to the traction motors or it'd attempt to move off!

The other way of doing this kind of test is with a "rolling road". Here's one in China, with an ability to test a Co-Co (or in this case Bo-Bo-Bo) loco at UP TO 400 km/hr!!

I've seen it in use on a freight loco behind bullet-proof glass, but I'm still looking for volunteers for witnessing the high speed test!

 

[truckman060473]

why the bullet proof glass? is it incase the worst happens and a traction tyre fractures and self destructs and bits of metal are thrown out at insane speed?
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to give someone not too familiar with electrics some idea of this load bank it can be explained a bit like having a few thousand "bars" of those old type electric fires and wiring enough of them in series (daisy chained) to handle the alterator's voltage. then banks and banks of the above would need to be added in parallel (like switching on lots of light in a house) until it is pulling the same current as the 6 traction motors! a cooling fan behind all this and you can imagine the heat blown out. if one of those fire bars is 1000 watts and the alternator can produce say 5MW then it would require 5000 fire bars connected up! it's an incredible amount of energy