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Wiadomości - DB-47

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1
Mostly passanger trains need that, because there is signficant power draw around 50 - 150A from 3 kV DC OHL to feed carriages with power to charge their batteries, power A/C or heater and feed electric sockets / lights. This current is quite small consumption at travel speeds, however when standing at one place it can cause local overheat of overhead lines, which can in worst case lead to its rupture and teardown. Halving that current by raising second pantograph reduces waste heating power to 25 % (P = R * I^2) which prevents this from happening.

EMUs and all cargo trains pulled by thyristor / IGBT driven locomotives (like ČD 163, Traxx, Taurus 1216) do not require this procedure as their standstill power consumption is much smaller and ammount of taken current raises gradually with increasing speed instead of burning "surplus" power in resistor bank like in for example EU07/201Eo/ČD 181, and so on. Light cargo trains pulled by locomotives with resistive regulation like ČD 181 also do not need both pantographs raised as their power draw at standstill is miniscule. For instance ČD 181 with all auxiliary devices running (fans, both compressors on and 48V DC network convertor) barely draws 50A. However as for what I heard from ČD Cargo locomotive engineers, you are not supposed to exceed current draw 200A per pantograph below 5 km/h, so they raise both pantographs anyways to be sure.

Here in Czech republic this is being done on 3 kV DC routes. On 25 kV 50 Hz routes this is not mandatory as currents are smaller by magnitude and barely exceed 20A at standstill assuming power factor is near 1.

2
Hello everyone,

I noticed one strange thing on ET42 locomotive kind of related to train heating bug I have reported recently. It seems when you raise only rear pantograph, current values on series-parallel and parallel are only half of what they should be. For instance I have rear pantograph raised up, I am driving on parallel notch (38) drawing 400A per motor group, so I would expect 1600A being drawn from overhead lines, but only 800A is being drawn as seen in debug mode. (Sreenshot attachment)

I know, that ET42 has special "granny" mode (which can be activated by Ctrl+F) where you can connect all 8 traction motors into series so you can reach faster resistor-less notch for heavy trains or cruise at low speeds without using resistor notches. Here actually one bug resolves another bug, because there is twice more current being drawn in this "granny" mode, and rear pantograph only halves current, so 0.5 * 2 = 1 and fixes that unless you raise front pantograph.

If my understandment is correct, ET42 has those motor (groups) connections:

All series (8S ; 375V per motor) = S // Which I call in paragraph above "granny" mode
Series-parallel (2P 4S ; 750V per motor) = SP
Parallel (4P 2S ; 1500V per motor)  = P

So I tested all connections and pantograph combinations at 200A seen on traction motors ammeter for both rear and front section and here are the results.

Rear pantograph only:

S: Actual = 200 A ; Expected = 200 A ; OK
SP: Actual = 200 A ; Expected = 400 A ; NOK
P: Actual = 400 A ; Expected = 800 A ; NOK

Front pantograph:

S: Actual = 400 A ; Expected = 200 A ; NOK
SP: Actual = 200 A ; Expected = 400 A ; OK
P: Actual = 400 A ; Expected = 800 A ; OK

Both pantographs

S: Actual = 400 A ; Expected = 200 A ; NOK
SP: Actual = 200 A ; Expected = 400 A ; OK
P: Actual = 400 A ; Expected = 800 A ; OK

As again, I would be happier if I could post those findings written in Polish, however as Czech user it would be tragedy to write in PL or have this processed by Google translator :D , so I will remain posting my finding in English.

Best regards,
David

3
Hello there,

I discovered minor bug when doing some atypical trainsets. I created trainset ET42 + 2xEN57 to try whether you can pull "dead" EMUs or for instance simulate their transport to overhaul repairs or scrapyard. However during tests I discovered, when you brake only locomotive by using locomotive brake or electrodynamic brake and you exceed 100 kN of braking force. Trainset suddenly halts to complete stop as if there was derail. I recorded short private video clip showing also some debug information.



Repro steps:

I. Accelerate to at least 20 km/h
II. Apply at least 100 kN braking force by using locomotive brake or dynamic brake (for instance on ET42 or Traxx)
III. Observe trainset stopping instantly

Trainset used: See attached screenshot


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