EU/EP07/08 How does the brake release button work?

[Atoka220]

As i was taught to drive trains, when the cars' axles exceed 20, i used the brake release button so that the locomotive's brakes aren't applied, only the train brakes (well i do it anyways and control the loco's braking force by pressing and releasing the button keeping the pressure around 1-2 bar)

Now when i press the button and apply the brakes, the loco's cylinders get filled anyways and THEN begin emptying or are only emptied partially, especially in R setting

Is this how it's intended to work and if so, how exactly does it work? Our locos have pedals (or buttons) that when pressed, the loco will not brake whatsoever and i got used to it and being able to play with the braking distances with it

[Isambard Kingdom Brunel]

I thought it was to speed up train break release, after a brake application.

[Królik Uszasty]

Old polish locomotives are equipped w LSt1 distributor valve, which has a bit unusual configuration. The brake regime applies to the flow at the input, instead of output (brake cylinder). Moreover, brake releaser does not dump pressure form steering tank to the atmosphere but to the input tank (6l). It means that the dumped air goes then to... the brake pipe through the small nozzles. So the input pressure rises above brake pipe and equals to the steering tank. If you close releaser to early, the whole air does not leave steering tank-input pair, so there is still difference, when input falls to brake pipe. When this happens, brake applies.

[Atoka220]

So it is indeed intended behavior
I guess i just gotta get used to having that extra brake force and plan with it

Also i'm really interested in how the siódemkas work, any good english read that i can find about them? Such as how is the motor voltage regulated, how dc is converted down and used, different circuits, etc (that is if it's not confidential) 😁
It is withouth doubt my favorite loco series in the sim (maybe because it feels somewhat similar to our v43-s)

[Angelo]

On 6/17/2024 at 4:50 PM, Atoka220 said:

Such as how is the motor voltage regulated, how dc is converted down and used, different circuits, etc

I should check if I have something.

 

The voltage on the EU07 is regulated like in any traditional DC locomotive:

- through resistors, which limit the current: at first they're all included, and one by one they're shorted by contactors;

- by powering the 4 motors in series, so that each one receives ¼ of the voltage, or in a series/parallel combination, so that each receives ½ of the voltage;

- by shunting the field inductors of the motors, so that the magnetic field is reduced, which reduces the voltage generated by the motor itself when the train is running (which goes against the voltage provided by the circuits), so that, at high speeds, the total voltage is increased (difference between the one from the overhead wires, which is more or less constant, and what the motors are generating, since they're turning, which is proportional to the speed).

[Królik Uszasty]

When you use shunting, the field is weakened for this value of electric current, but total field in motor remains... nearly constant and rather dependent on motor speed. Why is that? Overhead voltage (supply) is divived into two parts - voltage loss on resistance in the circuit (typically - motors' resistance after start) and countervoltage generated in motors. However, voltage loss on the motors is not big, it is less than 100 volts for one EE541 motor of EU07 at 600A (!). Compare it to 1500 V on one motor in pair at non resistant position. So the mechanism is like that; 1) you use shunting, 2) field (factor) gradually weakens and decreases countervoltage, 3) it increases difference between supply voltage and countervoltage, so the current flowing through motors (and rotors) increases to compensate that and achieve equilibrium, 4) increased rotor's current and nearly the same field means more torque.

[Atoka220]

Thanks guys
Turns out it actually has nothing in common with our workhorses besides having DC motors 😅

Our machines operate on 25kV 50Hz and i was taught about position switches (with adjustable transformer coil length) and thyristor controls
...so yes, already having DC means you don't need all that fancy hardware, you can just control voltage and current right away

However what i'm surprised is the max allowed current is 600A (750 in high setting) and it sometimes gives me some headaches. Is the reason behind it related to the line voltage being 3kV or it's just a limitation of the loco itself?
Cause one thing i noticed is with a good loco hauling a longer intercity can suck away as much as 2 to 3 kilovolts from our line with a powerful acceleration. And one can even tip the breaker in the substation with a big old v63 drawing nearly 7000A at start 😬

Yea sorry for comparing so much with our AC lines but that's the only thing i have experince with

[Królik Uszasty]

I think that 7000A is on "low" side with voltage between 500 to 1000 V, and 2kV droo is on "high" side of 25kV.

In Poland overhead voltage drop is meant to be about 10% (from nominał 3300V to 3000V, however sometimes power points are set as high as 3500-3600V). Max allowed current 600A is limitation of electric motor, so EU07 can draw up to 1200A and ET22 up to 1800A. The most powerful motors in Poland are on EP09, which have nominal current about 500A and maximal 850A, so it can draw up to 1700A (Bo'Bo' locomotive).