[Weter]

Let's make a kind of summary:

DC
Total manual control, with separate, partially-independent levers.
This can be seen on early, or mid - 20-th century freight locomotives.
Giving variety for ways to drive trains with variable masses and lengths.

Sequential control, direct or indirect: the sequence of switchings is being hard-programmed by eccentrics, assembled on controller's shaft, with specific phase-shift between each other.
This is used for metro, commuter trains, where very frequent throttle/braking changes are needed, but any fault is unacceptable. Also, suitable for passenger locomotives, where train's weight is almost constant, while controller's operations are quite standard (track grades don't affect driving as much, as with long freight trains)

Automatic control, where driver sets only target arrangement, while actual switching is controlled by current's magnitude - more fault-proof variant of above design.
The natural disadvantage here - typical inability to quickly notch-down, but only through setting driver's control handle to zero position, then setting a new notch. Sometimes, setting control handle takes effect in form of partially disassembling the circuitry, however it is unwanted most often, because of following dashes, caused by great voltage/current changes.

AC
As transformer's regulation gives wide range of voltage, the design, similar to sequential variant above prevails.

Diesel-electric with contactor control of DC traction motors.
After 1950-th, mostly automatic field weakening steps transition is used. Motors are most often connected constantly-parallel.

[Fablok]

@Weter

He's on his way here, so he changes positions pretty quickly. But from position 0 to 28 it runs on starting resistances in series. At 0:06 there is a characteristic sound that enters the 29th position. The motors are then in the non-resistance position, the fans turn off and it starts to shunt. And then the same in parallel position. In this EU07, the left ammeter is from the series group and the right one is from the parallel group. Only the one on the right has a hide tip that's best seen on the big screen.

https://www.youtube....h?v=ygEKMI4pwWM

[Fablok]

Ok here is another film showing EU07 run. On picture are descriptions about these lamps. Simply - blue ( loco is on idle) orange - loco is on resistors none - loco is on shunt or non resisting notch. In rar is typical consist with EU07 and cars. Everything is in zip. This eng is not fully OR made du to lact ot this abillities that we talking about here. So Rise te pantograps , hit V and than drive. This is how we "simulated" this circuits. only those ammeters :/

https://www.youtube....?v=yejjtqKkjGw

https://i.ibb.co/28RzCqH/Nowy-Obraz-mapa-bitowa.png

Attached File(s)

•  PKP_SET.zip (53.74MB)
  Number of downloads: 6

[darwins]

Weter, on 30 August 2023 - 09:51 AM, said:

DC

Automatic control, where driver sets only target arrangement, while actual switching is controlled by current's magnitude - more fault-proof variant of above design.

An important thing missing from this type of control in OR is that it can only "notch up" it can not reduce target power to a lower level. To do that the driver must move the control to OFF first and then move to a lower setting.

[Weter]

Hello.
In general, You are right: that's because main controller's shaft can rotate only forward, so for setting a notch, which is lower, than currently set, it have to perform complete turn, to pass zero position, then to stop on that new notch (it's being made, as You've said, by returning driver's control handle to zero, then advancing it to new notch) BUT...
On some schemes, field weakening or motor grouping is being made by individually-controlled contractors, so setting one notch down is technically possible, however, in known cases it will cause significant dashes, due to great voltage/current differences.
***
Have added to summary this notation.

[Laci1959]

Weter, on 02 September 2023 - 12:58 PM, said:

Hello.
In general, You are right: that's because main controller's shaft can rotate only forward, so for setting a notch, which is lower, than currently set, it have to perform complete turn, to pass zero position, then to stop on that new notch (it's being made, as You've said, by returning driver's control handle to zero, then advancing it to new notch) BUT...
On some schemes, field weakening or motor grouping is being made by individually-controlled contractors, so setting one notch down is technically possible, however, in known cases it will cause significant dashes, due to great voltage/current differences.
***
Have added to summary this notation.

Hello.

This is very similar to the typical American PCC streetcar control system. I know that the Czechoslovak Tatra factory bought this license. Maybe they also put it in locomotives?

Sincerely, Laci1959

[Weter]

This is usual on trams, metro and commuter EMU.
Tatra trams are known by pedal throttle/DB control.

[Laci1959]

Hello.

60 years ago, MÁV bought a license for electric locomotives designed by four European factories. It has field weakening (4 shunt stages?). A similar type was purchased by the Portuguese and Indian railways. As a train driver with a type test explained, the voltage gives the speed of the DC traction motor, i.e. the speed. The shunt stages increase the current, i.e. the power.
In the CZ-SK version, it is now possible to specify the voltage for each contactor position.

Sincerely, Laci1959

[Weter]

DC motors generate "counter-current". As they accelerate, this results motor cirquit voltage's growth (which is limited by katenery's voltage), but decrease motor's current. At some speed, counter-current will be almost equal to motor's current at given voltage (since power, which is voltage&current proportional, is constant and limited), and no further acceleration will be possible - because voltage can't be increased any more.
"Excitation weakening" makes bypass circuit (by means of stator coil's shunting through resistors), for current to diverge and to grow again, (thanking bypass branch-circuit, where counter-current is absent), which allows further acceleration, by cost of loosing power (=torque=tractive force), though.

In other words, magnetic field of "excited" stator will induce in rotor some current, having opposite direction, which will be as greater, as faster rotor will rotate.
This is the reason, why rotor's current will be eliminated quite earlier by this counter-current.
Now, we are decreasing the stator's exciting current, by directing some part of it to bypass stator's coil (how much, will be determined by amount of resistance in bypass circuit; in video above, we have six steps of resistance). Magnetizing of rotor will now be less, as stator's magnetic field is weaker, so rotor current will grow again, decreasing motor's voltage, which will allow further acceleration. That's just balance point's shifting.

[Fablok]

https://i.ibb.co/rwBLq4V/polaczenia-silnikoweu07.jpg


Start control
As it was mentioned earlier, the locomotive driver starts the locomotive using the driving controller. By moving the shaft handle of the directional controller to the "FORWARD" or "BACKWARD" position, the reversing switch contacts are switched according to the selected direction of travel.
With this position of the direction shaft, it is possible to turn the main shaft of the travel switch. After switching it to position 1, the line contactor SL 1 (contactor type: SPL 400) is switched on. On the panel, signaling lamps of switched-off line contactors go out and the circuit of the traction motors is closed as a result of the activation of series resistance contactors JS1 and JS2 (type contactors: SPR 400). All segments of the starting resistors are included in the circuit of the traction motors.
Turning the main shaft of the travel controller to position 2 closes the SR1 resistance contactor (contactor type: SPR 400), which results in disconnecting 1 segment of the starting resistors (R1) and increasing the current in the traction motor circuit. The SR1 resistance contactor, by actuation of its normally open auxiliary contacts, prepares the supply of the SR2 resistance contactor coil. The signal lamp "driving on starting resistance" lights up on the dashboard.

Turning the main shaft of the travel controller to position 3 closes the SR2 resistance contactor, which results in disconnecting the next resistance segment (R2) and increasing the current value in the traction motor circuit. The auxiliary NO contacts of the SR2 resistance contactor simultaneously prepare the supply circuits of the SR3 and SR4 resistance contactors.

Turning the main shaft of the travel controller to position 4 closes the SR3 and SR4 resistance contactors, whose coils are powered through the opening contacts of the SR2 resistance contactor, which results in disconnection of subsequent resistance segments. The SR3 and SR4 resistance contactors prepare the supply circuits of the SR5 and SR6 contactors with their normally open auxiliary contacts.

Turning the main shaft of the travel controller to successive positions causes the same as in pos. 4 operation of successive resistance contactors, which causes disconnection of successive segments of starting resistors. In the main circuit, the resistance decreases, the voltage and current supplying the traction motors are increased, and the locomotive's speed increases.

Setting the main shaft of the travel controller to position 28 closes the last resistance contactor - SR30. The power to the coil of the resistive contactor SR29 is interrupted.
Auxiliary contacts of the SR30 resistance contactor supply power to the electropneumatic coils of the bridging contactors JM1 and JM2 (type contactors: SPK 400), which results in direct elimination from the main circuit of the starting resistors previously shorted with resistance contactors, except for the resistance segments shorted by the contactors SR5, SR6, SR25, SR28 and SR30. The bridging contactors also cause disconnection of the JS1 and JS2 resistance series contactors.
All segments of serial drive resistors are shorted (disconnected from the main circuit), the signal lamp "driving on starting resistances" goes out on the desktop. Traction motors are powered directly from the traction network.
In this way, the SERIAL UNRESISTANCE driving position is obtained.

Movement of the main shaft of the travel controller to position 29 is possible if the bypass lever handle is in the 0 position, the start mode switch is set to the "low start" position, all traction motors are engaged and the shaft of the direction controller is set to the "FORWARD" position.
In position 29, the PPR parallel connection auxiliary relay coil is energized. Line contactor SL3 and group contactors of parallel connection JR1 and JR2 (SPK-400 type contactors) are switched on. The JR1 group contactor, with its auxiliary normally open contacts, interrupts the power supply to the electropneumatic valve coils of the bridging contactors J1 and J2, which results in a circuit of parallel connection of groups of traction motors. The resistive contactors SR5, SR6, SR25, SR 28 and SR30 that were previously shorted with the jumper contactor J1 also open.
In the parallel driving system, the motors of each bogie form a group of motors connected in series. The resulting two series motor groups are connected to the main circuit in parallel.
On the dashboard, the signal lamp "driving on starting resistance" turns on again.

Turning the main shaft of the drive controller to successive positions (30-48) causes disconnection of the segments of the starting resistors in the same way as in the case of serial driving, with the difference that the resistance contactors SR1 and SR2 do not close, and all other starting contactors close in pairs. First, the odd-numbered contactor closes, which closes the corresponding even-numbered contactor through its normally open auxiliary contacts.
In position 43, which is the last paralleling position, all resistance contactors, except for the previously mentioned SR1 and SR2, are closed. Thus, all resistors are excluded from the main circuit, which means that the traction motor groups are supplied directly with the voltage from the traction network.
In this way, the driving position of PARALLEL WITHOUT RESISTANCE is obtained.

The R30 resistance contactor closed in the last parallel driving position, similarly as in position 28 (resistance-free series driving), through its normally open auxiliary contacts, closes the AC6 auxiliary contactor coil supply circuit. This contactor enables shunting of traction motor windings, which will be discussed below.
When turning the main shaft of the drive controller in the opposite direction than during start-up, it causes switching on of individual devices and processes in the reverse order. Thus, the resistance of the main circuit increases until the full inclusion of all resistors in the main circuit is achieved - this is the case when the adjuster is set to pos. 1.

As it was mentioned, during the resistance start, the resistance elements heat up. As a result of lowering the voltage on the resistance elements, electrical energy is converted into thermal energy, which is irretrievably lost. Therefore, serial resistance driving and parallel resistance driving should be as short as possible, both for economic reasons of energy consumption and the possibility of overheating of the resistance segments, which may lead to their damage (although they are cooled). The driver should start the engine in such a way as to drive the vehicle as quickly as possible in non-resistance positions, where, as already mentioned, the traction motors are powered directly from the traction network without wasting energy on resistors.

Excitation Weakening (Bypass):
Weakening the excitation of the main traction motor poles, called winding shunting, is possible when driving in non-resistance positions (series or parallel) - the SR30 contactor must be closed and thus the AC6 contactor must be switched on.
The circuits of the traction motor groups include FIA 300 inductive shunts, which are the basic element of the excitation weakening circuit. They are made of a winding placed in an insulating carcass and a core consisting of silicated magnetic sheets. The magnitude of the field weakening depends on the active resistance of the shunt and the field weakening resistors connected to it. The ratio of the total resistance of these elements to the active resistance of the excitation windings of the two traction motors to which the shunt is connected determines the degree of excitation weakening. Two shunts are installed in the discussed locomotives (one for a group of engines) - they are located under the support in specially made boxes next to the battery box.
The excitation weakening is increased by the shunting shaft handle, which has 6 working positions and the 0 position. The SPO 250 electropneumatic contactors are responsible for switching successive resistors into the main pole windings. The higher the position of the shunt shaft handle, the greater the excitation weakening, and thus the higher the motor rotational speed traction. Retracting the bypass shaft handle causes the opening of the bypass contactors, which reduces the weakening of the excitation. Setting the shunt shaft handle to the "0" position causes the AC6 auxiliary contactor coil to be interrupted and all shunt contactors are opened.
All shunt contactors will also open when the travel positioner main shaft is moved from the non-thrust travel position. As a result, the SR30 contactor is disconnected, which causes the power supply to the auxiliary contactor AC6 to be interrupted, and despite the fact that, for example, the shunt shaft lever is in the shunt position, the start-up process is interrupted.
The inductive shunt described here is also included in the compensation circuit for unloading the axles of the wheelsets (anti-skid of the wheelsets).


When changing the position of the main shaft of the travel controller and the bypass shaft during start-up, the driver must continuously control the current values fed to the traction motors so that they do not exceed the settings of the traction motors redundant relays.
The current value of the current fed to the traction motors is read from the ammeters of the motor groups located on the dashboard.