Sparks Glowing in the Night

[bill937ca]

Sparks from trains and trams at the Iyotetsu Otemachi station on the Iyotetsu Takahama railway line and Iyotetsu tram lines 1, 2 and 5 in Matsuyama. The trams are 600v and the trains 750v. There are few sparks from the longer 3-car trains, but more sparks from the trams and the orange two-car train. I suspect the trams are supposed to coast through the crossing, power off,  but with the stop being so close this may be hard to do. It seems that some tram operators just ignore the crossing, arcing and all, and draw power through the whole crossing.  Arcing will prematurely burn out current collector equipment.  Video by rokutetsu.

 

 

[kvp]

The 3 car train has two pantographs and they seem to be connected by the train line. This means when one pantograph get too high resistance crossing to and from the isolated section, the other takes the full load instead arcing.

 

For the others, the only clean way would be turning off the main breaker as the lighting and other equipment still needs power even if the cars are not accelerating. (Adding powered graphite resistive bars fixed into isolated rails on each side of the isolated crossing would allow ramping down and back up the current without sparks, but it would need way more maintenance.)

 

ps: These are really nice old trams and trains and imho a great location to model.

[Socimi]

That should be  the way it works in the video, assuming that all the trains pass thru the insulated section while accellerating (with the master controller closed, e.g. with current flowing thru the train circuit).

I've made a simple explaination using two examples:

 

This is the first example, with the 3-car (2 pantographs) 3000 series. For semplification i assumed that all axles were motor.

 

Spiegazione sezione isolata Iyo 3000.bmp

 

Fig.1 - Train approaches the insulated section, where there is no current (aka "dead section"). Pantographs 1 and 2 (not in the picture) are taking power from the live overhead lines.

 

Fig.2 - When Pantograph 1 enters the insulated dead section, it becomes live, as both pantographs are connected via the train main circuit. The train still takes power but from pantograph 2 only. Pantograph 1 (the one in the insulated section) does not take current, but rather it gives it to the section, wich is connected to the ground (via a certain amount of resistors, to prevent short-circuits).

In this case the train may spark very little (especially when te first pantograph enters or the last leaves the dead section) or just not at all.

 

Fig.3 - Same thing as 2, but now pantograph 1 is the one taking power from the live overhead, while pantograph 2 is giving current to the isolated section.

 

Fig.4 - Both pantographs have left the insulated section, wich becomes "dead" again.

 

In all the 4 moments the train can still normally accellerate, auxiliary equipment (compressors, motor ventilation on locomotives...) works and the passenger lights and doors are operational.

 

This is the second example, with the 2 car (one pantograph) 610 series, again for semplification, i assumed all axles were motor.

 

Spiegazione sezione isolata Iyo 610.bmp

 

Fig.1 - As before, the train approaches the insulated section wich is dead. The train is taking power from the overhead lines via it's only pantograph.

 

Fig.2 - When the pantograph gets exactly between the live and dead sections (a space of about 20/30 cm) the current from the live section tries to reach the dead section via the pantograph, but it has not a good path to follow so it arcs. The dead section acutally becomes live for a split second, but as the pantograph fully moves into it, it turns back dead.

 

Fig.3 - The train's only pantograph is in the insulated section. As there is no current, the train cannot accellerate.

In older trains not fitted with backup batteries (such as the old pre-01 series Ginza Line stock) the auxiliaries stop and the lights go out.

 

Fig.4 -  Same as Fig.2, the current from the live section tries to reach the dead section via the pantograph, but it has not a good path to follow so it arcs.

 

Fig.5 - The pantographs has entered the live section so the train recieves power again, and can accellerate normally.

 

 

 

 

Edited July 1, 2018 by Socimi
fixed typos. Drinking Game: take a shot evrytime you read "pantograph"

[Kiha66]

If the crossing is unpowered, how does the interior lighting and such stay on while the car would be coasting over the gap?  Do the cars have some sort of capacitor to store lighting power for such events?

[katoftw]

34 minutes ago, Kiha66 said:

If the crossing is unpowered, how does the interior lighting and such stay on while the car would be coasting over the gap?  Do the cars have some sort of capacitor to store lighting power for such events?

Batteries

[kvp]

The oldest high voltage cars ran from traction power only and the full traction current went through the hand controller. Brakes were straight pneumatic or electric. All trains with a low voltage control circuit and electropneumatic brakes need backup power for the brakes to work in case of main power loss. Loosing the batteries would result in an emergency brake application. On older sets, only the control systems and head/tail lights ran from the batteries which were charged by the motor generator sets powered by traction power. The internal lights and the main motors were high voltage. Newer sets changed the lights to battery power too, even newer ones replaced the MG sets with inverters. The newest sets can even run the air conditioning and to a limited extent the main traction motors from the backup batteries.

 

For newer trains and higher speed lines the pantograph disable and enable operations across traction power boundaries and other dead sections and the switchover between different power systems are fully automtatic thanks to lineside markers. But older rolling stock on low relatively voltage urban lines still use the classic dumb system due to simplicity and the low maintenance costs and reliability that comes with it.