The Anonymous Widower

Would Batteries Help Voltage Change-over In A Dual Voltage Train Or Tram-Train?

Battery Power And Tram-Trains

Consider.

• The Class 399 tram-trains in Sheffield can work on both 25 KVAC and 750 VDC overhead electrification.
• Their German cousins in Karlsruhe can work on both 15 KVAC and 750 VDC overhead electrification.

In Karlsruhe, there is a ceramic rod between the two overhead cables with different voltages and the pantograph rides across. I suspect that clever power  electronics on the tram-train measures the voltage and converts it automatically to that needed to power the tram-train.

I haven’t been able to see how Sheffield connects the two different voltages, but I wouldn’t be surprised if a similar system with a ceramic rod is used.

Look at this picture, I took of a Class 399 tram-train in Sheffield.

Note the BATTERY CHARGE socket to the left of the car number.

Why would an electrically-powered vehicle need a battery?

I suppose it could be to start up the tram-train in the morning and raise the pantograph.

But could it also be for emergency power, to move the tram-train short distances, such as in depots or to assist the vehicle through the dead sections, where the power supply changes from one voltage to another?

The Class 399 tram-trains ordered for the South Wales Metro will also have to cope with discontinuous electrification. So is the technology needed for this already installed in the tram-trains in Sheffield?

Battery Power And Dual Voltage Trains

Suppose you have a train like a Class 378 or Class 700 train, that can run on both 25 KVAC overhead  and 750 VDC third-rail electrification.

Third-rail trains with contact shoes deal with discontinuous electrification all the time.

If a dual-voltage train had a battery that could take it say two hundred metres, then I believe that voltage changeover could be simplified and speeded up.

I have watched Class 717 trains change voltage at Drayton Park station and what changes would a limited battery capability make.

The third-rail electrification would stop several metres short of the station and would be removed in the station itself.

Going towards Moorgate, this would be the procedure.

• The train would stop in the station as it does now.
• The driver would drop the pantograph, whilst passengers unloaded and loaded.
• The driver would close the doors.
• The train would accelerate away on battery power.
• After a few metres the train would contact the third-rail and the train’s computer would change from battery to third-rail power.

Going away from Moorgate, this would be the procedure.

• The train would automatically disconnect from third-rail power, where that stopped to the South of the station.
• The train would automatically switch to battery power.
• The train  would stop in the station as it does now.
• The driver would raise the pantograph, whilst passengers unloaded and loaded.
• The driver would close the doors.
• The train would accelerate away on overhead power.

The stops should be no longer, than a normal station stop without power changeover.

Conclusion

Batteries may well reduce the time taken to change voltage

February 19, 2019 - Posted by AnonW | Transport | Batteries, Class 399 Tram-Train, Class 700 Train, Class 717 Train, Drayton Park Station, Electrification