Overhead Catenary Cables to Charge Electric Lorries.

And do not make the vehicle class 1 !

Indeed!

Taking the  commutating pantograph and DC bus idea further, and making those pairs of diodes totem poles of high power FETs, you can then also push power back into the line or take it out, as suits for example during braking.

Now I like that idea!

So if we wanted  to use railway like voltages, do 25KV FETs that can switch hundreds of amps exist?

My original (trolley bus) very rough reckoning figured that a 400V 3-phase system might do (part of the attraction being that using 'off the shelf' DNO 11/0.4kV transformers would be much more economic than any specials (e.g. the old 650V d.c. system) and LV overheads would be much more acceptable over public highways than HV ones). To match the output of a conventional diesel bus engine we should need less than 100A/phase - which I reckoned a pantograph should cope with. Indeed if there was a small battery on-board, the overhead line system need not ever have to supply the peak load - but just a little over the average - which of course would be significantly lower - making the numbers even more palatable.  Trucks of course are larger/heavier than buses - but not hugely so - a factor of two or three perhaps rather than tens, so perhaps a similar approach might still be workable.


  - Andy.

Dumb question here - with a trolley bus (which doesn't have rails), how is the return path for the current provided?

wallywombat:

Dumb question here - with a trolley bus (which doesn't have rails), how is the return path for the current provided?

Easy - two overhead wires.  But that means a simple pantograph won't work.  You need two spring loaded arms, each hooked onto one wire.