In the old days they used a hewittic mercury-arc Rectifier, to convert electricity from ac to dc. I would love to know why they had to do this!
As far as I know, trolley bus motors are AC motors. AC power is much easier to handle than DC, which is why all the world's power grids are AC. But if you're transmitting power through an underwater cable, like we do through the Cook Strait cable here in NZ, you have to convert it to DC and back to AC at the other end. Two reasons. The cable behaves like a capacitor, with the conductor as one plate and the sea water as the other, and the insulation as a dielectric. AC power would leak away. Also the radiated power would interfere with navigation equipment on ships.
It can. See the link below.....
