Great information. Thanks. That really puts some context on it for me. So around 1000A at 4kV on the main bus
. I used to work for the tramways and the large articulated trams weighed 40 tonnes and drew maximum 800A from the 600VDC. You are talking an order of magnitude larger, so around about what our substations were putting out (could handle four or five trams at once on a "section" of overhead).
They are really not that impressive. In the early days it was done with massive rotary converters. It was scary to walk around them while they were running. Notice the limited use of guard-rails.
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These were last run back in the 80's. There were only three locations in the world still running them at the time. Bombay, Calcutta, and Melbourne, Australia. What was really scary was switching the knife switches on the DC distribution wall. That was done using essentially a broom handle with a hook on the end.
Eventually they moved to mercury arc rectifiers, then solid state.
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The basic diodes we used in the substations are "hockey puck" diodes, around 4" diameter and 1.5" thick. They were connected in parallel to achieve the necessary current capability. Connection is made by clamping them between large heatsinks. Heatsinks generally end up being live.
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Sounds similar to what our substations were like. Judging by the size I think they have built in plenty of thermal margin in the design
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Yes, significant heatsinks. Our trams use 2000A hockey puck SCRs. I have one at home somewhere. Good paperweight.
Apologies for the digression, but I hope people find it interesting
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