Transformer turns high voltage into 480A 3P. This gets output as the 3 phases plus neutral to the switchgear. That’s it. They dont run individual wires from the transformer for each cabinet. That’s why there is a switchgear cabinet to route to cabinets.
900kcmil Al is only 480A. 500kcmil is 350A. why use 2x 500 when 300kcmil will get you 255A each. Which is beside the point. Here is what Tesla uses and how they set things up. This is for an 8 stall site but, again, transformer to switchgear doesn’t change number of wires unless the wiring for each phase is split across multiple wires. Also, 4” conduit is capable of 4 1000kcmil wires.
It's 480V (Volts - electric "pressure") not 480A (Amps - amount of current flow).
really 480 Volts phase to phase, 277 Volts phase to neutral.
I never said or implied wiring was direct from the transformer to the V3 cabinets.
There are
SIX (6) V3 supercharger cabinets at this site, each draws at max 465 Amps per phase.
6 x 465 Amps is 2,790 Amps.
And by NEC article 625 Electric Vehicle Charging System, the breaker and wiring from the switchgear to the V3 cabinet must be sized to handle 125% of that, since it's a continuous load.
While the power company can get away with certain things, since they're under the National Electrical Safety Code instead of the NEC, it won't be that much less.
From the NEC table 310.15(B)(16) - which is for not more than 3 current carrying conductors in a raceway -
1000 kcmil (a.k.a. mcm - mil (thousand) circular mils) aluminum is only good for 500 amps using 90 deg. C insulation.
2,790 Amps / 500 Amps = 5.58, so they'd need 6 (six) 1000 kcmil wires per phase and neutral, (3 + 1) x 6 = 24 in total.
You were right in that 4 1000 kcmil
COMPACT conductors will fit in 4" schedule 40 PVC (Table C.10(A)).
So there's got to be at least 6 4" conduits from the transformer output to the switchgear input.
And that ignores ground wire(s) as well as assuming the utility gets to ignore the 125% factor.
465 Amps x 1.25 = 581.25 Amps from switchgear to V3 cabinets, which won't fit on 1000 kcmil, but will on pairs of 400 or 500 kcmil Aluminum,
AS LONG AS THEY ARE IN SEPARATE CONDUITS. Otherwise there's a derate to 80% of the ampacity rating (Table 310.15(B)(3)(a)).
And there may be a derate based on expected ambient temperatures.
Anyway, it looks like 12 4" conduits on the output side of the switchgear, plus 6 small conduits of about 1.25" or thereabouts.
Anybody know what those small ones are for?
