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Charging voltage

Hello everyone,

As Tesla intend to sell cars world wide I just would like to check how versatile the charging is designed.

In north America I understand you get one phase 110V 60 Hz or 220 V for larger appliances. Here in Europe we have 3 phase, 400V, 50 Hz and typically 50 A into the houses, for older systems slightly different systems are installed. Also, you always have 1 phase, 230 V, 50 Hz with 10, 13, 15 or 16 A fuses.

For an efficient charging, you want to use as much power as you can for your car. The more power, the shorter charging duration is needed. With 3 phase, 400V, 50 A can charge the car fully in 45 minutes but your single phase, 230V and 10 A may need 10 hours.

Does anyone know how Tesla S is solving this?

The equation is for watts, not amps (V*A=W for a pure resistive load). When you connect a 3-phase load to a 400V 3~ supply, the load sees 400V only between the phases, L1 to L2, L2 to L3 and L3 to L1 (delta connection). Between the phases and neutral (L1 to N, L2 to N and L3 to N), the load sees only 230V (star connection). 400V*SQ(3) equals 230V so it doesn't matter if the load is delta or star connected, it can only draw 22kW max anyway.

Think of this another way, delta connected (400V) L1 has a load between itself and both L2 & L3. L2 & L3 are 120 degrees out of phase from L1 so you can't draw 32A from both loads as the total would exceed 32A on L1.

Star connected (L1/L2/L3 to neutral you can draw 32A on all loads but the voltage is only 230V phase to neutral.

Norway has a different 3~ system with 230V between phases and 130V to earth. Neutral doesn't exsist in this system and all loads are connected between phases instead. Here we thus have to use both 230V and SQ(3) to compute watts, a 3~ 230V 32A supply is then capable of delivering ~12.7kW instead of 22kW for 400V systems.

I still didn't get it. How come you can't have combined loads between phases go over 32A when both phases have 32A max separate load?

Because L1 has a load between itself and both L2 & L3. If you draw 32A between L1 & L2 and 32A between L1 & L3, the combined load on L1 far exceeds 32A. Not two times 32A though, as the loads are 120 degrees out of phase.

You can draw ~18.5A on both loads simulaneously, that will result in a 32A load on the L1 wire.