Just curious (not clever enough to work it out) but why are 3 phase chargers more powerful than single phase fed ones?
Is it just that the mains circuits have different capacities or is a 3 phase when rectified more powerful?
I think it is just because a standard house single phase supply is only going to provide a maximum of 10kW to a single circuit using standard components. If one needs a higher power supply it is going to cost a lot and is routinely supplied as three phase to make the best use of the available supply cables and standard components.
Three phase gives you a number of advantages. A typical domestic supply is fused at 100A. So at 240V that limits the maximum rate of power delivery to 24kW. A three phase supply will have three incoming live phases all fused at 100A, giving total capacity of 72kW.
(there are other advantages to a 3 phase supply - such as having the capability to power a load between phases rather than just between phase and neutral, raising the available supply voltage to ~415V. Plus the ability to do cleaver stuff with motors etc. However most of these will not have much impact on car chargers)
Bigger electrical loads of all types are three phase to balance up the currents in the electricity supply. unbalanced loads lead to voltages appearing on the neutral and reduced capacity of transformers/switchgear etc.
So if you have a single load of more then approx. 10Kw, the supplier will want you to you having a three phase supply.
There are two aspects.
1) 3 phase has less copper loss than single phase. 2) 3 phase rectification provides significantly less ripple current than single phase rectification.Normal domestic and light industrial supplies are 100A feeds which give a max of 23/24kW depending on supply voltage
Add one more cable and you could have 69/72kW assuming a neutral is not required.
Yes large machine tools can make this an essential as well, as a friend discovered a few years ago. although you can simulate three phase its not going to allow the power needed when the motor starts etc, in the case of charging a car, this current used to charge it seems very high. Goodness knows what the cost will be, and one assumes it has its own meter. Brian
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