Why do the three phases matter?
The meter shows about 55 kW in total, well below the limit. But on one of the three phases, the current is close to the fuse.
Four of the cars charge on a single phase, and all four are on the same one.
The questionHow can one phase be full while the total is fine?
16 A on each of three phases
16 A on a single phase
32 A on a single phase
the example connection, the same on each phase
Computed with 230 V per phase. The fuse protects each phase on its own, so each phase has its own limit.
A composed example with a 125 A fuse per phase: the building draws 25 A on each phase, two three-phase cars 32 A, four single-phase cars 64 A, all on L1. L1 is at 97% while L2 and L3 have room.
Why some cars use one phase
The decides how many phases a car uses. Some cars charge on one phase only, others on two or three. A single-phase car at 16 A draws 3.7 kW, all of it from one phase.
Two remedies
- . Charge points are connected in turns: the first with L1 first, the next with L2 first, the next with L3 first. Single-phase cars then spread over the three phases.
- Per-phase control. The controller counts every phase separately and lowers only the charge points that load the full phase.
Connection rules in some countries also limit how unevenly the phases of a connection may be loaded, which makes both remedies common practice.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
A single-phase car charges at 16 A. What power does it draw?
230 V × 16 A is about 3.7 kW, all from one phase.
What does phase rotation do?
Each charge point starts on a different phase, so a single-phase car lands on L1, L2 or L3 depending on where it parks.
Why can one phase be full while the total load is below the limit?
The total adds the three phases, but the protection works phase by phase.
- Onboard charger The converter in the car that turns AC from a wallbox or public AC charger into DC for the battery; its rating limits AC charging power. eMobility and EV basics, stop 04 Glossary
- Phase rotation Connecting charge points in turns, starting on L1, L2 or L3, so single-phase cars spread evenly over the three phases. Glossary