Why does a single-phase car matter for load management?

A single-phase car draws all its current from one phase. Several of them on the same phase can overload it, so sites use phase rotation and count each phase.

Explained in

Load management · Stop 05Why do the three phases matter?Three-phase and single-phase cars, unbalanced load and phase rotation: why load management has to count per phase, not only in total.
  • Phase rotation. 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. OCPP lets a charger report this wiring order for each connector.
  • Per-phase control. The controller counts every phase separately and keeps each one below its limit, as this one does. OCPP limits in amperes apply per phase, not to the sum of all phases. It protects the fuse, but it cannot use the room on L2 and L3 while every car also loads L1.
From “Two remedies”, stop 05

Terms

  1. OCPPOpen Charge Point Protocol: the open protocol between a charger and its operator's backend.
  2. Phase rotationConnecting charge points in turns, starting on L1, L2 or L3, so single-phase cars spread evenly over the three phases.
  1. What is load management?Load management keeps many chargers below the limit of one connection by dividing the available power. Cars that stand for hours still get the energy they need.
  2. What is the difference between static and dynamic load management?Static load management gives each charge point a fixed share. Dynamic load management measures the building and gives the chargers whatever room is left at each moment.
  3. Can the grid operator limit my wallbox?In Germany, non-public charge points above 4.2 kW put into operation since 2024 count as controllable devices. The grid operator may reduce them temporarily to prevent overload, but at least 4.2 kW remains.
  4. What does an OCPP charging profile look like?A SetChargingProfile message with a purpose (ceiling, default or one session), a kind, and a schedule of periods with a limit in amperes per phase or watts. The deep dive reads the profiles of one morning and the meter value that shows the car following.
  1. Open Charge Alliance: OCPP 1.6 edition 2 (2017), section 2 Terminology (phase rotation), section 7.12 ChargingRateUnitType (amperes per phase, 230 V) and the ConnectorPhaseRotation key; free download. https://openchargealliance.org/download-ocpp/. Checked 13 Oct 2026.
  2. Open Charge Alliance: OCPP 1.6 edition 2 (2017), section 2 Terminology (phase rotation), section 7.12 ChargingRateUnitType (amperes per phase, 230 V) and the ConnectorPhaseRotation key; free download. https://openchargealliance.org/download-ocpp/. Checked 13 Oct 2026.