Formula and meaning
Convert charging power into current per phase, or calculate power from current, voltage, phase count, and power factor.
Single phase: P = U · I · cos φ · Three phase: P = √3 · U · I · cos φ
E-mobility · AC power
Wallbox Power and Current Calculator
Convert single- and three-phase AC charging power and current into each other using voltage and power factor.
EVAC/DC
02
Results
ƒ(x)
Set the inputs and run the calculation.
Context
At 400 V, three phases, and cos φ = 1, 11 kW is about 15.88 A per phase and 22 kW is about 31.75 A.
The model considers a balanced AC connection with sinusoidal quantities. The calculated current is not an automatic recommendation for protective-device rating or conductor cross-section. Installation design is separate.
Inputs and method
Wallbox power and phase current
Convert AC charging power and current for single- or three-phase connections.
Inputs
Voltage, phase count, current or power and cos φ define the calculation.
Phase count and cos φ determine how power is distributed among conductors. The calculated current must then be checked against continuous rating, cable length, installation method and protection.
Calculation
Single phase P = U·I·cosφ; three phase P = √3·U·I·cosφ. Current is not an automatic cable or protective-device design.
Example
400 V, three phases and 11 kW at cosφ = 1 give about 15.9 A per phase.
Sources and limits: AC power equations; design installation to applicable electrical and grid-operator rules.
Wallbox power and phase current in detail
Convert AC charging power and current for single- or three-phase connections.
What does this quantity describe?
Electrical equations link voltage, current, resistance, power and energy. They describe a defined operating point and require matching quantity types and consistent units.
Formula and variables
Single phase P = U·I·cosφ; three phase P = √3·U·I·cosφ. Current is not an automatic cable or protective-device design.
Choose the inputs correctly
Voltage, phase count, current or power and cos φ define the calculation. Phase count and cos φ determine how power is distributed among conductors. The calculated current must then be checked against continuous rating, cable length, installation method and protection.
How to use the calculator
Choose single- or three-phase connection, enter grid voltage and either the desired charging power or phase current, and add the power factor cos φ. The calculator solves for current or power depending on the selected target.
Worked example
400 V, three phases and 11 kW at cosφ = 1 give about 15.9 A per phase.
Understand the result and units
Phase count and cos φ determine how power is distributed among conductors. The calculated current must then be checked against continuous rating, cable length, installation method and protection. A calculated current is not an automatic cable or fuse approval. Heating, continuous duty, phase angle, harmonics and the real load curve may require additional checks.
Voltage in volts, current in amps per phase, power in kilowatts; cos φ is dimensionless (1 for a purely resistive/ideal load).
Typical applications
Converting between a target charging power and the resulting phase current when planning a wallbox, for example to check whether an existing supply or planned protection device can support the desired power.
Assumptions, limits and common mistakes
AC power equations; design installation to applicable electrical and grid-operator rules.
Common mistake: Don't use the calculated current directly as a cable size or fuse rating – it is purely a value derived from the power equation. Installation method, ambient temperature, cable length and applicable electrical/grid-operator rules determine the actually permissible protection.
Frequently asked questions
Why is current per phase lower with three phases than with one?
At the same power, three-phase current is shared across three conductors instead of one; per-phase current is therefore lower by a factor of √3 than single-phase at otherwise equal values.
What does cos φ = 1 mean?
It describes an ideal, purely resistive load with no phase shift between current and voltage; most modern chargers are close to this, though real values can differ slightly.
Is this calculator enough for a wallbox electrical design?
No. It only gives the power-current relationship; protection, cable sizing, earthing and grid-operator registration must be planned by a qualified electrician per applicable standards.
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