Calculate sequence current, voltage, or impedance from any two values using positive sequence voltage and impedance in V, Ω, and A units.

Use the positive-sequence phase voltage across the entered impedance, with a consistent RMS or peak basis. Optional angles default to 0°. This does not derive sequence components from three-phase measurements.

Phasor angles (degrees)

Sequence Current Formula

The sequence current calculation uses Ohm’s law for the positive-sequence network. Select the quantity to solve for and enter the other two magnitudes. The default angles are 0°; optional angle fields support the corresponding complex phasor relation.

I₁ = V₁ / Z₁
  • I1 = sequence current, usually in amperes (A)
  • V1 = positive sequence voltage, usually in volts (V)
  • Z1 = positive sequence impedance, usually in ohms (Ω)

To solve for the other variables, the calculator rearranges the same formula:

V₁ = I₁ × Z₁
Z₁ = V₁ / I₁
  • Calculate sequence current: if you enter positive sequence voltage and positive sequence impedance, the calculator divides voltage by impedance.
  • Calculate positive sequence voltage: if you enter sequence current and positive sequence impedance, the calculator multiplies current by impedance.
  • Calculate positive sequence impedance: if you enter positive sequence voltage and sequence current, the calculator divides voltage by current.

Common Unit Conversions for Sequence Current Calculations

The formulas use base units: volts, ohms, and amperes. If you enter kV, mV, kΩ, MΩ, mA, or kA, the value is converted before the calculation.

Quantity Unit Base-unit equivalent
Voltage 1 kV 1,000 V
Voltage 1 mV 0.001 V
Impedance 1 kΩ 1,000 Ω
Impedance 1 MΩ 1,000,000 Ω
Current 1 mA 0.001 A
Current 1 kA 1,000 A

Positive Sequence Values and What They Mean

Term Meaning Used in the calculator as
Positive sequence voltage The balanced voltage component with normal phase rotation. V1
Positive sequence impedance The impedance seen by the positive sequence network. Z1
Sequence current The current component calculated from the positive sequence voltage and impedance. I1

Example Sequence Current Calculations

Example 1: Calculate sequence current

You have a positive sequence voltage of 480 V and a positive sequence impedance of 6 Ω.

I₁ = V₁ / Z₁
I₁ = 480 / 6 = 80 A

The sequence current magnitude is 80 A. Its angle depends on the voltage and impedance angles; with both set to 0°, the current angle is 0°.

Example 2: Calculate positive sequence impedance

You have a positive sequence voltage of 13.8 kV and a sequence current of 2 kA.

First convert the values to base units: 13.8 kV = 13,800 V and 2 kA = 2,000 A.

Z₁ = V₁ / I₁
Z₁ = 13800 / 2000 = 6.9 Ω

The positive sequence impedance is 6.9 Ω.

FAQ

What is sequence current?

Sequence current is a component of current used in symmetrical component analysis. In this calculator, it refers to the current associated with the positive sequence network, found from positive sequence voltage divided by positive sequence impedance.

Why does impedance have to be nonzero?

The current formula divides by impedance. If impedance is zero, the calculation would require division by zero, which is undefined. For the impedance formula, current must also be nonzero because impedance is found by dividing voltage by current.

Should I use line voltage or phase voltage?

Use the positive-sequence voltage across the impedance, with the same phase reference and RMS or peak convention throughout. If the positive sequence impedance is given per phase, use the corresponding phase positive sequence voltage. Mixing line voltage with per-phase impedance can give a result that is off by a factor related to √3.