Calculate sequence current, voltage, or impedance from any two values using positive sequence voltage and impedance in V, Ω, and A units.
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Sequence Current Formula
The sequence current calculation uses Ohm’s law for the positive-sequence network. Enter any two values, and the missing value is calculated from the same relationship between positive sequence voltage, positive sequence impedance, and sequence current.
I_1 = V_1 / Z_1
- 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:
V_1 = I_1 * Z_1
Z_1 = V_1 / I_1
- 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.
I_1 = V_1 / Z_1
I_1 = 480 / 6 = 80 A
The sequence current is 80 A.
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.
Z_1 = V_1 / I_1
Z_1 = 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 voltage that matches the impedance model you are using. 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.
