Formula Used
Ohm law for impedance: I = V / Z
Impedance magnitude: |Z| = √(R² + X²)
Impedance angle: θ = tan⁻¹(X / R)
Single phase current: I = V / |Z|
Three phase line current: I = V / (√3 × |Z|)
Peak current: Ipeak = Irms × √2
Design current: Idesign = I × safety factor / efficiency
Power: P = V × I × cosθ
How To Use This Calculator
Enter the circuit voltage first. Select single phase, direct current, or balanced three phase. Choose how impedance will be entered. Use resistance and reactance for rectangular form. Use magnitude and angle for polar form.
Add frequency when the circuit is alternating current. Enter efficiency when losses matter. Use a safety factor for wire, fuse, breaker, or equipment sizing checks. Press the calculate button. The result appears above the form and below the header.
Use the CSV button for spreadsheet records. Use the PDF button for a simple field report.
About Current From Voltage And Impedance
Current is one of the main values in circuit design. It decides conductor size, protection rating, voltage drop, and heating risk. A simple resistance load can use direct Ohm law. Many real electrical loads need impedance instead.
Why Impedance Matters
Impedance combines resistance and reactance. Resistance consumes real power. Reactance stores and returns energy through magnetic or electric fields. Motors, coils, transformers, capacitors, filters, and long cables often show reactive behavior.
Rectangular And Polar Input
This calculator supports both common impedance forms. Rectangular form uses R and X. Polar form uses magnitude and angle. Both describe the same load. The magnitude controls current size. The angle controls phase shift and power factor.
Single Phase And Three Phase Use
Single phase calculations divide voltage by impedance. Balanced three phase calculations include the square root of three. This gives line current from line voltage. It is useful for industrial panels, motors, heaters, and distribution checks.
Advanced Result Checks
The tool also estimates real power, reactive power, apparent power, and complex current. These values help compare load behavior. A mostly resistive load has a small phase angle. A highly reactive load has a larger angle.
Design Safety
Calculated current is not always the final design value. Equipment can run hot. Voltage can vary. Loads can start with surge current. Connections can age. A safety factor helps create a more conservative value for planning.
Export And Documentation
The export options support simple job records. The CSV file can open in a spreadsheet. The PDF report can be shared with a team. Keep these reports with panel notes, equipment schedules, or maintenance logs.
Practical Guidance
Use accurate measured values when possible. Check whether voltage is line or phase voltage. Confirm whether impedance is per phase. Review local electrical rules before final installation. This calculator supports planning, but it does not replace qualified design review.
FAQs
What does impedance mean?
Impedance is total opposition to current in an alternating circuit. It includes resistance and reactance. It is measured in ohms and can have both magnitude and phase angle.
Can this calculator be used for direct current?
Yes. For direct current, set reactance to zero. The calculation then becomes simple Ohm law. Current equals voltage divided by resistance.
What is reactance?
Reactance is opposition caused by inductance or capacitance. It changes with frequency. Inductive reactance is positive. Capacitive reactance is usually entered as negative.
Why is three phase current different?
Balanced three phase systems share power across three conductors. Line current from line voltage uses the square root of three. That factor changes the current result.
What is impedance angle?
The impedance angle shows phase shift between voltage and current. A positive angle usually means inductive behavior. A negative angle usually means capacitive behavior.
What is design current?
Design current is the calculated current adjusted by efficiency and safety factor. It gives a more conservative planning value for cables, devices, and protection checks.
Why include power values?
Power values show how the load behaves. Real power does useful work. Reactive power moves between source and load. Apparent power shows total electrical demand.
Can I size breakers from this result?
This result can support early planning. Final breaker sizing must follow equipment data, duty cycle, conductor rating, and local electrical code requirements.