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Rojony Khatun Author
Rojony Khatun
CalculatorToolsProjectExpert
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Małgorzata Koperska, MD Steven Wooding
Last updated: August 21, 2025

Line to Phase Current Calculator: Three-Phase Systems

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line to phase current calculator

Convert three-phase line current to phase current and vice versa in star (Y) and delta (Δ) systems for accurate AC circuit analysis.

three-phase current conversion

The extent of line to phase current correlation assumes a relationship that varies in any of the types of connections in three phases. In the case of star connections, there is equality between the line current and phase current. In the case of a delta connection, the phase current is 3 times the line current. This calculator makes converting between line and phase current easy to do correctly when going through the analysis of AC.

Formula & Table Summary:

Star (Y) Connection: I_line = I_phase
Delta (Δ) Connection: I_line = √3 × I_phase
Conversion (Delta): I_phase = I_line / √3

switch wiring diagram

The Line to Phase Current Calculator assists in changing between line and phase currents in three-phase electrical circuits, which may have either a star (Y) or delta ( D ) electrical system. The line current in a star (Y) connection is the same as the phase current, and with a delta (Delta) connection, the line current is 31/2 times the phase current. Transformer sizing, Motor load analysis, and protection device selection depend on correct conversion. The tool enables engineers, electricians, and students to easily find phase currents based on known line currents or vice versa to aid with balanced and unbalanced three-phase systems. Proper design, load distribution, and safety accuracy on three-phase AC circuits must be achieved through the utilization of such calculations.

switch wiring diagram

ConnectionLine Current (A)Phase Current (A)
Star (Y)1010
Delta (Δ)17.3210
Delta (Δ)34.6420

Frequently Asked Questions - line to phase current calculator:

What is line current in a three-phase system?

Line current is the current flowing through the external lines connecting the source to the load in a three-phase system.

What is phase current in a three-phase system?

Phase current is the current flowing through each individual phase winding or branch of a three-phase system.

How do I convert line current to phase current in a star (Y) connection?

In a star connection, line current equals phase current: I_line = I_phase.

How do I convert line current to phase current in a delta (Δ) connection?

In a delta connection, phase current = line current ÷ √3 and line current = phase current × √3.

Can this calculator be used for AC circuits?

Yes, it works for three-phase AC systems using either star or delta connections.

Why is the √3 factor used in delta connection calculations?

The √3 factor arises from the 120° phase difference between phases in a three-phase delta system.

Is the line current always equal to phase current?

No, only in star (Y) connections is line current equal to phase current. In delta, line current is √3 times phase current.

Can I use this calculator for unbalanced loads?

It is primarily for balanced three-phase systems; unbalanced loads require separate phase analysis.

Why is converting line to phase current important?

It helps in sizing conductors, protective devices, and analyzing load distribution in three-phase circuits.

How can I verify the calculation?

Compare with Ohm’s Law and the known voltages/impedances of the phases; line and phase currents should match the connection type.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.