Line and Phase Voltage/ Currents

    Let's break down the concepts of line and phase in electrical systems. 

Understanding Line and Phase

• Line Voltage: The voltage measured between any two line conductors in a three-phase system.
• Phase Voltage: The voltage measured between any one-phase conductor and the neutral in a three-phase system.
• Line Current: The current flowing in any line conductor in a three-phase system.
• Phase Current: The current flowing within a single phase of a three-phase system.

Study Notes

• Star (Y) Connection: In a star connection, one end of each phase winding is connected to a common neutral point. Phase voltage is measured between a line and neutral.
• Delta (Δ) Connection: In a delta connection, the phase windings are connected end-to-end in a closed loop. There is no neutral point, so phase voltage and line voltage are equal.
• Relationship between Line and Phase (Star):
• Line Voltage (Vl) = √3 * Phase Voltage (Vph)
• Line Current (Il) = Phase Current (Iph)
• Relationship between Line and Phase (Delta):
• Line Voltage (Vl) = Phase Voltage (Vph)
• Line Current (Il) = √3 * Phase Current (Iph)

Short Notes

• Line: Conductors carrying voltage between phases.
• Phase: A single voltage source in a three-phase system.
• Star (Y): Has a neutral point. Line voltage is higher than phase voltage.
• Delta (Δ): No neutral. Line and phase voltages are the same.
• Calculations: Remember the √3 factors for conversions.

Point-Based Notes

• Line quantities are between two phases, and phase quantities are between a phase and neutral.
• Line voltages and currents exist in both star and delta connections.
• Phase voltages and currents are primarily relevant in star connections.
• Star connections are often used for long-distance transmission.
• Delta connections are often used for motors.
• Phase voltage (Vph) is line voltage (Vl) divided by √3 in a star connection.
• Line voltage (Vl) equals phase voltage (Vph) In a delta connection.
• Line current (Il) equals phase current (Iph) in a star connection.
• Line current (Il) is √3 times the phase current (Iph) in a delta connection.
• Three-phase systems use these concepts for efficient power distribution.