Consider the following statements regarding three-phase systems:1.Total power = √3 VL IL cosϕ.2.Power is constant in balanced system.3.Neutral current is zero in balanced load.Which of the above statements is/are correct?
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A balanced three-phase system has three equal-magnitude phase quantities displaced by 120°. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case. Key relation: P=√3 V_L I_L cosφ.
Exam focus: Balanced load ⇒ I_R+I_Y+I_B=0. Common trap: Do not apply zero-neutral-current result to unbalanced or harmonic-rich loads.
Formula / Key Relation
P=√3 VL IL cosφ.
Detailed Explanation
Correct Answer: D - 1, 2 and 3 Quick Concept Explanation A balanced three-phase system has three equal-magnitude phase quantities displaced by 120°. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case. Key relation: P=√3 V_L I_L cosφ.Exam focus: Balanced load ⇒ I_R+I_Y+I_B=0. Common trap: Do not apply zero-neutral-current result to unbalanced or harmonic-rich loads. Statement-wise Verification Statement 1 - Correct.Total power = √3 VL IL cosϕ.P=√3 V_L I_L cosφ. Statement 2 - Correct.Power is constant in…
Correct Answer: D - 1, 2 and 3
Quick Concept Explanation
A balanced three-phase system has three equal-magnitude phase quantities displaced by 120°. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case. Key relation: P=√3 V_L I_L cosφ.
Exam focus: Balanced load ⇒ I_R+I_Y+I_B=0. Common trap: Do not apply zero-neutral-current result to unbalanced or harmonic-rich loads.
Statement-wise Verification
Statement 1 - Correct. Total power = √3 VL IL cosϕ. P=√3 V_L I_L cosφ.
Statement 2 - Correct. Power is constant in balanced system. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case.
Statement 3 - Correct. Neutral current is zero in balanced load. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case.
Core Concept
A balanced three-phase system has three equal-magnitude phase quantities displaced by 120°. For a balanced load, the instantaneous total three-phase power is constant and the phasor sum of phase currents is zero, so a neutral conductor carries no current in the ideal balanced case.
Formula / Key Relationship
P=√3 V_L I_L cosφ.
Why the Other Options Are Wrong
Option A is incorrect because it omits correct statement(s) 3. Option B is incorrect because it omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 2.
Exam Shortcut / Approach
Balanced load ⇒ I_R+I_Y+I_B=0.
Common Mistake
Do not apply zero-neutral-current result to unbalanced or harmonic-rich loads.
Quick Revision
Three-Phase Power and Neutral Current is linked with Balanced Three-Phase System, Three-Phase Circuits and Basic Electrical Engineering. Balanced load ⇒ I_R+I_Y+I_B=0.
Quick Trick
Balanced load ⇒ I_R+I_Y+I_B=0.
Why Other Options Are Wrong
Option A is incorrect because it omits correct statement(s) 3. Option B is incorrect because it omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 2.
Common Mistake
Do not apply zero-neutral-current result to unbalanced or harmonic-rich loads.
Exam Tip
Balanced load ⇒ I_R+I_Y+I_B=0.
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