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The rated voltage of a 3 phase power system is given by
RMS peak voltage
Peak phase voltage
RMS line to line voltage
Peak line to line voltage
RMS line to line voltage
In 3-phase power systems, the rated voltage is standardly defined as the RMS value of the line-to-line (phase-to-phase) voltage. This convention ensures uniformity in equipment insulation ratings and power distribution standards worldwide.
In 3-phase power systems, the rated voltage is standardly defined as the RMS value of the line-to-line (phase-to-phase) voltage. This convention ensures uniformity in equipment insulation ratings and power distribution standards worldwide.
VLтАЛ=3тАЛVphтАЛ тАФ Relationship between line and phase voltage in a star connection
VrmsтАЛ=2тАЛVpeakтАЛтАЛ тАФ Conversion from peak to RMS for sinusoidal AC signals
A balanced 3-phase system has three conductors carrying voltages with a 120┬░ phase displacement. The line-to-line voltage (VLтАЛ) is related to the phase voltage (VphтАЛ) by the factor 3тАЛ in star-connected systems. By specifying the line-to-line RMS value, engineers can determine the insulation requirements and power capacity independent of the specific load connection type (Star or Delta).
RMS value is used because it corresponds to the equivalent DC heating effect.
Line-to-line voltage is the potential difference between any two of the three supply lines.
Standard industrial ratings (e.g., 415V, 11kV) always refer to the RMS Line-to-Line voltage.
Standardization of insulation levels across equipment.
Provides a consistent metric for power calculation regardless of star/delta connection.
RMS representation accounts for the effective energy transfer.
Electrical grid voltage ratings
Transformer winding specifications
Motor terminal voltage ratings
Option A is incorrect because peak voltage is used for insulation breakdown testing, not as the system rating.
Option B refers to the phase voltage, which is only 1/3тАЛ of the rated line voltage in a Star (Wye) system.
In India, the standard low-tension 3-phase rated voltage is 415V RMS Line-to-Line.
C is correct тАФ The rated voltage of a 3-phase power system is defined as the RMS line-to-line voltage.
Remember that in power systems, all standard references to 'system voltage' are always RMS line-to-line unless explicitly stated otherwise (e.g., in transient analysis).