In a wye-connected system, how do you relate coil (phase) voltage to system (line) voltage?

In a wye-connected system, how do you relate coil (phase) voltage to system (line) voltage?

• A. System voltage equals Coil voltage
• B. Coil voltage equals System voltage divided by 3
• C. Coil Voltage Multiplied by 1.732 equals System voltage
• D. System voltage divided by 1.732 equals Coil voltage

Answer: (C)

In a wye-connected system, the line (system) voltage is the voltage between two lines, while the coil (phase) voltage is the voltage from a line to neutral. Because the three phase voltages are 120 degrees apart, the line-to-line voltage is the vector difference of two phase voltages and has a magnitude that is √3 times the phase voltage. So the coil voltage times √3 equals the system voltage. In other words, V_line = √3 × V_phase. A common takeaway is that V_line ≈ 1.732 × V_phase (for example, 277 V phase voltage gives about 480 V line voltage in a 480Y/277 V system).

In a wye-connected system, the line (system) voltage is the voltage between two lines, while the coil (phase) voltage is the voltage from a line to neutral. Because the three phase voltages are 120 degrees apart, the line-to-line voltage is the vector difference of two phase voltages and has a magnitude that is √3 times the phase voltage. So the coil voltage times √3 equals the system voltage. In other words, V_line = √3 × V_phase. A common takeaway is that V_line ≈ 1.732 × V_phase (for example, 277 V phase voltage gives about 480 V line voltage in a 480Y/277 V system).