In a three-phase Y connected AC power system, what is the voltage between each pair of hot legs if the voltage from leg to ground is 120 volts?

In a three-phase Y connected AC power system, what is the voltage between each pair of hot legs if the voltage from leg to ground is 120 volts?

• A. 120 volts
• B. 240 volts
• C. 208 volts
• D. 480 volts

Answer: (C)

In a three-phase Y connected AC power system, each leg of the system is typically at a certain voltage level relative to ground, which is often referred to as phase voltage. In this case, if the voltage from each leg to ground is 120 volts, this represents the phase voltage. To determine the line-to-line voltage (the voltage between each pair of hot legs), you can use the relationship between phase voltage and line voltage in a three-phase Y (wye) configuration. The formula for calculating line-to-line voltage (V_LL) in relation to phase voltage (V_Ph) is: V_LL = √3 × V_Ph By substituting the known phase voltage into the formula, we find: V_LL = √3 × 120 volts = 1.732 × 120 volts Calculating that gives approximately 208 volts. This means the voltage between each pair of hot legs in a three-phase Y system, when the voltage from each leg to ground is 120 volts, is indeed about 208 volts. Therefore, this understanding of the relationships between phase and line voltages in a three-phase system clearly leads to the conclusion that 208 volts is the proper answer.

In a three-phase Y connected AC power system, each leg of the system is typically at a certain voltage level relative to ground, which is often referred to as phase voltage. In this case, if the voltage from each leg to ground is 120 volts, this represents the phase voltage.

To determine the line-to-line voltage (the voltage between each pair of hot legs), you can use the relationship between phase voltage and line voltage in a three-phase Y (wye) configuration. The formula for calculating line-to-line voltage (V_LL) in relation to phase voltage (V_Ph) is:

V_LL = √3 × V_Ph

By substituting the known phase voltage into the formula, we find:

V_LL = √3 × 120 volts = 1.732 × 120 volts

Calculating that gives approximately 208 volts. This means the voltage between each pair of hot legs in a three-phase Y system, when the voltage from each leg to ground is 120 volts, is indeed about 208 volts. Therefore, this understanding of the relationships between phase and line voltages in a three-phase system clearly leads to the conclusion that 208 volts is the proper answer.