What are the line-to-line voltages when a 3Ø, 4-W supply system delivers 120/240 volts?

In a 3-phase, 4-wire system, the line-to-line voltage is typically the voltage measured between any two of the three phases. When dealing with a system that delivers 120/240 volts, the 120 volts represents the line-to-neutral voltage, while the 240 volts represents the line-to-line voltage.

To understand this, remember that in a three-phase system, the line-to-line voltage is calculated using the following relationship:

[ V_{LL} = \sqrt{3} \times V_{LN} ]

where ( V_{LL} ) is the line-to-line voltage and ( V_{LN} ) is the line-to-neutral voltage. In this context, since the system is defined to provide either 120V (line-to-neutral) or 240V (line-to-line), it confirms that you have a system configured to use 240 volts as the line-to-line voltage.

Therefore, when you consider the 120/240 volts specification of the supply system, it directly indicates that 240 volts is the line-to-line voltage. This is why the correct choice is 240 volts.