Which of the following is not an example of a slash-rated three-phase system?

The concept of a slash-rated three-phase system involves specifying the voltage and number of phases in a format that indicates the potential configurations of the system. A typical way to represent these systems is to include a voltage designation along with the number of wires, such as "480V three-phase, three-wire."

In the provided options, the designation "480V three-phase, three-wire" is a common configuration for a three-phase system; however, it is not classified as a slash-rated system. In slash-rated systems, the voltage typically represents the line-to-line voltage (like in common slash ratings such as "480/277V"), while the configurations must also reflect a 4-wire connection when appropriate.

The other options represent combinations that fit the criteria for being considered slash-rated three-phase systems since they include both the phase and a number of wires that may represent line-to-line and line-to-neutral configurations appropriately. Thus, the 240V three-phase, four-wire, the 600V three-phase, four-wire, and the 208V three-phase, three-wire options all contain elements that correspond better with a slash-rated classification, making the first option the outlier.