The circuit demonstrates how two 277 Volts sources produce 480 Volts. The green and orange sine waves represent 277 Volts RMS which peaks at 392 Volts which produce the difference blue sine wave of 480 Volts RMS which peaks at 678 Volts. If you were to touch one of the wires and get shocked it's 277 Volts with respect to ground. I have heard people say they felt 480 but it was really 277.
