Just a comment on NON lockup tc's; if the torque converter is not slipping, it is transmitting ZERO power. In other words, if it speeds up to begin transmitting and then converting torque, and the speed differential between stator and impeller becomes zero (stator and impeller are spinning at same speed), no fluid movement occurs and torque transmission ceases.
At this 1:1 speed point, the system loses energy, and torque transmission/conversion resumes when either stator or impeller changes it's relative speed.