You almost have to go the route of Slip Rings to get power up onto the movable / rotating part of the mechanism. You can minimize the number of slip rings be sending the data back over the +Vcc line. Steve's mention of using a slip ring set for a thermocouple connection probably does not demand any intellegence mounted on the movable part, just the sensor. Your mention of a data rate of 3K bits/second seems to imply that there is some intellegent device on the moving mechanism that would require power.

There is a scheme to get power across a barrier without a set of slip rings. I have done this by putting two torroid in parallel at the axis of the rotation point. The stationary one is excited with an AC signal which then couples into the second coil on the movable part where it is then rectified into usable DC power.

Michael Karas