Rotary Transfomers

-----------------
How do you expect a transformer and a slip ring to perform the same function? What is it exactly that you want to do? Define your problem somewhat more clearly.

Easily. There are three main methods for coupling electrical signals to rotating parts: slip rings, rotary capacitors, and rotary transformers. The main problem with slip rings is the electrical noise they generate; also, at high speed, it is difficult to maintain reliable electrical conductivity between the slip ring and the brush. Rotary capacitors are better with respect to noise but more difficult to make.
Rotary transformers in VCRs are constructed by winding the primary and secondary windings into separate halves of a ferrite cup core; these concentric halves face each other, with each half mounted to one of the rotating parts.
Rotary transformers can be found in various kinds of equipment including VCR head drums, rotary ultrasonic testers used in metal tube manufacture, and torque sensors installed on electric motors.

Thank you. I hadn't thought of that.