Slip ring

A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure.

It can improve mechanical performance, simplify system operation and eliminate damage-prone wires dangling from movable joints.

They can be used on any rotating object to transfer power, control circuits, or analog or digital signals including data such as those found on aerodrome beacons, rotating tanks, power shovels, radio telescopes, telemetry systems, heliostats or ferris wheels.

Slip rings do the same for electrical power and signal that rotary unions do for fluid media.

With the advent of the Industrial Revolution and the increasing demand for electrical power, the technology behind slip rings started to evolve.

Instead, they transfer both power and data wirelessly via a magnetic field, which is created by the coils that are placed in the rotating receiver, and the stationary transmitter.

[10] Wireless slip rings are considered an upgrade from — or alternative to — traditional slip rings, as their lack of standard mechanical rotating parts means they are typically more resilient in harsh operating environments and require less maintenance.

Sketch of a cross-section of slip rings for an electric motor. In this example, the slip rings have a brush-lifting device and a sliding contact bar, allowing the slip-rings to be short-circuited when no longer required. This can be used in starting a slip-ring induction motor, for example.
Slip rings on a hydroelectric generator;
A - stationary spring-loaded graphite brushes,
B - rotating steel contact ring,
C - insulated connections to generator field winding,
D - top end of generator shaft.
The two most common types of slip ring