Slip rings are normally copper bands, molded onto an insulating material, then pressed on the steel shaft of the rotor.
Each end of the rotor winding is connected to one of the copper bands, so that as the rotor rotates, the brushes can make a connection with each end of the winding.
The brushes are made of a combination of copper and carbon, and are carried in brush holders mounted in the end frame.
Slip Ring
A slip ring (in electrical engineering terms) is a method of making an electrical connection through a rotating assembly. Slip rings are commonly found in electrical generators for AC systems and alternators.
A slip ring consists of a conductive circle or band mounted on a shaft and insulated from it. Electrical connections from the rotating part of the system (such as the rotor of a generator) are made to the ring. Fixed contacts or brushes run in contact with the ring, transferring electrical power or signals to the exterior, non-rotating part of the system.
Brushes
This system is similar to the brushes and commutator found in many types of DC motors. Slip rings can also be used where electrical power or signals need to be transferred to a rotating device, such as a rotating visible light beacon. (In high speed or low friction environments, rotary transformers are often used instead of slip rings.)
In electrical engineering, brushes conduct current between stationary wires and moving parts, most commonly in a rotating shaft. Most importantly, in an electric motor, an alternator or electric generator, the coils of the rotor have to be connected. To accomplish this, two metal (copper or brass) 'slip rings' are affixed on the shaft and springs press braided copper wire 'brushes' onto the rings which conduct the current. Later, these copper wire brushes were replaced with carbon blocks — but these blocks are still called brushes. As the brushes are slowly abraded they might have to be replaced, provided this is possible at all.
If the copper rings are split in parts with "interlaced" connections, the arrangement is called a commutator.
Source: CDX Global & Wikipedia - en.wikipedia.org
