The 30A slip ring collectors are sets of rings coupled with brushes designed to allow current to pass from a fixed to a rotating part. The 30A series is used to supply crane motors, cable winders etc. These units are suitable only for transmitting currents with 50/60Hz supply frequency. The 30A slip ring collectors may have only 30A line rings or they may have both 30A line rings and 10A auxiliary rings.
They have an shock-resistant thermoplastic protection to prevent accidental contacts with live parts; the protection has small downward holes to allow air circulation and prevent moisture. The lower support plate is also provided with three holes to drain the moisture which may form inside the unit.