Device for automatically replacing carbon brush

A device for automatically replacing carbon brushes comprises a plurality of brush boxes installed on a brush frame, a plurality of carbon brushes are arranged in the brush boxes, one carbon brush on each brush box makes contact with a collecting ring of a water turbine generator set to conduct electricity in a friction mode, the other carbon brushes are pressed and fixed in the brush boxes for standby application, and the carbon brushes are fixed to carbon brush clamps. The carbon brush clamp and one end of the rebounding device are fixedly connected into a whole through a spring, the other end of the rebounding device is fixed to the switching shaft in a screwed mode through a bolt, the switching shaft is sleeved with the main shaft, the main shaft is fixed to the middle in the brush box, and the top of the main shaft is in screwed connection with an end cover which blocks the rebounding device in the axial direction of the main shaft. A positioning device is arranged below the middle part of the rebounding