The actuation sequence of the brush lifting device is as follows: When the motor is driven by a gear unit which drives a ring which places the three phases in short circuit, only after this operation will all the brushes be raised or spaced apart from the collector . To lower the brushes and to place the rheostat https://www.mrosupply.com/plumbing/rotary-swivel-and-expansion-joints/rotary-joints-and-unions/96929_1115-000-001_deublin/ again in contact with the rotor, the sequence of operation is the reverse of that mentioned above. The operation of a motor with a short-circuited winding rotor is identical to that of a motor with a cage rotor and maintenance is greatly reduced because there is no wear of the brushes.
For this configuration the assembly composed of collector, brushes and brush holders will be sized to withstand the starting conditions. An electric motor which has a motorized brush lifting device can not operate uninterruptedly with the brushes lowered, unless this condition is initially defined prior to construction. It is recommended to use this device when the application requires fewer matches per day, around two matches per day.