Effects of instantaneous power-supply failure on the operation of slip-energy recovery drives

Performance analyses of slip energy recovery drives during and at recovery after instantaneous power-supply failure in one or more supply phases have been carried out. Transient slip energy recovery drive currents and voltages under such fault conditions have been obtained theoretically using mathematical models which take into account the three-phase, single-phase, and disconnected power-supply conditions. A detailed set of theoretical and experimental results is given to clarify the expected behavior of the drive under instantaneous power-supply failure of a few cycles duration and at recovery. Insertion of an external bypass resistor into the dc link by the use of a static switch has been discussed to suppress the induced overvoltages and, hence, overcurrents in the rotor windings and converters, after recovery of the supply.