Statystyka uszkodzeń silników wysokonapięciowych prądu przemiennego w elektrowniach zawodowych

Main devices in electric power station (feed water pumps, coal pulverizers, mill ventilators ect.) are driven by high-power inductive motors 160 - 6300 kW. Analysis of failure frequency ot these motors shows that 50% of failures (Table l) occur in motors which drive feed water pumps and mill ventilators. About 75% of motors' failures occurs in their stators (Table 3). The rest of failures has their proximate source in rotors' squirrel-cage winding and rolling bearing. Statistics shows the mean time to failure of new motor is about 14 years. The mean time from the last failures for rewinded motors is about 10 years (Table 4). In stators usually break down their windings. The main reason of that are short-circuits in coil windings in the stator iron (Fig. 3 and 4) and in end windings coils (Fig. l, 2 and 5 to 7). These short-circuits cause short-circuit currents and in consequence the deformation of coil windings (Fig.8) is caused by the electrodynamic forces. In single squirrel-cage rotors failures usually occur in connection zone of cage bars with ring (Fig. 9 and 10). In double squirrel-cage rotors failures occurring in starting cage are caused by electric arc burning-off of starting cage bars in rotor core grooves (Fig. 11). More frequently electric arc burning-off occurs in starting cage between rotor core and rings (Fig. 12 and 13). Failures of rotors rolling bearings results in stator core seizing by rotor core (Fig 14).