What would the current curve of the stator of a slip ring induction motor look like if the resistive load of the rotor suddenly rose towards infinity?
I imagine it would behave like the primary current of a transformer with no load on the secondary and drop to a low level.
I have a weird problem with a slip ring induction motor turning a 100 ton converter. The thermal overload is set to 100A and sometimes the motor behaves normally and rotates the converter drawing around 60A on each phase. Increasingly often, in fact about 99% of the time now, the converter turns very slowly and sometimes even stops completely. The stator current shoots up to 160A per phase and the thermal overload trips. A mechanical overload in the converter or gearbox seems unlikely as the gearbox is also driven by a separate low speed induction motor on a separate axle and this behaves normally, drawing
25A on each phase when rotating the converter.I think a bearing fault on the main motor is most likely, but I am also interested in the possible effects of a fault in the external resistive load on the rotor, which consists of four resistors shorted sequentionally by contactors as the converter gathers momentum.
Of course the best solution would be to rip out this ancient crap and replace it with an inverter driven induction motor.
Svenne