- Stator winding faults:
- Turn-to-turn short circuits
- Phase-to-phase short circuits
- Ground faults
- Rotor winding faults:
- Turn-to-turn short circuits
- Phase-to-phase short circuits
- Broken bars
- Mechanical faults:
- Bent shaft
- Misaligned bearings
- Rubbing between stator and rotor
- Excitation system faults:
- Overexcitation
- Underexcitation
Stator winding faults cause an imbalance in the magnetic field produced by the stator, resulting in a non-uniform magnetic field that induces eddy currents in the rotor. These eddy currents generate heat and cause the rotor to become hot.
Rotor winding faults also lead to rotor heating due to increased current flow in the faulty winding. Broken bars can cause the rotor to become unbalanced, leading to vibrations that can further damage the windings and increase heating.
Mechanical faults can cause the rotor to be displaced from its proper position, altering the air gap between the stator and rotor. This variation in the air gap can lead to increased eddy currents in the rotor, resulting in heating.
Excitation system faults can cause the rotor to overheat if the machine is overexcited or underexcited. Overexcitation leads to an increase in the magnetic field strength, inducing higher eddy currents in the rotor. Underexcitation causes the machine to operate at a low power factor leading to an increased current in the rotor windings, which can result in overheating.
To prevent rotor heating, regular inspections and maintenance of the machine are crucial. Prompt identification and rectification of any fault conditions are essential to ensure the machine operates safely and efficiently.
