23/02/23 05:23:37
@lecture @IS
Presentation
- A turbo generator (generators used in steam/gas turbines) is a synchronous generator.
- In an induction motor the rotating magnetic field is generated by phase shifited voltages. In a synchronous generated the field is ‘manually’ rotated with heat generated to turn the turbine and then rotor.
- The generator is run with negative slip, that is, unlike the induction motor we’ve look at the rotor is ahead of the rotating magnetic field of the stator windings.
- The equivalent circuit for the synchronous generator shows the main impedances we have to think about. Mainly, there is heating of the rotor field and the armature windings, then reactances are added due to the start windings.
- The field generated in the air gap is a combination of that created by the field winding which induces current in the stator and the ‘reaction’ voltage by the stator on the field winding.
- R_a is the effective resistance includes the effects of the operating temperature and the skin effect caused by the alternating current flowing through the armature winding.
- The synchronous reactance X_s takes into account all the flux, magnetizing as well as leakage, produced by the armature (stator) current
- The synchronous generator is considered to give a lagging current. It’s phasor equation is
- .
- The terminal voltage is led by that of excitation in the rotor.
- What happens if so much torque is created to change what the rotor is locked into?
- Exam: 80% CA: 20%.