1. Contents Introduction Principles of Constructions Sailent pole and Cylindrical pole rotors Field Excitation Systems Stator windings Generation of EMF ELEC3565 Alternator/Synchronous Generator Unit 3

2. Alternators are the principle sources of electrical energy throughout the world, and range in size from a fraction of a kVA to a thousand of MVA. They convert the mechanical driving energy to electrical energy which is then supplied to the electric network. The prime movers of Alternators are Steam turbines (High-speed) Hydraulic turbines (Low-speed) Diesel-engines Gas-turbines Wind turbines The Alternator/Synchronous Generator

3. Structure of A Simple Power Network G1G2G3 G4 G5 Load A cluster of generators Low voltage distribution network with Renewable sourced generators Load High voltage transmission line VoltageStep-up transformer Voltage step-down transformer G6 Circuit breaker 11kV 220kV 11kV load generators 420V 220kV

4. Steam turbine driven alternator

5. The Alternator Flux Cutting Machine Principle A rotating magnet will induce voltage in a stationary coil by flux cutting or rate of change of flux linkage.

6. The Rotor Structure There are two basic forms of rotor construction. (a) salient pole rotor (b) non-salient or cylindrical pole rotor

7. Rotor Constructions Non-salient-pole rotor: usually two- and four-pole rotors. Salient-pole rotor: four and more poles Rotor cores are constructed by thin highly permeable steel laminations to reduce eddy current..

8. 1.Most hydraulic turbines have to turn at low speeds (between 50 and 300 r/min) 2.A large number of poles are required on the rotor Hydrogenerator  Hydro (water)  D  10 m  Non- uniform air-gap NN SS SS NN  d-axis  q- axis Turbine Salient-Pole Synchronous Generator

9. L » 10 m D » 1 m Turbine Blades Steam Stator Uniform air-gap Stator winding Rotor Rotor winding N S  High speed  3600 r/min Þ 2-pole  1500 r/min Þ 4-pole î Direct-conductor cooling (using hydrogen or water as coolant) î Rating up to 2000 MVA Turbogenerator d- axis q- axis Cylindrical Pole Rotor