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AC Machines

AC Machines. 6077SA NUE 046. 3 Phase Synchronous Alternators. Alternators. Identify the basic components of a Alternator List the types of rotors used Test motor windings for suitability to connect to the supply Connect in both Clockwise and counter clockwise rotation

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AC Machines

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  1. AC Machines 6077SA NUE 046

  2. 3 PhaseSynchronous Alternators

  3. Alternators Identify the basic components of a Alternator List the types of rotors used Test motor windings for suitability to connect to the supply Connect in both Clockwise and counter clockwise rotation List the steps for dismantling it At the end of this section you will be able to:

  4. Types Governed By: • Load Current Requirements • Single or Three Phase • Prime Mover Speed

  5. Prime Mover Determines Speed of Alternator High Speed Slow Speed • Windmill • Diesel Motor • Water turbine • Steam turbine

  6. Number of Poles Speed Determines Number of Poles 50 Hz Required OR

  7. Number of Poles 375 RPM = 16 Poles 750 RPM = 8 Poles 1500 RPM = 4 Poles 3000 RPM = 2 Poles

  8. Number of Poles Determines Shape of Alternator 16 Poles • Large Diameter • Short length Salient Pole

  9. Number of Poles Determines Shape of Alternator • Small Diameter • Long 2 Poles Cylindrical

  10. Generated Voltage Dependant on • Flux density • Flux strength • Speed of rotation • Number of turns per pole • Length of pole • Area of pole face

  11. Generated Voltage Φm f N = Maximum flux = Frequency = Number of poles

  12. Generated Voltage Φm f N kp kd = Maximum flux = Frequency = Number of poles = Pitch factor =Distribution or Breadth factor

  13. Voltage Regulation • Resistance • Inductance I E V Voltage Drop Due to R Voltage Drop Due to XL Coils have both

  14. Voltage Regulation Vg Unity PF Terminal Voltage Line Current

  15. Voltage Regulation V less than E I V E Lagging PF of 45

  16. Voltage Regulation Vg Unity PF Terminal Voltage Lagging PF Line Current

  17. Voltage Regulation V More than than E I E V Leading PF of 45

  18. Voltage Regulation Leading PF Vg Unity PF Terminal Voltage Lagging PF Line Current

  19. Voltage Regulation 100 x VNo Load – V Full Load R% = VFull Load If PF = Unity 100 x I x (R x cos + XL x sin) R% = VFull Load

  20. Excitation With Brushes DC Generator Brushes Rotor Stator

  21. Excitation Without Brushes Rotating Components Excitation Stator Sensor & Regulator

  22. Synchronising Generators Synchronized when all lamps dark

  23. Synchronising Generators Synchronized when 1 lamp dark 2 lamps light

  24. END

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