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AC Machines

AC Machines. 6077 SA NUE 046. 1 Phase Induction Motors. Identify the basic components of a 1Ø induction motor 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 6077 SA NUE 046

  2. 1 Phase Induction Motors • Identify the basic components of a 1Ø induction motor • 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:

  3. Types Squirrel Cage • Split phase • Capacitor start • Capacitor start Capacitor run • Permanent split phase capacitor run • Shaded Pole Wound Rotor • Series universal • Repulsion

  4. Construction

  5. Construction Run or Main Windings • Low resistance • High XL • Set deeper in laminations to increase XL Start or Auxiliary Windings • High resistance (thinner wire) • Low XL (fewer turns) • Set shallower in laminations to limit XL

  6. Electrical Characteristics IRef IS Run Winding Large phase Angle due to high Inductance IR Start Winding Phase Angle less, as Inductance is less than run winding

  7. Split Phase Motor Construction Switch opens ≈ 70 – 80% full load speed Low resistance High XL High resistance Low XL

  8. Split Phase Motor Construction Low resistance High resistance

  9. Split Phase Motor Capacitor Start Motor Construction

  10. Electrical Characteristics Capacitor Start Torque = K IR IS sinα K = constant α = Angle between IR and IS IRef IS Split Phase IR

  11. Construction

  12. Construction

  13. Shaded Pole

  14. Shaded Pole

  15. Shaded Pole

  16. Shaded Pole

  17. Shaded Pole

  18. Reluctance Motor 1Φ Synchronous Machine • Low efficiency • Low torque • Constant Speed • Fractional sizes

  19. Reluctance Motor Stator Same as: Split phase or Capacitor Start Motor

  20. Reluctance Motor Rotor Same as: Squirrel cage motor BUT, with Uneven slots cut into laminations to form Salient poles Uneven slots assist in starting Rotor Slots generally ≠ Stator Slots

  21. Reluctance Motor Starting • As per induction motor with squirrel cage providing torque • Centrifugal switch operating as per normal(75%) • As motor is lightly loaded slip speed is small • Rotor salient poles become magnetised and lock with RMF Motor becomes Synchronous

  22. Reluctance Motor If rotor poles are a multiple of the stator poles Motor will operate at sub-multiples of synchronous speed

  23. Hysteresis Motor Rotor • Outer section made up of hardened steel

  24. Hysteresis Motor Rotor • Outer section made up of hardened steel • This outer section supported on the shaft by a NON-MAGNETIC “Arbour”

  25. Hysteresis Motor • Rotor has a very high Hysteresis loss • The rotor tends to become magnetised • A synchronous motor is born PROBLEM Synchronous motors have ZERO START TOURQUE! A Shaded pole stator is used

  26. Universal Motor Not the same as a series DC Motor Fields are laminated for AC current

  27. Universal Motor

  28. Universal Motor

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