3 phase motors 1

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  • The winding of a 3 phase motor are consist of 3 separate windings connected 120 degrees electrically apart
    These winding can be connected either in star or delta configuration
    The windings start of the winding is usually labeled A,B 0r C and ends of the winding are labeled A1,B1,C1 or sometimes the letters U, V ,W are used
    (Draw star delta and label)
  • 3 phase motors 1

    1. 1. 3-phase Motors - 1 Rotating Magnetic Field
    2. 2. 3-phase Motor Stator o (3 Windings, 120 apart) Phase A (Red) Arrows show Magnetic Flux when phase voltage is POSITIVE Phase C (Blue) A 3-phase Supply (3 voltages, 120o apart) Phase B (Black) B C
    3. 3. 3-phase Motor Stator o (3 Windings, 120 apart) Green arrow shows flux direction Three-phase sequence produces resulting ROTATING MAGNETIC FLUX Green dotted lines show resulting magnet flux Each step is shown here at 0.5 seconds (6 seconds per cycle)
    4. 4. 3-phase Motor Stator o (3 Windings, 120 apart) Each step is shown here at 0.2 seconds (2.4 seconds per cycle)
    5. 5. 3-phase Motor Stator o (3 Windings, 120 apart) Each step is shown here at 0.1 seconds (1.2 seconds per cycle)
    6. 6. 3-phase Motor Stator o (3 Windings, 120 apart) This shows continuous 1 second per cycle
    7. 7. 3-phase Motor Stator o (3 Windings, 120 apart) The STATOR core is a stack of thin silicon steel LAMINATIONS
    8. 8. 3-phase Motor Stator o (3 Windings, 120 apart) Windings are coils placed in SLOTS around the STATOR The coils are connected in groups for each of the THREE PHASES
    9. 9. Speed – Frequency - Poles The SPEED of the rotating magnetic field is determined by: Supply FREQUENCY in Hertz (Hz) Number of magnetic POLES produced by the stator windings
    10. 10. Speed – Frequency - Poles The SPEED of the rotating magnetic field is determined by: x2 Poles to PAIRS x60 rps to rpm N Synch Synchronous Speed (rpm) Frequency (Hz) 120 f = P Number of Poles per phase
    11. 11. Production of Torque
    12. 12. Production of Torque Note that the ROTOR LAGS behind the rotating magnetic field (Watch the pink dot)

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