Control induction motor pdf thesis vector

  • Pole amplitude modulation method (PAM) – In this method of speed control of three phase induction motor the original sinusoidal mmf wave is modulated by another sinusoidal mmf wave having different number of poles.
  • Let f 1 (θ) be the original mmf wave of induction motor whose speed is to be controlled.
    f 2 (θ) be the modulation mmf wave.
    P 1 be the number of poles of induction motor whose speed is to be controlled.
    P 2 be the number of poles of modulation wave.
    After modulation resultant mmf wave So we get, resultant mmf wave Therefore the resultant mmf wave will have two different number of poles Therefore by changing the number of poles we can easily change the speed of three phase induction motor.
  • Adding rheostat in the stator circuit - In this method of speed control of three phase induction motor rheostat is added in the stator circuit due to this voltage gets dropped .In case of three phase induction motor torque produced is given by T ∝ sV 2 2 . If we decrease supply voltage torque will also decrease. But for supplying the same load, the torque must remains the same and it is only possible if we increase the slip and if the slip increase motor will run reduced speed.
  • Speed Control from Rotor Side
    1. Adding external resistance on rotor side - In this method of speed control of three phase induction motor external resistance are added on rotor side. The equation of torque for three phase induction motor is The three phase induction motor operates in low slip region. In low slip region term (sX) 2 becomes very very small as compared to R 2 . So, it can be neglected. and also E 2 is constant. So the equation of torque after simplification becomes,

      The  AC Induction motor  is comprised of a simple cage-like rotor and a stator containing three windings. The changing field produced by the  AC line current in the stator induces a current  in the rotor which interacts with the field and causes the rotor to rotate. No brushes are necessary in this design. The base speed of the AC motor is determined by the number of poles built into the stator windings and the frequency of the  AC input voltage . Variable speed control of an AC motor can be accomplished by increasing or decreasing the input frequency.

      Control induction motor pdf thesis vector

      control induction motor pdf thesis vector

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