Welcome to Study Room SA
0 votes
in Grade 12 by Master (947k points)
recategorized by | 1.5k views

1 Answer

0 votes
Best answer

The operation of three-phase squirrel cage induction motor.

  • Three-phase supply is such that the peak voltage of each phase is reached at 120o intervals.
  • When a squirrel cage motor is connected across a three phase alternating supply, alternating current will flow in the respective stator windings.
  • As a result the alternating current will set up a magnetic field in and around the respective stator windings.
  • The stator windings are however spaced 120o apart around the axis of the motor.
  • The result is that the magnetic field has a rotating maximum flux density as the peak in each winding is reached at a 120o interval, resulting in a rotating magnetic field.
  • A squirrel cage rotor consists of cage like conductors bound electrically with a short circuit ring at each end.
  • The rotating magnetic field will sweep across the rotor conductors of the squirrel cage rotor.
  • As the magnetic field sweeps over the rotor conductors, the magnetic flux will cut/cross the rotor conductors.
  • Faraday's law determines that an EMF will be induced in the rotor windings due to the sweeping action of the rotating magnetic field.
  • Lenz's Law will determine that the induced current will be such that its force will oppose the inducing action (from the stator), thus establishing a repelling force between the stator and rotor (due to the opposing magnetic fields), thus forcing the rotor into rotation.
  • When the speed of the rotor approaches the speed of the rotating magnetic field (synchronic speed), the inducing action is reduced and the rotor tends to slow down. The result is that the rotor rotates at a speed lower than that of the rotating magnetic field (synchronic speed)
by Master (947k points)
selected by
No registration is required in order to post/ask, comment and or answer any question on this forum. Please note this website was created to help learners discuss their school work with other learners and teacher from anywhere around South Africa for free. Why Free? We generate our revenue through adverts to keep the forum running 24/7
Welcome to Study Room, where you can ask questions and receive answers from other members of the community. Members/Users are also allowed to answer any questions or add comments. If you think a certain answer is wrong or slightly incorrect' please use the comment button below the answer to add your suggestion.

Let's see how smart you are Click/Touch Here To help other students on their questions

1,840 questions
594 answers
1,166,574 users
Help get things started! Simple pick and answer 1 or more questions to help those who are in need of your help. This site was mainly created for grade 10 - 12 pupils to exchange questions and answers. I' the admin of the site do try answering some of the questions but just because of the heavy load of work I have to attend on the site as a sole admin.