Correct Answer - Option 1 : Short circuited
Explanation:
The principle of operation of a 3-phase induction motor is most similar to that of the transformer with a shorted secondary. A transformer has primary and secondary windings, primary winding induces a voltage in secondary. In 3 phase induction motor, primary winding induces a voltage in secondary but secondary is shorted.
Induction motor is also known as a generalized transformer. Both the machines are almost similar, but they have following differences.
- Transformer is a device in which two windings are magnetically coupled and when one winding is excited by AC supply of certain frequency, the emf gets induced in the second winding having same frequency as that of supply given to the first winding
- The winding to which supply is given is called primary winding while winding in which emf gets induced is called secondary winding, the induction motor can be regarded as the transformer
- The difference is that the normal transformer is an alternating flux transformer while induction motor is rotating flux transformer
- The normal transformer has no air gap as against this an induction motor has distinct air gap between its stator and rotor
- In an alternating flux transformer, the frequency of induced emf and current in primary and secondary is always same, however, in the induction motor frequency of emf and current on the stator side remains same but frequency of rotor emf and current depends on the slip
- In case of the alternating flux transformer the entire energy present in the secondary circuit, is in the electrical form
- In an induction motor part of its energy in the rotor circuit is in electrical form and the remaining part is converted into mechanical form
