Direct connection of an induction motor with a DC supply is not possible for its starting, apart from using a transformer to step up voltage and other innovative methods.
Induction motors operate on an AC source of supply only All induction motors are designed for AC supply only.
Here are the key reasons why a DC supply cannot be used:
Operating Principle of an Induction Motor
Induction motors use the principle of electromagnetic induction, which operates under the condition that there is an establishment of a rotating magnetic field.
This rotating magnetic field is developed from the ac supply connected to the stator windings.
A DC supply would develop a static magnetic field which would not generate the required amount of currents in the rotor for the development of torque.
Magnetic Field
If there were DC supply then the field produced in the stator of the motor would be constant and would not be alternating.
This would not generate the right current in the rotor as the one needed to establish torque for rotation.
Rotor Heating
When a DC supply be applied, the motor rotor will most probably overheat because it does not rotate and hence does not get a cooling air flow.
This could lead to physical deterioration of the rotor as well as other parts of motor.
Motor Design
Another type of motor for AC is the induction motor and the motors are designed in such a way that the material used and the windings in the motors are well suited to AC.
They may not function properly with DC; this would result in inefficiency and, at times, destruction of the core as well as the winding arrangements.
In induction motor applications for starting and running, it is essential to have an AC supply for the desired creation of the rotating magnetic field.