When the induction motor is in a stopped state, from the electromagnetic point of view to see, like a transformer, received power to the stator winding is equivalent to the primary coil of the transformer into a closed circuit of the rotor winding is equivalent to the secondary coil of the transformer is short-circuited; stator windingand no electrical contact between the rotor winding, the only contact of the magnetic flux through the stator, air gap, the rotor core into a closed circuit. When the closing moments of the rotor is not turned up, due to inertia rotating magnetic field with maximum cutting speed - synchronous speed cutting rotor windings, the rotor winding inductive the highest possible potential, thus the rotor conductor flowing the current that generate offset of the stator magnetic field of the magnetic energy, as the transformer secondary magnetic flux to offset a flux.

    The stator in order to maintain the original flux when the supply voltage to adapt, then automatically increase the current. Because the rotor current, stator current is increased very large, even up to the rated current of 4 to 7 times, this is the start current reason.

    Why small start current: As the motor speed is increased, the cutting speed of the rotor conductor of the stator magnetic field is reduced to reduce the electric potential induced in the rotor conductors, the current in the rotor conductor is also reduced, so the stator current is used to offset the rotor currents arising the flux that part of the current is also reduced, so the stator current Sorted until normal.