Thursday, May 23

Rotating Magnetic Field

Introduction to Rotating Magnetic Field:

A rotating magnetic field is a kind of magnetic field which ideally changes its direction at an angular rate which is constant. In the working of a motor that works on alternating current, the rotating magnetic field plays a key role as it is associated with its principle of operation. The concept of rotating magnetic field was introduced by Nikola Tesla in 1882. Galileo Ferrari's has done his research independently to introduce some more features of this concept in 1885.

Production of Rotating Magnetic Field

A rotating magnetic field which is symmetric can be produced using as few as three coils. To produce a rotating magnetic field, three coils should be driven by a symmetric three phase a.c. current and one of the phases is shifted to 120 degrees as compared to the other phase. In this case the magnetic filed should be taken as the linear function of the current which is flowing in the coil. The three phases which are 120 degrees out of phase compare to each other when applied to the axis of the alternating current motor then it produces a single rotating vector. This rotating vector follows the magnetic field in the coil and hence produces a rotating magnetic field .

Application of Rotating Magnetic Field

Rotating magnetic fields can also be used in the induction motors because the magnets, which are used, degrades with time and the induction motor use the short circuited rotor instead of a magnet, which is easily follow the rotating magnetic field produced by a stator, which is multi coiled. In the case of the induction motor, the turns of the rotor which is short circuited, develops the eddy current in the rotating magnetic field of the stator which is used to move the rotor by the developed Lorentz force. Such motors are generally not synchronous but they have involved a necessary degree of the slip by which the current will be produced due to the relative motion of the field and the rotor.

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