Introduction
The magical device that transforms electrical energy into mechanical rotation is the induction motor using “three-phase AC,” commonly known as a three-phase motor. This article will explain in detail the principles behind the “rotating magnetic field” at its core, including the arrangement of stator and rotor, coil placement, and the generation of the magnetic field.
Section 1: Basics of Electricity and Electromagnetic Laws
Electricity and magnetism are two fundamental forces of the universe. When an electric current flows through a conductor, a magnetic field is generated perpendicular to the direction of the current. This phenomenon is known as “Ampere’s right-hand rule,” which illustrates the consistent relationship between the current and the distribution of magnetic field lines.
Section 2: Structure of Three-Phase Motors and Formation of Magnetic Fields
In a three-phase motor, the coils are arranged at an angle of 120 degrees. This special arrangement allows three-phase AC to flow through the coils, causing three currents to change with different phases. The result is a rotating magnetic field, or “alternating magnetic field,” which is synthesized. This synthesized magnetic field becomes the fundamental driving force of the motor.
Section 3: Visualization and Interpretation of Magnetic Fields
As shown in the diagram below, the magnetic field is generated by passing through the coils, and its direction is determined by the current flowing through the coils. Let’s take a closer look at the generation of this magnetic field, the flow of magnetic lines of force, and how they are distributed within the motor.
Section 4: Basics of Three-Phase AC and Phase Relationships
The current supplied from an AC power source changes in the form of a “sine wave.” In a three-phase motor, there are three sine waves, each with a phase difference of 120 degrees. The changes in current created by these three sine waves, which are also spatially shifted by 120 degrees, generate magnetic fields. This spatial and temporal shift in the magnetic fields is the fundamental principle that forms the rotating magnetic field.
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