Julissa Green
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Mar 3, 2022
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The basic principle of the permanent magnet motor is to use the phenomenon of electromagnetism and electromagnetic induction to realize the mutual conversion of electric energy and kinetic energy. This article takes the permanent magnet DC motor and the permanent magnet synchronous motor as examples to briefly introduce the permanent magnet motor.
The permanent magnet motor uses permanent magnets to generate the magnetic field of the motor, without the need for excitation coils or excitation current. Compared with traditional electric excitation motors, it has significant advantages such as high efficiency and simple structure. The application range of permanent magnet motors is extremely wide, covering almost all fields of aerospace, national defense, industrial and agricultural production and daily life. With the development of high-performance permanent magnet materials and the rapid development of control technology, the application of permanent magnet motors will become more extensive.
The working principle and structure of a permanent magnet DC motor are similar to those of an ordinary DC motor, except that the permanent magnet poles are used instead of the poles that are excited by the current. Permanent magnet DC motors can be divided into brushed motors and brushless motors according to the different commutation methods. The former is mechanically commutated and the latter is electronically commutated.
The rotor of the permanent magnet brushed DC motor is composed of a rotor iron core, a rotor winding, a commutator, and a rotating shaft, which is the same as the rotor of an ordinary DC motor. To form a permanent magnet DC motor, simply insert the rotor and brush assembly into the stator.
Small and medium power permanent magnet DC motors are widely used in electric bicycles, electric motorcycles and scooters.
In recent years, permanent magnet synchronous motors have developed rapidly. It is characterized by high power factor and high efficiency, and has gradually replaced the commonly used AC asynchronous motor in many occasions. Among them, the asynchronous start permanent magnet synchronous motor has superior performance and is a promising energy-saving motor. The stator structure of the permanent magnet synchronous motor is the same as the working principle of the AC asynchronous motor. The difference from the ordinary asynchronous motor lies in the rotor structure. The permanent magnet poles are installed on the rotor, and the permanent magnets are arranged in various positions in the rotor.
The world’s first motor that appeared in the 1820s was a permanent magnet motor with an excitation magnetic field generated by a permanent magnet. However, the permanent magnet material used at that time was natural magnetite (Fe3O4), and the magnetic energy density was very low. The motor made from it was bulky and was soon replaced by electric excitation motors.
With the rapid development of various motors and the invention of current magnetizers, people have conducted in-depth research on the mechanism, composition and manufacturing technology of permanent magnet materials, and have successively discovered carbon steel, tungsten steel, cobalt steel and other permanent magnet materials. In particular, the AlNiCo permanent magnets appeared in the 1930s and the ferrite permanent magnets appeared in the 1950s have greatly improved the magnetic properties, and various micro and small motors have used permanent magnets for excitation. In the 1960s and 1980s, samarium cobalt permanent magnets and neodymium iron boron permanent magnet materials came out one after another. Their excellent magnetic properties of high remanence density, high coercivity, high magnetic energy product and linear demagnetization curve are particularly suitable for motors, so the development of permanent magnet motors has entered a new historical period.
For more information, please visit https://www.stanfordmagnets.com/.
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