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Saturday 27 July, 1996 | RSS Feed

Structure and characteristics of the brushless motor

by AOMag | post a comment

Within the scope of the three-phase brushless motor permanent magnet synchronous motor, the magnetic field of permanent magnet synchronous motor from the permanent magnet motor rotor. Here, the characteristics of the permanent magnet, to a large extent determine the nature of the motor. Permanent magnet materials currently used mainly ferrite magnets, Alnico magnets, NdFeB, etc. This feature is based on a linear relationship between the magnetic flux density and magnetic field strength of several of the most widely used is neodymium. Its maximum range of linear relationship, known as the third generation of rare earth permanent magnet alloy.

Permanent magnets arranged on the rotor in two ways: one is the forming of a permanent magnet mounted on the rotor surface, the so-called outside-mounted; the other is formed inside the permanent magnets embedded in the rotor, the so-called built-in. Depending on the installation method of permanent magnet, the shape of the permanent magnets can be divided into two sectors and rectangular. Fan rotor magnet structure having an armature inductance is small, the advantages of small cogging torque, but susceptible to the armature reaction. And the magnetic flux can not concentrate, low air gap flux density, electrodes exhibit convex characteristics. Rectangle magnet rotor configuration presents Salient features large electrical inductance, cogging torque, but the magnetic flux can be concentrated to form a high magnetic flux density, it is suitable for large-capacity motor, since the motor exhibits Salient features, you can use magnetic resistance torque, in addition, that the permanent magnet rotor structure, easy to fly, it can be used for high-speed motors.

Different of cloth according to the determined rotor structure corresponding to each phase excitation through potential, three-phase permanent magnet synchronous motor can be divided into two types: sine and square wave-shaped permanent magnet synchronous motors, the former potential distribution of each phase sinusoidal excitation flux waveforms, which each phase is wavy side, depending on the magnetic structure and the permanent magnet shapes and different structure for the radial excitation, permanent magnet direct-uniform air gap if the use of dilute large material, the use of non-uniform air gap or radial structure of the permanent magnet excitation of non-uniform magnetic field in the direction of the length of the air gap magnetic field can achieve sinusoidal waveform. It should be noted rare earth permanent magnet motor square wave belongs to the category of permanent magnet brushless DC motor, and a rare earth permanent magnet motor is generally sinusoidal three-phase AC permanent magnet synchronous servo motors. But this is not absolute, whether it is a three-phase permanent magnet brushless DC motor or three phase permanent magnet AC synchronous motor, mainly on the way the motor control system, depending on the type of the motor rotor position sensor.

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