Permanent Magnet Materials in Coreless Motors

With the continuous development of science and technology, motor technology is also constantly innovating. Especially in today’s industrial field, higher expectations and requirements are constantly put forward for the servo characteristics of motors, and coreless motors have emerged as the times require.

Coreless motors are DC permanent magnet servo and control motors, and can also be classified as micro motors. The hollow cup motor has outstanding energy-saving characteristics, sensitive and convenient control characteristics and stable operation characteristics, and its technological advancement is very obvious. As a high-efficiency energy conversion device, it represents the development direction of electric motors in many fields.

Structure and principle of coreless motor

The following figure is a simplified structural diagram of a general coreless motor. The coreless motor is a DC permanent magnet motor. The main difference from ordinary brushed and brushless DC motors is the use of an ironless rotor, also known as a coreless rotor.

The rotor is directly wound with wires, without any other structure to support these windings, and the winding itself is made into a cup shape, which constitutes the structure of the rotor (as shown in the figure below). Due to the structural change of the rotor, the operating characteristics of the motor have been greatly improved. It not only has outstanding energy-saving characteristics, but more importantly, it has control and drag characteristics that iron core motors cannot achieve.

Coreless motors are divided into two types: brushed and brushless. The rotor of the brushed coreless motor has no iron core, and the stator of the brushless coreless motor has no iron core. Common coreless motor models in the market have diameters of Φ4, Φ6, Φ7, Φ8, Φ10, Φ12, Φ15 and so on.

Permanent Magnet Materials in Coreless Motors

Permanent Magnet Materials in Coreless Motors

Advantages and Applications of Coreless Motors

Coreless motor has a series of advantages such as high power density, high efficiency, no torque lag, no cogging effect, low starting torque, no radial force between rotor and stator, smooth speed curve, low noise, and good heat dissipation effect. .

The application of hollow cup motors has developed rapidly for more than ten years after entering the large industrial and civil fields from the military and high-tech fields, especially in industrially developed countries, and has involved most industries and many products.

Follow-up systems that require fast response. Such as the rapid adjustment of the flight direction of the missile, the follow-up control of the high-magnification optical drive, the fast automatic focus, the highly sensitive recording and testing equipment, the industrial robot, the bionic prosthesis, etc., the hollow cup motor can well meet its technical requirements.
Products that require a smooth and long-lasting drag on the drive element. Such as all kinds of portable instruments and meters, personal portable equipment, field operation equipment, electric vehicles, etc., with the same set of power supply, the power supply time can be extended by more than double.

All kinds of aircraft, including aviation, aerospace, model aircraft, etc. Utilizing the advantages of light weight, small size and low energy consumption of the hollow cup motor, the weight of the aircraft can be reduced to the greatest extent.
All kinds of household electrical appliances and industrial products. Using the hollow cup motor as the actuator can improve the product grade and provide superior performance.

Because the hollow cup motor is small in size, many products with relatively small volume requirements use hollow cups as power components. For example; toys and gifts (toy cars, model airplanes, etc.), beauty and massage products (face brushes, importers, facial massagers, etc.), daily necessities (electric toothbrushes, shampoo brushes, hair straighteners, etc.). Permanent Magnet Materials in Coreless Motors

Coreless motor magnet

Sintered NdFeB permanent magnets are generally used in coreless motors, which have the characteristics of high remanence, high coercive force, and high magnetic energy product, and are the permanent magnet materials that best meet the requirements of coreless motors on the market. Under the same size motor and winding data, the performance of the magnetic steel directly affects the speed of the motor. Common NdFeB magnets suitable for coreless motors are ring-shaped, with properties such as N40, N45, etc., and the temperature resistance is about 100 °C.

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