Do You Know Anything About the Coreless DC Motor?

Coreless electric motor refers to a type of motor, characterized by a large hollow part, usually a hollow cylinder or hollow sphere, and its rotor and stator are placed in the hollow part. Therefore, the motors have a high power density and efficiency. The structure breaks through the traditional rotor structure form, making it easier to produce aerodynamic force when rotating, and can reduce the volume and weight of the motor while maintaining the same output power, so as to achieve more efficient and energy-saving operation. Using the structure of the unintentional rotor, the rotation of the component is very stable, and can achieve fast and accurate dynamic reaction.

This motor is a special electric motor, its structure is different from the ordinary electric motor, so it has many unique characteristics. The main structure is a coreless structure, with an internal drive motor and reducer, and the external is equipped with an output shaft and positioning device. The whole equipment has the advantages of simple structure, small volume, light weight and high efficiency.

The motor is mainly connected by wire harness to the controller, upper shell, bearing, Hall, coil, permanent magnet rotor, housing, bearing and lower shell. The stator is composed of a permanent magnet, a shell, and a flange. The housing provides a constant magnetic field, leaving the motor free of iron loss. There were no soft-magnetic teeth left unavailable. The resulting torque is uniform to smooth operation even at low speeds. At higher speeds, the motor reduces vibration and noise. The copper wire material is made of self-adhesive enameled wire (the coil can be bonded after heating or solvent treatment), and there is no winding core. This structure reduces the eddy current loss, so the efficiency can reach 80% -90%, while the efficiency of the conventional brushless motor is only about 60%. Hollow means a core rotor without a traditional motor in the middle, and the coil looks like a cup. The biggest characteristic of the coreless motor is this cup-like coil, which has no other support structure and is completely made of wire winding. The coil is connected through the connecting plate, and the commutator, and the spindle is linked together. Together, they form the rotor. Generally, this connecting plate is composed of plastic and epoxy resin. It acts as fixed wires and transfer moments. The coil rotates in the gap between the magnet and the shell, thereby rotating the whole rotor. This structure completely eliminates the power loss caused by the formation of eddy current of the core. Due to the large reduction of the rotor weight, the rotational inertia is reduced. Compared with the traditional core motor, the performance of large torque rapid acceleration and rapid deceleration is outstanding.

Coreless micro dc motor is divided into brush and brushless two kinds, brushed coreless motor rotor without core, brushless coreless motor stator without core.

The brushless coreless DC motor adopts electronic redirection, the coil is motionless, and the magnetic pole rotates. Brushless coreless DC motor, is the use of a set of electronic equipment, through the Hall element, sensing the position of the permanent magnet magnetic pole, according to this perception, the use of electronic lines, timely switch the direction of the current in the coil, to ensure the generation of the right direction of magnetic force, to drive the motor. Because it is self-controlled operation, it will not add another start winding on the rotor like the synchronous motor under variable frequency speed regulation, and will not produce oscillation and loss of step when the load mutation, eliminating the disadvantage of hollow glass DC brush micromotor. coreless DC brush micro motor adopts mechanical reversing, magnetic pole motionless and coil rotation. When the motor is working, the coil and the commutator rotate, and the magnetic steel and the carbon brush do not turn. The alternating change of the coil current direction is completed by the commutator and the brush with the rotation of the motor. In the process of rotation will friction the carbon brush, resulting in loss, the carbon brush need to be replaced regularly. Open and break between the carbon brush and coil connector alternate, electric spark will occur, produce electromagnetic break, interference with electronic equipment. coreless motors have the advantages of highly integration and precision machining. Compared with the traditional DC motor, a new integrated structure is adopted, which makes the motor smaller, lighter weight and greater power. At the same time, the precision processing process also makes its smooth operation and less noise, which greatly improves the service life of the motor. Secondly, it is characterized by high efficiency, high torque and high precision. In the case of high rotation speed, it can still maintain a high torque output, and can effectively cope with various load requirements in the working environment. Moreover, due to its high accuracy, it can accurately output the required torque and speed, which can be used in a variety of precision control occasions. In addition, it also has the advantages of low power consumption, low heat value and low vibration. Through the optimization design, the energy loss is greatly reduced, and the heat dissipation is more effective, so as to prevent the motor overheating and ensure the long-term stable operation. Moreover, due to the small vibration and noise generated during operation, it will not cause adverse effects on the working environment and personnel, and will help to improve the work efficiency and the safety of the production environment.

Advantages of a hollow-cup motor

1. The start torque is low No hysteresis loss, no tooth groove effect, the starting torque is very low. At startup, usually the bearing load is the only hindrance. This way can make the wind generator start wind speed is very low.

2. No radial force between rotor and stator The rotor is based on permanent magnets, which have high magnetic energy density and stability, and can provide a relatively strong magnetic field. At the same time, the coil on the stator can also produce a strong magnetic field. Since the rotor and the stator are placed in parallel at a certain distance, there is no direct magnetic interaction between them, so that there is no obvious radial force. The shape of the rotor is a saddle, and the advantage of this structure is that the air gap between the rotor and the stator is balanced. This means that when the rotor rotates, there is no obvious eccentricity, and the distance between the rotor and the stator does not change due to rotation, which further reduces the possibility of radial force.

3. Smooth speed curve with low noise Magnetic levitation technology is used to make the rotation more stable. Can reduce the mechanical friction and vibration, thereby reducing the noise. Secondly, the use of digital control technology, you can more accurately control the speed and Angle. Digital control technology can avoid too large or too small speed changes during rotation, thus ensuring the smoothness of the speed curve. There is no slot of silicon steel sheet, reducing the harmonic of torque and voltage. At the same time, because there is no AC field in the motor, so there is no noise generated by the AC. Only noise from bearings and airflow and non-sinusoidal wave currents.

4. High-speed brushless coil It is necessary to operate at high speed. The low inductance value makes the start voltage low. By increasing the number of poles and reducing the thickness of the casing, the smaller inductance value helps to reduce the weight of the motor. At the same time, the power density is increased.

5. A quick response with a brush coil Copper plate coil mode has a brush motor, due to the low induction value, the current response to the voltage fluctuation is fast. The rotor has little moment of inertia, and the torque is comparable to the current response speed. Thus, the rotor acceleration is 2 times that of the conventional motor.

6. A high peak torque The cup structure is adopted to move the center of gravity down, reduce the rotational inertia of the rotor, and enhance the response speed and control accuracy of the motor. At the same time, the stator also has a unique design to make the magnetic field distribution more uniform, thus improving the output power and torque density, as well as improving the efficiency. Secondly, the lightweight design is adopted to make the rotation inertia small. This means that it requires less energy to perform high-speed rotation tasks, thus reducing power consumption, extending life, and improving its working stability. The voltage harmonic of the motor is low due to the precise position of the coil, and the structure of the copper plate coil in the air smooth. The sine wave drive and the controller enables the motor to produce a smooth torque. This feature is particularly useful in slow-moving objects (e. g., microscopes, optical scanners and robots) and precise position control, which is key.

7. Good heat dissipation effect The bottom of the cup is designed to dissipate heat on the outside, reducing the impact on the internal cup body. Compared with the solid cup formation, the internal motor is more likely to heat, and the solid cup body can not only isolate heat, but also accumulate heat. Not only can it enhance the heat dissipation surface area, but also it can increase the air circulation. This airborne effect can also be achieved by reducing the outer diameter of the hollow cup, or by increasing the internal cavity. Compared with the solid cup, the hollow cup can use the air flow to emit heat, more effectively reduce the temperature, not easy to overheating, so as to protect the internal motor. There is air flow on the inner and outer surfaces of the copper plate coil, which is better than the heat dissipation of the slot rotor coil. The traditional enameled wire is embedded in the groove of the silicon steel sheet, the coil surface has little airflow, the heat dissipation is bad, and the temperature rise is large. The ame output power, copper plate coil motor temperature rise is smaller.

Its application range includes robot industry, due to its small size, large power, fast response speed, can be used for robot high speed and smooth movement and precise positioning; medical devices, can be applied to pump, medical laser system, surgical robot, delicate devices need to be miniaturized, and must be extremely accurate, hollow cup motor just meet these requirements; aerospace, widely used in aviation manufacturing, such as aircraft wing structure, flight attitude control system, transmission data sharing system of aircraft fuselage, smart curtains and smart TV.

The above are some professional knowledges on coreless dc motors by VSD Motors. For more relevant information, please contact us.