Coreless motor structure principle, advantages and disadvantages, model and service life

With the continuous development of science and technology, motor technology is also constantly innovating. Especially now that the industrial field continuously puts forward higher expectations and requirements for the servo characteristics of the motor, the hollow-cup motor has emerged as the times require. The hollow-cup motor uses an iron-core rotor. This novel rotor structure completely eliminates the power loss caused by the formation of eddy currents in the iron core, and greatly improves the servo characteristics of the motor. Since the coreless motor is so powerful, the editor of Xianji.com will explain the structure principle, advantages and disadvantages, model and service life of the coreless motor in detail for you.

1. The structure principle of coreless motor

The coreless motor uses a coreless rotor, also called a coreless rotor, which breaks through the traditional motor rotor structure in structure. Coreless motors are DC permanent magnet servo and control motors, and they can also be classified as micro motors.

1. Coreless motor structure

The structure of the hollow cup motor is: back cover, terminal block, brush end cover, brush, commutator, cup winding (rotor), shaft, gasket, sliding bearing, housing, magnet (stator), flange, Locating ring.

The stator is composed of a permanent magnet, a shell and a flange. The shell provides a constant magnetic field, so that the motor has no iron loss. There are no soft magnetic teeth. The torque produced is uniform, and it can run smoothly even at low speeds. At higher speeds, the motor can reduce vibration and noise. Rotor with windings and commutator. The windings are connected to the shaft via so-called commutating plates. The coil moves in the air gap between the magnet and the housing. The reversing system uses a pair of precious metal brushes to reduce brush sparks. Reduced brush sparks produce less electromagnetic emissions.

2. Principle of coreless motor

The hollow-cup motor breaks through the traditional rotor structure of the motor in structure, and uses an iron-core rotor, also called a hollow-cup rotor.

This kind of rotor structure completely eliminates the power loss caused by the formation of eddy currents in the iron core, and at the same time its weight and moment of inertia are greatly reduced, thereby reducing the mechanical energy loss of the rotor itself. Therefore, coreless motors are DC, permanent magnet, and servo micro motors.

Second, the advantages and disadvantages of coreless motors

Advantages of coreless motor:

1. High power density

The power density is the ratio of the output power to the weight or volume. The copper coil type motor is small in size and has good performance. Compared with the traditional coil, the induction coil of the copper plate coil method is lighter.

There is no need for winding and grooved silicon steel sheets, which eliminates the eddy current and hysteresis loss they generate; the eddy current loss of the copper plate coil method is small and easy to control, which improves the efficiency of the motor and ensures a higher output torque and output power.

2. High efficiency

The high efficiency of the motor lies in the fact that the copper plate coil method does not have the eddy current and hysteresis loss caused by the winding and the grooved silicon steel sheet; in addition, the resistance is small, which reduces the copper loss (I^2*R).

3. No torque lag

The copper coil method has no grooved silicon steel sheet, no hysteresis loss, and no cogging effect to reduce speed and torque fluctuations.

4. No cogging effect

The copper coil method has no grooved silicon steel sheet, which eliminates the cogging effect of the interaction between the groove and the magnet. The coil has a structure without an iron core. All the steel parts either rotate together (for example, a brushless motor) or all stand still. (For example, a brushed motor), the cogging effect and torque hysteresis are obviously non-existent.

5. Low starting torque

There is no hysteresis loss, no cogging effect, and very low starting torque. When starting, usually the bearing load is the only hindrance. In this way, the start-up wind speed of the wind turbine can be very low.

6. There is no radial force between the rotor and the stator

Since there is no static silicon steel sheet, there is no radial magnetic force between the rotor and the stator. This is especially important in critical applications. Because the radial force between the rotor and the stator will cause the rotor to be unstable. Reducing the radial force will improve the stability of the rotor.

7. Smooth speed curve and low noise

There is no grooved silicon steel sheet, which reduces the harmonics of torque and voltage. At the same time, since there is no AC field in the motor, there is no noise generated by AC. Only the noise caused by the bearing and airflow and the vibration caused by the non-sinusoidal current.

8. High-speed brushless coil

In high-speed operation, a small inductance value is necessary. The small inductance value makes the starting voltage low. By increasing the number of poles and reducing the thickness of the casing, the smaller the inductance value helps to reduce the weight of the motor. At the same time, the power density is increased.

9. Quick response to brushed coil

The copper plate coil type brushed motor has a fast response to voltage fluctuations due to its low induction value. The moment of inertia of the rotor is small, and the torque is equivalent to the response speed of the current. Therefore, the rotor acceleration is twice that of a conventional motor.

10. High peak torque

The ratio of peak torque to continuous torque is large because the torque constant is constant when the current rises to the peak value. The linear relationship between current and torque enables the motor to produce a larger peak torque. In traditional motors, when the motor reaches saturation, no matter how much current is added, the motor torque will not increase.

11. Sine wave induces voltage

Due to the precise position of the coil, the voltage harmonics of the motor are low; and the structure of the copper plate coil in the air gap makes the induced voltage waveform smooth. Sine wave drive and controller can make the motor produce smooth torque. This feature is particularly useful for slow-moving objects (for example, microscopes, optical scanners, and robots) and precise position control, where smooth operation control is the key.

12. Good heat dissipation effect

There is air flow on the inner and outer surfaces of the copper plate coil, which is better than the heat dissipation of the slotted rotor coil. The traditional enameled wire is embedded in the groove of the silicon steel sheet, the airflow on the surface of the coil is small, the heat dissipation is poor, and the temperature rise is large. With the same output power, the temperature rise of the copper coil type motor is small.

Disadvantages of coreless motor:

When the DC motor is in a stationary state, if one phase of the winding is cut off or the power is cut off and one phase is switched on, the two magnetic field points generated by the winding are equal in size and opposite in direction. Cancellation of each other, the zero starting torque motor cannot start, which is the shortcoming of the hollow cup geared motor.

The shortcoming of the hollow-cup geared motor is a dangerous fault. First, we need to check whether the DC motor is faulty, check whether the power circuit has a disconnect switch, whether there is a fuse, and then check whether the three-phase windings are disconnected. .

In addition, restart the motor. If the motor fails to start and buzzes at the same time, cut off the power supply in time at this time. If the power cable is broken, it is even more to find out when it is broken. If the following clues are good, blow the fuse. You should replace the fuse of the same specification. The starter is faulty. The engine should be carefully inspected and repaired. If one phase is broken, The following is to reconsider well or switch off the winding.

3. Coreless motor model

Coreless motors are divided into two types: brushed and brushless. Brushless coreless motors have no iron core in the rotor, and brushless coreless motors have no iron core in the stator.

Common coreless motor models in the market are: supply diameter Φ4, Φ6, Φ7, Φ8, Φ10, Φ12, Φ15 coreless motors.

Fourth, the service life of coreless motor

The life of the coreless motor is generally 15 to 20 years. The life of the coreless motor generally depends on the maintenance of the user, the quality of the use environment and the electromagnetic, heat, vibration and other factors that the motor receives during use. Coreless motors should be analyzed in detail.

For example, like a general-purpose brushed low-power motor, its life depends mainly on the length of the commutator, bearing, and brushes. After their life ends, they cannot be replaced.

For DC motors, permanent magnet DC motors and other small and medium power motors, their life expectancy depends on the insulation life of the commutator and windings, bearing damage and brush polishing can be replaced, and even the permanent magnet material can be re-demagnetized after demagnetization. Magnetizing, which prolongs the life of the motor, is much cheaper than buying a new motor.

Usually, such as good maintenance, reasonable selection of the capacity and installation form of the coreless motor, etc., will make the service life of the motor reach the designed service life, or even far exceed the design life.