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The structure principle, advantages and disadvantages, models and service life of coreless motor
TIME:2021-09-15 17:16     PV:436

    With the continuous development of science and technology, the motor technology is also constantly innovating. Especially nowadays, the industrial field has continuously raised higher expectations and requirements for the servo characteristics of electric motors, and coreless motors have emerged at the historic moment. The coreless motor uses an ironless rotor. This novel rotor structure completely eliminates the power loss caused by the eddy current formed by the iron core, and greatly improves the servo characteristics of the motor. Since the function of the coreless motor is so powerful, the following editor of Xianji Network will explain in detail the key knowledge of the structure principle, advantages and disadvantages, models and service life of the coreless motor.


The structural principle of coreless motor

The coreless motor uses a coreless rotor, also known as a coreless motor, which breaks through the structure of the traditional motor rotor structure. The coreless motor is a DC permanent magnet servo and control motor, which can also be classified as a micro special motor.

1. Coreless motor structure

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

The stator is composed of permanent magnet, shell and flange. The housing provides a constant magnetic field, making the motor free of iron losses. No soft magnetic teeth. The generated torque is uniform, which makes the operation smooth even at low speeds. At higher speeds, the motor can reduce vibration and reduce 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 commutation 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 coreless motor breaks through the structure of the rotor of the traditional motor in structure, and uses an ironless rotor, also called a coreless rotor.

This rotor structure completely eliminates the power loss caused by the eddy current formed by the iron core, and its weight and rotational inertia are greatly reduced, thereby reducing the rotor's own mechanical energy loss. Therefore, the coreless motor belongs to DC, permanent magnet, servo micro special motor.

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 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 wire and slotted silicon steel sheet, which eliminates the eddy current and hysteresis loss they produce; the eddy current loss of the copper plate coil mode is small and easy to control, which improves the efficiency of the motor and ensures higher output torque and output power.

2. High efficiency

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

3. No torque lag

The copper plate 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 plate coil method has no grooved silicon steel sheet, which eliminates the cogging effect of the interaction between the groove and the magnet. The coil is a structure without an iron core, and all steel components either rotate together (for example, a brushless motor), or are all stationary (For example, brush motors), cogging and torque hysteresis are clearly absent.

5. Low starting torque

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

6. No radial force between rotor and 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 silicon steel sheet with grooves, reducing 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 bearings and airflow and the vibration caused by 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 chassis, the smaller inductance value helps reduce the weight of the motor. At the same time, the power density is increased.

9. Quick response brushed coil

The brush motor of the copper plate coil method has a low response value and the current responds quickly to voltage fluctuations. The rotor's rotational inertia is small, and the response speed of torque and current is equivalent. Therefore, the acceleration of the rotor is twice that of the conventional motor.

10. High peak torque

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

11. Sine wave induced voltage

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

12. Good heat dissipation effect

There is air flow on the inner and outer surfaces of the copper 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. There is little air flow on the surface of the coil, the heat dissipation is poor, and the temperature rise is large. With the same output power, the temperature rise of the copper plate coil motor is small.

Disadvantages of coreless motor:

When the DC motor is at a standstill, if one phase of the winding is cut off or the power is cut off and one phase is connected to the power supply, the magnetic field points of the windings have the same size and opposite directions. The magnetic fields rotate in the opposite direction, and they have the same torque as the rotor and opposite directions Mutually cancel each other, the zero-start torque motor cannot start, which is the shortcoming of the coreless gear motor.

The disadvantage of the coreless geared motor is a very dangerous failure. First of all, we need to check whether the DC motor is faulty, whether the power circuit has a circuit breaker, and whether there is a fuse, and then check whether the three-phase windings have any current interruption .

In addition, restart the motor. If the motor is blocked and fails to start, it will buzz at the same time. At this time, cut off the power in time. If the power cable is disconnected, it will be found when it is broken. If the following clues are good, the fuse should be replaced. The starter of the same specification should be replaced. The engine should be carefully checked and repaired. If one phase of the coil is blocked, The following is to reconsider or exchange the cut winding.

Coreless motor model

The coreless motor is 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 industrial grade coreless motor models are: supply diameter Φ10, Φ12, Φ15, Φ16, Φ17, Φ18, Φ20, Φ22, Φ24, Φ28, Φ30, Φ32 coreless motor.

Coreless motor service life

The life of the coreless motor is generally 15 to 20 years. The life of the coreless motor depends largely on the user's maintenance, the quality of the use environment and the electromagnetic, heat, vibration and other factors that the motor is subjected to in use. The specific The coreless motor should be analyzed specifically.

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

For small and medium power motors such as DC motors and permanent magnet DC motors, their life depends on the insulation life of the commutator and windings. Bearing damage and brush polishing can be replaced, even after the permanent magnet material is demagnetized. Magnetizing, which extends 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.