Technical Guide Line

What are the advantages and disadvantages of slotless BLDC micro motor?

Compared with ordinary DC motor, Slotless BLDC micro motor adopts slotless rotor which has the advantages of smaller volume and lighter weight. The advantages and disadvantages of slotless BLDC micro motor are briefly described in below.

Advantages of slotless BLDC micro motor

1.High power density : the power density of the slotless BLDC micro motor is the ratio of output power to weight or volume. The slotless rotor is lighter than the ordinary iron core rotor. The slotless rotor eliminates the eddy current and hysteresis loss generated by the iron core rotor, improves the efficiency of the micromotor and ensures high output torque and output power.

2.High efficiency : the reason for the high efficiency of micro motor is that the slotless rotor has no eddy current loss and hysteresis loss, and the resistance is also very small, reducing the copper loss.

3. No torque hysteresis : the slotless rotor has no hysteresis loss, so it reduces the fluctuation of speed and torque.

4. No cogging effect : ordinary micro electric machine produces cogging effect under the interaction between slot and magnet, which is eliminated by slotless BLDC motor, so cogging effect and torque hysterisis will not exist.

5. Low starting torque : due to no hysteresis loss and no cogging effect, the starting torque is very low and usually the bearing load is the only obstacle.

6. There is no radial force between rotor and stator of this micro motor : BLDC motor without iron core rotor has no radial magnetic force of rotor and stator. In some application products, the radial force of rotor and stator will cause rotor instability. Reducing radial force can improve the stability of rotor.

7. Smooth speed curve and low noise : the rotor without iron core reduces the harmonic of torque and voltage. Because there is no AC field in the micro motor, there is no AC noise, only the noise generated by bearing and air flow and the vibration caused by non sine wave current.

8. High speed coil : when the micromotor is running at high speed, the inductance value parameter is important. A small inductance value will reduce the starting voltage. By increasing the number of poles and reducing the thickness of the shell, the inductance value helps to reduce the weight of the micromotor and improve the power density.

9. Fast response : due to the low induction value of micro motor, the fast response of current to voltage fluctuation, the small moment of inertia of rotor, and the response speed of torque and current are the same, the acceleration of rotor is about twice that of ordinary iron core motor.

10. High peak torque : the ratio of peak torque to continuous torque of micro motor is very large because the torque constant is constant when the current rises to the peak and the linear relationship between current and torque can make the micro motor produce a large peak torque. After the ordinary iron core DC motor reaches saturation, the torque of the DC motor will not increase no matter the current increases.

11. Excellent heat dissipation : there is air flow on the surface of the slotless rotor which is better than the heat dissipation performance of the iron core rotor. The enameled wire of the iron core rotor is embedded in the silicon steel slot. The air flow on the coil surface is less and the temperature rise gets higher. Under the same power output conditions, the temperature rise of the slotless BLDC micro motor is smaller.

Disadvantages of slotless micro motor

When the slotless BLDC micro motor is in a static state, such as one phase of the winding is cut off or the power supply is cut off and one phase is connected to the power supply, the two magnetic field points generated by the winding are equal in size and opposite in direction. The rotating magnetic field and the torque generated by the rotor are equal in size and opposite in direction, which offset each other. The motor cannot be started under zero starting torque, which is the disadvantage of the slotless motor.

The above is the introduction of "what are the advantages and disadvantages of slotless BLDC micro motor".

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