Coreless motor life_Pros and cons of coreless motor

Coreless motor service life

The life of a coreless motor is generally between 15 and 20 years. The life of a coreless motor generally depends on the user's maintenance, the quality of the operating environment, and the electromagnetic, thermal, vibration and other factors to which the motor is subjected during use. A specific coreless motor should be analyzed specifically.

For example, the life of a general-purpose low-power brushed motor mainly depends on the length of the commutator, bearings, and brushes, which cannot be replaced after their life ends.

For DC motors, permanent magnet DC motors and other small and medium power motors, their service life depends on the insulation life of the commutator and windings. Damaged bearings and polished brushes can be replaced, and even permanent magnet materials can be remagnetized after demagnetization. This extends the life of the motor and is much cheaper than buying a new motor.

Usually, if the motor is well maintained and the capacity and installation form of the coreless motor are properly selected, the service life of the motor will reach the designed service life or even far exceed the designed service life.

Advantages of Coreless Motor

1. High power density

Power density is the ratio of output power to weight or volume. Copper coil motors are small in size and have good performance. Copper coil induction coils are lighter than conventional coils.

There is no need for winding wire and slotted silicon steel sheets, which eliminates the eddy current and hysteresis losses they generate; the eddy current loss of the copper plate coil method is very 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 lies in: the copper plate coil method does not have eddy current and hysteresis losses caused by winding wire and slotted silicon steel sheets; in addition, the resistance is small, which reduces copper loss (I^2*R).

3. No torque lag

The copper plate coil method has no slotted silicon steel sheets, no hysteresis loss, and no cogging effect, which reduces speed and torque fluctuations.

4. No cogging effect

The copper plate coil method has no slotted silicon steel sheets, which eliminates the cogging effect of the interaction between the slots and the magnets. The coil is a structure without an iron core, and all steel parts either rotate together (for example, a brushless motor) or are all stationary (for example, a brushed motor). The cogging effect and torque lag are obviously non-existent.

5. Low starting torque

No hysteresis loss, no cogging effect, very low starting torque. At startup, usually the bearing load is the only obstacle. This method can make the wind turbine start at very low wind speed.

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

Since there are no stationary silicon steel laminations, there is no radial magnetic force between the rotor and stator. This is especially important in critical applications because the radial force between the rotor and stator can cause rotor instability. Reducing the radial force will improve the stability of the rotor.

7. Smooth speed curve and low noise

The absence of slotted silicon steel sheets 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. There is only noise generated by bearings and airflow and vibration caused by non-sinusoidal current.

8. High-speed brushless coil

When running at high speed, a small inductance is necessary. A small inductance value makes the starting voltage low. By increasing the number of poles and reducing the thickness of the casing, a smaller inductance value helps to reduce the weight of the motor. At the same time, it also increases the power density.

9. Fast response brush coil

The copper plate coil brushed motor has a low inductance value and a fast response of current to voltage fluctuations. The rotor's moment of inertia is small, and the torque and current response speed are comparable. 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 remains constant as the current rises to its peak value. The linear relationship between current and torque enables the motor to produce a large peak torque. For traditional motors, when the motor reaches saturation, no matter how much current is added, the motor torque will not increase.

11. Sine wave induced voltage

The motor voltage harmonics are low due to the precise position of the coils, and the induced voltage waveform is smooth due to the copper coil in the air gap. Sine wave drive and controller can make the motor produce smooth torque. This feature is particularly useful in slow moving objects (such as microscopes, optical scanners and robots) and precise position control, where smooth motion control is 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 slot of the silicon steel sheet, and there is little airflow on the coil surface, which is not good for heat dissipation and has a large temperature rise. With the same output power, the copper coil motor has a smaller temperature rise.

Disadvantages of Coreless Motor

When the DC motor is at rest, if one phase of the winding is cut off or the power is cut off and one phase is connected, the two magnetic field points generated by the winding are equal in magnitude and rotate in opposite directions. The torques generated by them and the rotor are equal in magnitude and opposite in direction, which cancel each other out. The motor with zero starting torque cannot start. This is the disadvantage of the hollow cup reduction motor.

The disadvantage of the hollow cup reduction motor is that it is a very dangerous fault. First, we need to check whether the DC motor is faulty, check whether there is a circuit breaker in the power circuit, whether there is a fuse, and then check whether there is any current interruption in each phase of the three-phase winding.

In addition, restart the motor. If the motor is blocked and fails to start, and it buzzes, cut off the power supply in time. If the power cable is broken, it is necessary to check it out. If the fuse is good, replace it with a fuse of the same specification. If the starter fails, the engine should be carefully checked and repaired. If one phase winding is broken, reconsider or replace the winding.