What are the Characteristics of the Coreless Motor?

1. History and definitions

In 1958, the German Dr.F.Faulhaber developed the oblique winding coil winding technology, and in 1965, it obtained the patent technology of the coreless motor rotor oblique winding coil. coreless motor belongs to the DC permanent magnet servo, control motor, it can also be classified as a micro-special motor. In the structure of the traditional motor rotor structure form, using the use of no core rotor, also called coreless rotor. This novel rotor structure completely eliminates the power loss caused by the vortex formation of the iron core. Because there is no iron loss, so its efficiency is higher than ordinary micro dc motor, its coil is the rotor, rotational inertia is small, easy to control, but no core, rotor coil can only do very thin, or will lose magnetic flux, so the coreless motor power is not big, large also can only do a few hundred watts.

2. structure

It is mainly composed of rear cover, wiring terminal, brush terminal cover, brush, commutator, cup winding (rotor), rotating shaft, gasket, sliding bearing, shell, magnet (stator), flange and positioning ring. 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 available. The resulting torque is uniform to smooth operation even at low speeds. At higher speeds, the motor reduces vibration and noise. Rotors with windings and commutators. The windings are connected to the shaft through a so-called reversing plate. The coil moves in the air gap between the magnet and the shell. The reversing system reduces a reduction of brush sparks using a pair of precious metal brushes. Reduced brush sparks produce less electromagnetic emissions.

3. classify

A. Brush coreless motor: the rotor has no iron core (the rotor is A coil, the stator is A permanent magnet, generally use this).

B. Brushless coreless motor: the stator has no iron core (the stator is a coil, the rotor is a permanent magnet or magnetic steel (made of rare earth permanent magnet material)).

4. Main characteristics and advantages

A. Energy saving characteristics: the energy conversion efficiency is very high, its maximum efficiency is generally more than 70%, some products can reach more than 90% (iron core motor is generally 70%).

B. Control characteristics: quick starting and braking, rapid response, mechanical time constant less than 28 ms, some products can reach within 10 ms (core motor generally above 100 ms); high speed adjustment in the recommended operating area.

C. Drag characteristics: the operation stability is very reliable, the speed fluctuation is very small, as a micro motor, its speed fluctuation can be easily controlled within 2%.

D. 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 inertia of rotation and the torque is comparable to the current. Thus, the rotor acceleration is 2 times that of the conventional motors.

E. Sine wave induced voltage. 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 to operation.

F. 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 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.

5. Application scenario for example

A. Accompangating system that require rapid response. For example, the flight direction of the missile is quickly adjusted, the follow-up control of high rate optical drive, fast automatic focus, highly sensitive recording and detection equipment, industrial robots, bionic prosthetic limbs, etc., coreless motor can well meet its technical requirements.

B. Various aircraft, including aviation, aerospace, model aircraft, etc. The advantages of light weight, small volume and low energy consumption can minimize the weight of the aircraft.

C. It is also used as a generator because of its high energy conversion efficiency; or as a speed generator with its linear operation characteristics; or as a torque motor with a reducer.

D. On medical devices: such as ventilator, dental instruments.

Six, technical difficulties

A. Heat treatment: When the brush coreless motor is running, it will generate heat due to friction, resulting in the overall temperature of the motor to rise, and then affect the service life of the motor. To solve this problem, heat dissipation technology can be adopted to transfer excess heat to the surrounding environment to reduce the motor temperature and extend the service life of the motor.

B. Assembly requirements: Due to the small size of the arm ature, it needs to be strictly controlled in the production process to ensure the consistency of the accuracy of the parts. At the same time, the assembly process is relatively complex, because of the high coordination requirements of each component, not only to ensure the accuracy of the position and Angle, but also to ensure the overall coordination of the motor, to ensure the effective coordination of mechanical properties.

C. Power matching: when using the brush coreless motor, it is often required to carry a certain amount of power. In the motor design, the power demand factors should be fully considered to ensure the matching between the motor and the drive system, and improve the efficiency of the power system of the motor.

D. Electromagnetic compatibility problem: the brush coreless motor works by coupling potential, which is susceptible to the interference of external electric field or magnetic field, and affects the normal operation of the motor. EMI filter and shielding technology can be used to ensure the normal operation of the motor.

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