This section provides an overview for coreless motors as well as their applications and principles. Also, please take a look at the list of 6 coreless motor manufacturers and their company rankings.
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Coreless motor is also called iron coreless motor. They are small and light because they do not have an iron core like normal motors. The position of the magnet and coil in a coreless motor is reversed from that of a normal motor, making it a motor born from a truly reversed concept.
The absence of an iron core has the advantage of eliminating the loss caused by magnetic materials, known as iron loss, and eliminates vibration caused by cogging, making it a quiet motor. Both brush and brushless motors are available.
However, the torque is lower because the magnetic force generated is weaker than that of a normal motor.
Coreless motors have the advantage of being small, having low vibration and noise, and also having less electromagnetic interference. Therefore, coreless motors are used in vibration motors that cause vibrations in cell phones, servo motors in radio-controlled vehicles and robots, and other applications.
Because of their excellent responsiveness and controllability, they are also used in surveying instruments, camera lens motors, ultrasonic endoscopes, surgical drills, and other applications. These motors are also indispensable for medical applications. Each manufacturer is developing its own coil winding method and materials.
An ordinary motor consists of a coil wound around an iron core, with a magnet placed outside the coil. Electric current flows through the coil, and the magnetic field generated by electromagnetic induction is used to cause the magnet to rotate.
In coreless motors, on the contrary, the permanent magnet is placed inside and the coil is wound around the magnet in a cup shape using resin, etc. outside the magnet, thereby eliminating the iron core. When an electric current is applied to the coil, it is subjected to Fleming's left-hand rule, and the coil rotates. Since the coil rotates, it is called a rotor.
Coreless motors have less inductance in the number of windings, making them highly efficient motors. They are light in weight and have a small moment of inertia, making them suitable for rapid acceleration and deceleration.
The use of powerful rare earth magnets, such as neodymium magnets for the internal magnet, has led to further miniaturization and increased torque. This helps to reduce size, thickness, and weight.
In coreless motors, each company's technology is evident in the way the coils are wound. The coils are designed to minimize waste and increase efficiency.
Coreless motors are motor consisting of coils and magnets without an iron core (core). A motor with coils wound around a common iron core is called a cored motor.
A brushless motor is a motor that does not use brushes and is rotated by controlling the direction of the electric current by an electronic circuit. DC motors (direct-current motors) require periodic reversal of the direction of the current to keep them rotating, so they are classified according to whether they are controlled by electronic circuits or commutators and brushes.
Both brushed and brushless coreless motors exist. A motor that is coreless and brushless is called a coreless brushless motor. In a brushed motor, the rotor is the coil, and the stator is the permanent magnet. For brushless motors, the opposite is true: the rotor is the permanent magnet, and the stator is the coil.
The iron core accounts for most of the weight of a motor. The absence of an iron core in coreless motors allows them to be smaller and lighter. They also have a small moment of inertia (inertia), resulting in excellent responsiveness and controllability, as well as high motor efficiency and high-speed rotation. In the case of cored motors, the iron core and magnet repeatedly move closer together and farther apart, each time causing cogging, which is the trapping of magnetic force. However, coreless motors have the advantage of smooth and quiet rotation because cogging does not occur.
On the other hand, coreless motors generally have the disadvantage of low torque. The amount of torque is proportional to the current value. To achieve high torque, a large current must be applied, but because the copper wire is thin and there is no iron core, the coil is mechanically weak and a large current cannot be applied. If a large current is applied to coreless motors with a small allowable current value, the heat may deform the coil and lead to motor failure.
*Including some distributors, etc.
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Sinotech is based in Portland, Oregon with offices in China. Sinotech is a distributor for custom-engineered electrical motors, motor components, and mechanical components manufactured in China. Sinotech’s motors include AC motors, DC motors, brushless DC motors, slotless high speed BLDC motors, stepper motors, cordless motors, gear motors, servo motors, and miniature motors. Motor components include laminations, wound coils, armature and field coils, brushes, and communicators. Mechanical components include assemblies, die castings, investment castings, sand castings, shafts, steamed metal parts, tubular metal parts, machined extrusions, plastic parts, rubber parts, and secondary processing.
Orbray was originally founded in 1939 in Japan. Orbray serves the automotive, medical, fashion, information communication, audio, and robotics industries. Orbray develops a variety of products including small motors, fiber optics components, and precision jewelry tools. Applications for Orbray’s products include small robots, diaphragm pumps, inner wall metrology systems, and semiconductors.
Nidec Corporation was founded in Kyoto, Japan in 1973 and is a conglomerate with over 200 subsidiaries. Primary products are hard-disk drive motors and automotive parts, and specializes motors ranging from miniature to gigantic. Nidec’s products are used in robotics, automotive, home appliances, agriculturel equipments well as molding, cutting, and machining equipment and sensors.
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