Han's Motor's linear motor is popular science

A linear motor is a transmission device that converts electrical energy directly into linear motion mechanical energy without the need for any intermediate conversion mechanism.

What are the common types of linear motors?

Categorized by how it works

DC motors, asynchronous motors, synchronous motors and stepper motors, etc

Classified by structural form

Unilateral flat motor, bilateral flat motor, disc motor, cylindrical/tubular motor, etc

Flat plate linear motors

The core is mounted on a steel laminated structure and then mounted to an aluminum backplate, which is used to direct the magnetic field and increase thrust. The suction force generated between the magnetic rail and the mover is directly proportional to the thrust generated by the motor, and the laminated structure results in the joint force. Care must be taken when attaching the movers to the magnetic rails so as not to be injured by the suction between them.

U-shaped trough linear motor

There are two parallel magnetic rails between the metal plates and both facing the coil mover. The mover is supported by a rail system between the two magnetic rails. The mover is non-steel, meaning there is no suction and no interfering force is generated between the magnetic rail and the thrust coil. Non-steel coil assemblies have a small inertia that allows for very high accelerations. The coil is generally three-phase, brushless commutation. The motor can be cooled by air cooling to achieve performance enhancements. There are also water-cooled ones. This design minimizes flux leakage, as the magnets are mounted face-to-face in a U-shaped trough. This design also minimizes the damage caused by the strong magnetic attraction.

This design of the rails allows for a combination to increase the stroke length, limited to the operational length of the cable management system, the length of the encoder, and the ability to mechanically construct large, flat structures.

Cylindrical moving magnet linear motor

The mover is a cylindrical structure. Motion along a cylinder with a fixed magnetic field. This motor was first discovered for commercial application, but could not be used in applications where space-saving flat plate and U-groove linear motors were required. The magnetic circuit of a cylindrical moving magnet linear motor is similar to that of a moving magnet actuator. The difference is that the coil can be duplicated to increase the stroke. A typical coil winding is composed of three phases, and a Hall device is used for brushless commutation. The thrust coil is cylindrical and moves up and down along the magnetic rod. This construction is not suitable for applications that are sensitive to magnetic flux leakage. Care must be taken to ensure that the fingers do not get stuck between the magnetic rod and the attractive sides.

One potential problem with the design of tubular linear motors arises when the stroke increases, because the motor is fully cylindrical and moves up and down along the magnetic rod, with the only points of support at both ends. Ensure that the radial deviation of the magnetic rod does not cause the magnet to contact the thrust coil, and there is always a limit to the length of the thrust coil.

Voice coil motor

It is named because its structure is similar to the voice coil of a horn, and it has the characteristics of high frequency response and high precision. This type of motor is divided into cylindrical voice coil motors and oscillating voice coil motors, which are also known as cylindrical linear motors.

The structure of a linear motor

It mainly includes three parts: stator, mover and support wheel for linear motion. In order to ensure that there is a good electromagnetic field coupling between the stator and the mover within the travel range, the core length of the stator and the mover is unequal, and the stator can be made into two forms: short stator and long stator. Due to the high cost and high operating cost of long stator structure, it is rarely used. The linear motor is the same as the rotating magnetic field, the stator core is also made of silicon steel sheets, the surface is cogged, and the groove is embedded with three-phase, two-phase or single-phase windings.

The linear motor is to straighten the primary deployment of the traditional cylindrical motor, change the closed magnetic field of the primary to the open magnetic field, and the stator part of the rotating motor becomes the primary of the linear motor, and the rotor part of the rotating motor becomes the secondary of the linear motor. If the primary is fixed, the secondary can do linear motion along the direction of the traveling wave magnetic field movement, and the feed mode of direct drive of the linear motor of the high-speed machine tool can be realized, and the primary and secondary stages of the linear motor are directly installed on the workbench and the bed of the high-speed machine tool respectively. Since the drive chain of this feed transmission method is shortened to 0, it is called the "zero transmission" of the machine tool feed system.

The working principle of a linear motor

In linear motors, which are equivalent to the stator of rotating motors, are called primary; It is equivalent to the rotor of a rotating machine, which is called a secondary. The primary medium communicates with communication, and the secondary moves in a straight line along the primary under the action of electromagnetic force. At this time, the primary should be very long, extending to the position that the movement needs to reach, and the secondary does not need to be so long, in fact, the linear motor can make the primary very long and the secondary very long, both the primary fixed, the secondary mobile and the secondary fixed, the primary moving.

Linear induction motors are evolved from rotary motors. When a symmetrical sinusoidal alternating current is fed through a three-phase or multi-phase winding on the primary side, an air-gap magnetic field is generated. When the longitudinal edge effect caused by the breaking of both ends of the core is not taken into account, the distribution of this air-gap magnetic field is similar to that of a rotating motor, and is sinusoidally distributed in a straight direction.

Advantages of linear motors

1. Simple structure

The linear motor does not need to go through the intermediate conversion mechanism and directly produces linear motion, which greatly simplifies the structure, reduces the kinetic inertia, and greatly improves the dynamic response performance and positioning accuracy. It also improves reliability, saves costs, and makes manufacturing and maintenance easier. Its initial level can be directly part of the organization, and this unique combination makes this advantage even more apparent.

2. High acceleration

Linear motor drives have a significant advantage over other lead screw, timing belt and rack and pinion drives.

3. It is suitable for high-speed linear motion

Because there is no centrifugal force, common materials can also achieve high speeds. If the gap between the primary and secondary stages is kept by air cushions or magnetic pads, there is no mechanical contact during movement, so there is no friction and noise in the moving part. In this way, there is no wear and tear on the transmission parts, which greatly reduces mechanical losses and avoids noise caused by towing cables, steel cables, gears and pulleys, etc., thus improving the overall efficiency.

4. High utilization rate of primary winding

In the tubular linear induction motor, the primary winding is cake type, and there is no end winding, so the winding utilization rate is high.

5. No lateral edge effect

The transverse effect refers to the weakening of the magnetic field at the boundary caused by transverse breaking, while the cylindrical linear motor has no transverse disconnection, so the magnetic field is evenly distributed along the circumferential direction.

6. Easy to adjust and control

By adjusting the voltage or frequency, or changing the secondary material, different speeds and electromagnetic thrust can be obtained, which is suitable for low-speed reciprocating operation.

7. Strong adaptability

The primary core of the linear motor can be sealed into a whole with epoxy resin, which has good anti-corrosion and moisture-proof performance, and is convenient for use in the environment of moisture, dust and harmful gases; Moreover, it can be designed into a variety of structural forms to meet the needs of different situations.

Han's Motor's linear motor is popular science

Han's Motor's linear motor is popular science

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