When someone says "motor," the image that usually comes to mind for most people is typically a rotating one. However, motors can take different forms, such as linear motors.

Linear motors were invented by Dr. Eric Laithwaite of the University of Manchester in the late 1940s. They were originally designed as low-acceleration devices, but in modern times, this technology has been able to achieve extremely high speeds for automation purposes. This technology has also become the foundation for maglev (magnetic levitation) transportation.

Unlike rotating motors, linear motors do not have a rotor that rotates inside a stator. Instead, they have a carriage that moves back and forth along a track.

The structure of a linear motor is the same as that of a rotating three-phase motor, but it is open and flat. Configuring a servo drive for a linear motor is the same as configuring a drive for a rotating motor.

A linear motor consists of permanent magnets with alternating polarities and a moving carriage equipped with three-phase coils. The direction of the current passing through these coils magnetizes two phases (north and south), which respectively pull or push the motor along the motor track.

Linear motors are not the only way to achieve linear motion control. In many cases, the same motion can be achieved using rotating motors with ball screws or linear actuators. Ball screws and linear actuators are usually much cheaper than linear motors, so some people may ask:

Short answer: Linear motors are used for fast movement, environmental adaptability, and extremely high precision. Ball screws and linear actuators are used for high force and low cost.

Long answer: As we have seen, the structure of a linear motor is the same as that of a brushless rotating motor but flattened. When used in an application, the load is connected to a carriage that moves along permanent magnets. Since there is no transmission device, this is a direct drive system, which gives it incredible responsiveness and speed, with no backlash. The disadvantage is that the force is limited by the strength of the magnetic force and the amount of power the motor coils can carry.

On the other hand, ball screws and linear actuators use rotating motors connected to mechanical transmission systems to convert rotational motion into linear motion. Due to the involvement of transmission devices, the available force is much higher than that of linear motors. The shorter the lead on the ball screw, the greater the force generated, but the speed will be sacrificed. In many such systems, there will also be reaction forces, which can reduce precision.

Linear motors are used in direct-drive applications where speed and precision requirements exceed those that rotating motors and mechanical actuators can provide.