What is a Linear Motor?

Posted on Dec 21, 2018

Linear Motor

In the metal working industry, a linear motor by definition is an electric motor that has its stator and rotor unrolled, therefore, instead of the emission of a torque (i.e. rotation), the linear motor can emit a linear force along its length.

What is a linear motor?

In the metal working industry, a linear motor by definition is an electric motor that has its stator and rotor unrolled, therefore, instead of the emission of a torque (i.e. rotation), the linear motor can emit a linear force along its length. Importantly, although the force is linear, linear motors are not always linear.



The development of linear motors can be traced back to the 1840s in the United Kingdom. In practical applications, there is a feasible linear induction motor used to drive trains and elevators in the United States. Later, a German engineer built a working model in the 1930s. Then in the late 1940s, the first full-scale working model was built.

In about a century, the development of linear motors began with a concept, then promoted by many talented inventors and engineers in history, and then applied in industry. These linear motors are all low acceleration linear motors.


Compared with the concept of BLDC motors

Another common type compared to linear motors is BLDC motors. The BLDC motor is a synchronous motor driven by direct current through an inverter that sends out alternating current to excite each phase of the motor through a closed-loop controller. At the same time, the controller provides current pulses to the motor windings to control the torque and speed of the motor. Generally speaking, the structure of a brushless motor is similar to a permanent magnet synchronous motor (PMSM for short), and the former can be regarded as a switched reluctance motor or an induction motor, but not a synchronous motor.

Read More: BLDC Motors & Automation


Advantages of the BLDC

Regarding the advantages of brushless motors compared to brushed motors, the former design has a higher power-to-weight ratio, higher speed, better electronic control and lower maintenance costs. Based on these advantages, brushless DC motors are widely used in many scientific applications. For example, servo brushless motors (DC and AC) are commonly used in robotics.

Recently, AC servo motors have also been widely used because control becomes easier than before and can still withstand higher torque. With the introduction of BLDC motors, industrial robotic arms can now move heavy objects with high precision, but at a lower cost than other alternative solutions. Therefore, in the industrial field, many robotic arms are equipped with brushless DC motors, thus providing the best output quality for the production line. BLDC motors can be used in a wider range of industrial fields, and robot arms are just one of them.


BLDC motor used in the linear motors

Linear motors are devices that can produce linear motion without a transmission system. Conventional transmission systems require many components, such as racks and pinions, ball-and-lead screws, cams, etc.

In a rotary motor, all of the above components are necessary. The technical design of the brushless DC linear motor is a slotted stator with magnetic teeth and a moving actuator. Actuators usually have permanent magnets and coil windings. In order to obtain linear motion, the motor controller attracts the coil windings in the actuator, which causes the magnetic field to activate, thus achieving a linear effect perfectly.


Industrial trend of linear motor

Nowadays, in the fields of automation and 3C consumable electrical appliances, manufacturers tend to purchase machining centers with robot arm to achieve a wider range of applications. The machine tool is the most basic asset of the manufacturer, and plays a vital role in determining the output quality. Linear motors, robot arm and other automation equipment on the machine tool can bring higher performance and efficiency.


BLDC stands out

After inventing the machining center and programmed control system (CNC, computer numerical control), the machining standards became stricter than before. In addition to CNC machining centers, there are CNC turning centers, CNC milling machines, CNC tapping and milling centers, CNC drilling and milling machines, and other customized machineries, which can be integrated with automated systems or semi-automatic systems.


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