Coreless Linear Motor

Linear motors are often simply described as rotary motors flattened, while the working principle is the same. The mover (forcer, rotor) is made by compressing coils with epoxy material; the magnetic track fixes magnets (usually high-energy rare-earth magnets) on steel. The motor's mover includes coil windings, Hall element circuit board, thermal regulator (temperature sensor monitors temperature), and electronic interface. In rotary motors, the rotor and stator require rotary bearings to support the rotor to ensure the air gap between the relatively moving parts. Similarly, linear motors require linear guides to maintain the mover's position in the magnetic field generated by the magnetic track. Similar to how encoders in rotary servo motors are mounted on the shaft to provide position feedback, linear motors require a feedback device for linear position feedback -- a linear encoder, which directly measures the load's position to improve the load's position accuracy.

The control of linear motors is the same as that of rotary motors. Like brushless rotary motors, the mover and stator have no mechanical connection (brushless). Unlike rotary motors where the rotor rotates and the stator position remains fixed, the linear motor system can be either magnetic track driven or thrust coil driven (most positioning system applications have a fixed magnetic track and a moving thrust coil). For motors using thrust coil movement, the weight ratio of the thrust coil to the load is small. However, high-flexibility cables and their management system are required. For motors using magnetic track movement, it needs to bear not only the load but also the mass of the magnetic track, but no cable management system is needed.
 

TECHNICAL DATA

Peak Thrust: 70 - 4170 N
Continuous Thrust: 19 - 840 N
Maximum Speed: 5 - 6.6 m/s
High Thrust with Low Current
No Attraction, No Cogging Effect
No Iron Loss, Low Heat Generation
 

NOTE

1. Choose the appropriate operating speed. The operating speed of a linear induction motor is related to the synchronous speed, which is proportional to the pole pitch. Therefore, the selection range of the pole pitch determines the selection range of the operating speed. A pole pitch that is too small will reduce the slot utilization rate, increase the slot leakage reactance, and reduce the quality factor, thus reducing the motor's efficiency and power factor. The lower limit of the pole pitch is usually 3 cm. The pole pitch can be unlimited, but when the motor's output power is fixed, the longitudinal length of the primary iron core is limited; at the same time, in order to reduce the longitudinal edge effect, the number of poles of the motor cannot be too small, so the pole pitch cannot be too large.
2. Have appropriate thrust. Rotary motors can adapt to a very large thrust range. By matching different gearboxes with rotary motors, different speeds and torques can be obtained. In low-speed situations, the torque can be increased by tens or hundreds of times, so that a very small rotary motor can drive a very large load, of course, power is conserved. Linear induction motors are different; they cannot use gearboxes to change speed and thrust, so their thrust cannot be amplified. To obtain a larger thrust, one can only rely on increasing the size of the motor. This is sometimes uneconomical. Generally speaking, in industrial applications, linear induction motors are suitable for driving light loads.
3. Have appropriate reciprocating frequency. In industrial applications, linear induction motors perform reciprocating motion. In order to achieve higher labor productivity, a higher reciprocating frequency is required. This means that the motor must complete its stroke in a shorter time; within one stroke, it must go through the acceleration and deceleration process, which is to start and brake once. The higher the reciprocating frequency, the greater the acceleration of the motor, and the greater the thrust corresponding to the acceleration. Sometimes, the thrust corresponding to the acceleration is even greater than the thrust required by the load. The increase in thrust leads to an increase in the size of the motor, and the increase in its mass causes a further increase in the thrust corresponding to the acceleration, sometimes resulting in a vicious cycle.
4. Have appropriate positioning accuracy. In many applications, the motor's movement is stopped by mechanical limit switches when it reaches its position. In order to reduce the impact when reaching the position, mechanical buffer devices can be added. In the absence of mechanical limit switches, a relatively simple positioning method is to control the motor for reverse braking or regenerative braking before reaching the position through a travel switch, so that it stops when it reaches the position.