Motor windings give tighter control

California Linear Devices, Carlsbad, Calif., uses high-response windings to gain tight control and accuracy in their motors. They use series windings rather than a series-parallel wound coil. This restricts velocity ripples to less than 1% and yields positioning resolutions to 1 mm. The winding configuration also minimizes effects from outside disturbances and lets the motor reach peak force in 700 msec.

The compact motor relies on permanent rare-earth magnets and three-phase direct-drive, brushless dc technology to generate between 50 and 1,200-lb peak force. Stator length and diameter set the force level, while shaft length determines stroke, which ranges from 2 to 20 in. for standard models. In many applications, this tubular linear motor is replacing hydraulics and pneumatics, as well as electromechanical systems with many moving parts and limited programmability. It is also an alternative to linear motors with external bearing systems that can cost more than the motors themselves.