Linear permanent magnet synchronous actuators (LPMSAs) have been proposed for applications in factory automation upgrading. Such actuators utilize high-energy product magnets and are characterized by high thrust density, low losses, small electrical time constant, and rapid response. The main drawbacks of LPMSAs are their high cost owing to the costs of the magnets and the presence of stray magnet fields, especially in single-sided configurations.

Thrust– or position-controlled flat LPMSAs may be used for travels up to about 3 m, with a constant airgap provided either mechanically or via a controlled suspension system. For travel lengths of less than 0.5 m tubular configurations may be preferred, since tubular structures make better use of materials, resulting in a compact actuator.

CONSTRUCTION DETAILS

LPMSAs may be flat single-sided or double-sided or may have a tubular structure. In either of these configurations, the primary may constitute the mover. On the other hand, the actuator may have moving magnets. The core of the primary of a flat LPMSA is made of longitudinal laminations with uniformly distributed slots, which house the windings. Often, the windings are three-phase distributed windings having one to four slots/pole per phase (q = 1, 2, 3, or 4). These windings are similar to those of induction-type actuators presented in Chapter 3. Because the windings are located in open slots, the effective airgap becomes considerably greater than the actual airgap.

In tubular structures the laminations of the primary core may be either longitudinal or disk-shaped as in linear induction actuators.