Application of d.c. linear machines as short-stroke and static actuators

An actuator is described which is suitable for short-stroke and static applications based on the use of a d.c. linear motor, without the need for a commutator. For such an arrangement, the output-force/displacement characteristics are calculated and the analytical results are shown to compare favourably with experimental results obtained on 2-pole and 3-pole machines. A simple form of control of force/displacement characteristics, based on the use of a graded armature winding, is described. Results are included for such an actuator designed for mechanical valve operation. The results obtained indicate that the d.c. linear actuator is an attractive alternative to the linear-induction actuator, particularly in applications where ease of control is a primary factor.