Patent GB-617591-A (GB)
Title: Improvements in and relating to electric motor devices
IPC: H02K26/00
Filed: 1942-09-05
Abstract: 617,591. Electric control systems. TUSTIN, A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Sept. 5, 1942, Nos. 12621 and 17484. [Class 40 (i)] [Also in Group XXXV] An electric motor device which may be used directly as the driving motor of a movable object or as a control device for a driving motor comprises two magnetic elements with polar faces providing two magnetic circuits with gaps of short length normal to the direction of movement, the permeances of the circuits, dependent on the overlap of the polar faces, being varied oppositely by the relative movement of the two elements, which movement is controlled by an exciting winding producing a main flux in each circuit and a control winding by which the main flux in one circuit is increased and, in the other, decreased. The motor which may be arranged for rotary or linear movement, produces a torque or force which is dependent as to direction on the direction of current in the control winding and is substantially proportional thereto over a range of relative movement of the two elements of the motor. In the rotary device shown in Figs. 1 and 2, the stator comprises a pair of bi-polar annular laminated cores 2, 3 slotted diametrically to receive main exciting windings 18, 19 and control windings 20, 21 and 22, 23, the pole faces being uniformly toothed at 8. The rotor comprises two integral parts 9, 10 each having pole faces toothed similarly to the stator faces but displaced in opposite directions from the position of registration with the stator teeth. The main windings 18, 19 are connected in series and produce fields in the same direction in each stator core; the control pairs 20, 21 and 22, 23 are also connected in series, but although each of a pair operates in the same direction on its respective core, the pairs respectively assist and oppose the main excitation in the two cores, or vice versa, depending on the duration of control current. The torques produced on the two portions of the rotor are in opposite directions and the resultant torque is proportional to the control current. Fig. 4 (not shown) comprises a similar arrangement of toothed stators and rotors, but the two magnetic circuits comprise also a common gapped path situated between the two portions of the device and the windings are carried between the two portions instead of in slots in the stator cores. Fig. 6 (not shown) comprises a further modification in which the magnetic circuits are independent. Both portions of the device comprise a pair of annular toothed stator cores, the windings being situated between the cores of each pair. Fig. 7 comprises a modification in which the elements have untoothed polar faces, the stator 60 having four poles and the rotor two. The exciting windings 71 are arranged to produce fluxes in the direction of the full line arrows and the control windings in the direction of the dotted arrows for one direction of control current so that the main flux in poles 62, 64 is reduced and that in poles 61, 63 increased, or vice versa for the other direction of control current. Devices for producing linear motion. Fig. 9 comprises a pair of pot magnets 81, 82 having exciting windings 89, 90 operating in the same direction and control windings 91, 92 which respectively assist and oppose the corresponding exciting winding, or vice versa. The pole faces of the magnets have annular teeth and the linearly movable member is similarly toothed, but normally the teeth opposite magnet 81 and those opposite magnet 82 are displaced in opposite directions with respect to the teeth of the magnets so that the resultant force on the movable member is the difference of the forces exerted by the magnets separately. In order to prevent relative movement of the parts due to inertia when the whole device is moved, a compensating inertia member 93 is linked with both parts. In other modifications, Figs. 11 to 13 (not shown), the two parts of the device comprise stacks of laminations arranged to provide plain or toothed polar faces, the windings being suitably disposed on the stator stacks. The movable member may be supported in bearings or by flexible discs or spiders which may be resilient to provide spring bias. Control systems. In a positional control system, the motor device of the invention is supplied with a voltage dependent in intensity and direction on the misalignment of a control member and a movable object, e.g. by a reversing potentiometer differentially controlled by the control member and object. The said motor device is used to set a motor controller of the nature described in Specification 577,312, [Group XXXVII], whereby a metadyne machine and electric motor are caused to drive the object into positional correspondence. In a system in which an object is required to be driven at a speed corresponding to the setting of a control member, the said member controls the output voltage of a potentiometer which is opposed by a voltage dependent on the speed of the driven object and the resultant is applied to the control windings of the motor device of the invention. The movable member of said device is used to control the torque applied by arrangements for driving the object as described above for positional control systems. The voltage dependent on the speed of the object may be taken from the armature brushes in the cam of an electric driving motor or from a tachometer generator coupled with the driven object. The motor device of the invention may be used directly to drive an object. For example in the control system described in Specification 616,516 it may replace the metadyne and electric motor shown in Fig. 7 thereof.