831,667. Control of A.C. motors. SOC. TECHNIQUE POUR L'INDUSTRIE NOUVELLE S.A. STIN. Aug. 22, 1957 [Aug. 22, 1956], No. 26489/57. Class 38 (3). [Also in Group XXX] In an electric circuit for controlling the operation of a reversible two-phase motor driving a member in reversible mechanical movement between two end positions, one of the motor phase windings in each end position is connected between one phase of the supply and a common supervisory line whilst the other phase winding is connected between the other supply phase through a check line in series with an operation checking circuit to the supply neutral. Switch contacts, controlled by movement of the motor-driven member, are arranged so that during operation the motor is energized in two-phase fashion without interruption over the entire run from one end position to the other and on starting of the movement away from one end position the operation checking circuit is at first connected with both its poles at the same potential and then, as the member approaches its other end position, one pole is disconnected so that a current flows through the checking circuit to initiate termination of the driving current from the motor. In the arrangement shown in the Figure for operating railway switch points, the circuit to the left of the chain dotted line is the circuit at the control point and to the right are parts situated at the railway switch point, the two parts being connected by conductors L1, L2, L3, L4. The points driving motor is a two-phase motor with stator windings M1, M2. The movement of the points by the motor operate switches DA1, DA2, DB1, DB2, such that, on movement from one end position (the normal position being shown), the moving contact DA moves away from DA 1 but before it breaks contact with DA1 it makes contact with DA2. On continued movement contact DB moves away from contact DB2 and on the points reaching the other end position (reverse position) the contact DB1 is closed and DB2 open. Similarly, on movement of the points from the reverse to the normal position DB2 closes before DB1 opens and towards the end of the movement contact DA1 moves away from DA2 finally closing DA1 and opening DA2. The control circuit is a direct current supply and produces a continuous supervisory current fed in at the terminals P, N. The two-phase current for the points operating driving motor is fed from terminals P1, P2 and neutral O. To effect change over of the switch points a manuallyoperated switch U is closed to complete a circuit from the terminals P, N to a voltage reversing relay R having contacts R1, R2, R3. Contacts R, R1, R2 serve to reverse the connections (on energization of a relay V) between the phase terminals P1, P2 and the two motor windings M1, M2. Before relay R is energized the terminal P1 would be connected, if switch V3 is closed, through line L2 to winding M2 and terminal P2 through line L1 to winding M1 On energization of relay R these connections are reversed. The contacts R1,R2 are of the type that on energization of relay R they are thrown over to the position opposite to those occupied and remain in such position until the relay R is again energized to return them to the original position. The third contact R3 connects the winding of the voltage changeover relay V across the direct current source P, N to energize relay V and to close contacts V4 and V5 and to change over contacts V1 and V2, V3. The contact R3 is closed only so long as the relay R is energized. In addition to the two lines L1, L2, the other two lines are the check line L3 and the supervisory line L4. The check line L3 joins the contacts DA1, DB1 through a supervisory solenoid C to contact V3 which is closed in the normal rest position. The armature of the solenoid C operates or forms a device indicating the presence of a current through the solenoid. A circuit for checking the correct operation of the changeover sequence is formed by a relay S deriving its power through a full wave rectifier SR from a transformer ST, the primary winding of which transformer is connected in series with a holding contact S3, of the relay S, and contact V4 between the check line L3 and the neutral O of the supply. In addition the operation checking relay has contacts S1, S2 of which S1 is closed when the relay S is de-energized and opens on energization whilst S2 is normally open and is closed on energization. The contact S1 controls a connection through a contact A3 from the winding of a trip relay T and contacts V2 to the neutral O. The contact S2 controls energization of the winding of an auxiliary relay A from the direct current supply P, N through contact V5. The auxiliary relay A has contacts A1,A2,A3. The contact Al is in parallel with contact S3 and is closed in the rest position of relay A. The contact A2 is in parallel with contact S2 and acts as a holding contact with relay A when relay S is energized. The contact A3 prepares the circuit to the trip relay T, which circuit is completed when relay S is de-energized to close contact S. The relay V is of the kind such that, once energized, the contacts remain in the position in which they have been left, even after the winding is deenergized. The relay T, mechanically interconnected to relay V, on energization restores the contacts V1, V2, V3, V4, V5 to their original position. Specification 683,665 is referred to.