Patent GB-865439-A (GB)
Title: Improvements in or relating to apparatus for maintaining two devices in synchronism when in operation
IPC: H02P5/49
Filed: 1957-04-12
Abstract: 865,439. Electric synchronous movements. BAUER G.m.b.H., E. April 12, 1957 [April 14, 1956], No. 11970/57. Class 40(3) [Also in Group XXXV] An arrangement for maintaining a leader device and a follower device in approximate synchronism comprises a first impulse generator coupled with the leader device and responsive to the speed thereof, and a second impulse generator coupled with a follower device and responsive to the speed thereof, together with a control circuit controlling the speed of the driving motor of the follower device in response to any difference in the phasing of the first and second impulse generators and an operating circuit provided in association with the first impulse generator includes relay means responsive to voltage conditions which occur only when the leader device is in operation and having normally open contacts in the circuit of the driving motor of the follower device. The primary or leader motor 9 having an operating circuit (not shown) drives a pulse generator 10 comprising an insulating segment 11 and conducting segment 12 connected by a brush 13 over a conductor 19 to a brush 8 engaging similar segments 6, 7 of a pulse generator 5 driven by the controlled motor 1 energized from mains 4. The generators 5, 10 are connected in parallel in a circuit comprising a battery 15 and a coil 17 of a saturable reactor having an associated coil 3 in series with the motor 1. The conductor 19 includes the primary winding 20 of a transformer whose secondary winding 21 is in an auxiliary circuit comprising a relay 23 having a series rectifier 22 and a shunt capacitor 24. When the primary motor 9 is switched on, the current variations generated in the primary winding 20 by the segments 11, 12 and the battery 15 are fed to the auxiliary circuit and rectified so that relay 23 operates and at closed contact 2 completes the driving circuit for the controlled motor 1. During the rotation of the generator 5 the phase displacements of its insulating and conducting segments 6, 7 relative to the elements 11, 12 of the generator 10 vary the currents through the coil 17 and thereby inversely the impedance of the coil 3. When connection is effected simultaneously to the conducting segments 7, 12 the resistor 14 and winding 20 are connected in parallel so that the current through the coil 17 is increased and the motor runs faster. When only the resistor 14 or the winding 20 is connected, the current in the coil 17 is decreased, the impedance of the coil 3 is increased and the motor 1 slows down. The impedances of the coil 3 are chosen so that the speeds of the motor for the two limiting cases are, respectively, slightly above and below the desired synchronous speed. In the arrangement shown in Fig. 2, the generators 35, 37 are in series with a battery 45, the primary 46 of the transformer being connected across conductors 40, 43 and in parallel with the generator 35. Relay 49, operated when the primary motor 36 is set into operation, closes switch 31 to bring in motor 30 having resistors 32, 33 in its operating circuit. Resistor 32 is short circuited to increase the speed of motor 30 to a value slightly above the synchronous speed on the closure of the contact 51 by the operation of relay 44 when the conducting segements 38, 39 are simultaneously contacted by the brushes 41, 42. When the segments are 180 degrees out of phase the circuit of the relay 44 is broken so that resistor 32 is again connected in the circuit of the motor 30 with consequent speed reduction to a value slightly below that of the desired synchronous speed. In a modification, Fig. 3 (not shown), the conducting segment such as 39 of the generator 37 of Fig. 2 is associated by diametrically arranged brushes with the ends of the primary of a transformer having a secondary winding to produce the voltage for operating a relay, such as 49, to complete the circuit of the follower motor. The relative phases of the conducting segments of the generators control the insertion or short circuiting of a single resistor connected in series with the follower motor. In a modification of Fig. 3, Fig. 4 (not shown), the diametrically arranged brushes are connected to the windings of two relays controlling associated contacts arranged in series in the circuit of the follower motor so that in any position of the leader pulse-generator when its motor stops, the circuit of one of the relays is broken so that the follower motor stops immediately. In a further modification, Fig. 5, the pulse generator 152 of the follower device comprises approximately semi-circular conducting segments 158, 159 engaged by brushes 160, 161 connected to brushes 167, 168 associated with the semi-circular segment 166 of the leader pulse-generator 165. The driving circuit of the follower motor 151 includes the switch 155 closed by the operation of the relay 182 in an auxiliary circuit including the secondary winding 180 of a transformer. A centre tapping 184 on the primary winding 179 is connected via a rectifier 186 to an autotransformer 188 connected in series with the mains supply 156, 157 and the ends of the primary winding are connected to brushes 177, 178 so that rotation of the leader generator 165 induces a control voltage in the auxiliary circuit to operate the relay 182. The pulse generator 152 includes two centrifugally operated switches 162, 163 which during the run-up period of the motor 151 close a path short-circuiting the resistor 153 in the motor circuit. When the motor approaches synchronous speed, one of the switches opens so that one only of the conducting semi-circular segments 158, 159 is effective for controlling synchronism in conjunction with the segment 166 of the generator 165. When the speed of the motor 151 exceeds the synchronous speed, both switches 162, 163 open so that the resistor 153 cannot be short-circuited by the generators 152, 165 and the speed drops. If the switch 176 is closed, the resistor 153 is shortcircuited independently of the control circuit, and if the switches 171, 172 are opened, the short-circuiting of the resistor 153 through the pulse generators 152, 165 is prevented.