Patent GB-190321305-A (GB)
Title: Method of and Apparatus for Maintaining Two Electric Motors in Synchronism
Filed: 1903-10-03
Granted: 1904-03-31
Abstract: 21,305. Siemens Bros. & Co., [Siemens & Halske Akt.-Ges.]. Oct. 3. Synchronous movements.-In arrangements for maintaining an electric motor in synchronism with a second motor, as in arrangements for transmitting motion to a distance and in the case of motors working telegraphic apparatus &c., the driving or retarding force of the controlled motor is normally varied positively and negatively by equal amounts in rapid succession ; a small deviation from synchronism causes the maintenance of that forcevariation which tends to reduce it. Larger and gradually-increasing deviations are reduced by means of an increasingly-varied driving-force which remains at its changed value after synchronism is re-established. The small variations in the driving- force of the shunt-wound motor m are produced by closing the circuit of a generator g driven by it either through or round a resistance w, thus decreasing or increasing the load on the motor. The larger variations are produced by varying a resistance k<1> in the field or armature circuit of the motor m. The switch lever a which cuts the resistance w into or out of circuit is operated by a relay r' to which regulating-impulses due to the controlling-motor are supplied from mains l, l<6> through a brush b driven in the direction of the arrow by the motor m. A second relay r' in the circuit of the generator g controls the circuits through which the impulses pass and also the circuits of a motor m<1> which operates the resistance switch k. When the motor m is in synchronism with the impulses, and the armatures a, a<1> are as shown, an impulse flows through the finger 2 of the brush b to the main l<6>, the intermediate circuit comprising the main l, winding 4 of the relay r<1>, lead l<8>, contact d<1> of the armature a<1>, and lead l<7>. The armature a is then reversed, and the resistance w short-circuited ; the generator circuit then includes the winding 7 of the relay r<2> so that the armature a' is also reversed. Similar results follow the passage of further impulses during synchronous working, the resistance w being cut in and out of circuit alternately. When, however, the motor m lags behind synchronism, the impulses pass through the relay winding 5 and the finger 3 to the contact c and main l<6>, the parts being maintained in the position shown until the reduction of the motor load has allowed the speed to rise into synchronism with the impulses. Similarly impulses flow through the finger 1 to the contact c and main l<6> when the motor m is ahead of synchronism, and the armatures a, a' are held in the reversed position with the resistance w out of circuit. The armature a', by means of the contacts d<2>, d' and connections shown, normally causes alternating currents to pass from the battery q through the armature, or the field coil, of the motor m<1>, which is therefore not operated. In the event of a long continued and increasing deviation from synchronism, the armature a<1> remains in one position, and the motor m<1> is driven correspondingly to alter the resistance k' in the circuit of the motor m, and so as to alter its driving-force. The resistance k<1> is shown as applied to the field circuit of the motor m, but may otherwise be applied to the armature circuit, or the motor may be series-wound. The resistance w may also be used to vary the energy supplied to the motor m from the battery.