Patent GB-190416662-A (GB)
Title: Improvements in Electric Motor Control Systems
Filed: 1904-07-28
Granted: 1905-06-08
Abstract: 16,662. British Thomson-Houston Co., [General Electric Co.]. July 28. Dynamos, regulating; motors, controlling.-In a control system for a group of motors of which the armatures are connected in series, a controlling - switch varies the field strength of the generator and of the motor, and the arrangement of circuits is such that, when one motor is cut out, the field of the other motors can no longer be weakened. A generator G, shown as a compoundwound machine, supplies current to the armatures of the two motors M, M<1>, the fields of which, and also the field of the generator, are separately excited from the mains e, e'. The main controller switch D opens and closes the armature circuits, and regulates the current through the fields of the generator and of the motors, the motor fields being provided with cut-out switches F, F<1>, and the motor armatures with switches A. The switch D is provided with two sets of stationary contacts d<1>-d<21> and d<22>-d<32>, connected to the resistance R and displaced by 180‹ with respect to each other. In the off' position of the controller D, as shown, the armatures of the motors are connected together in series with the resistance r, while the fields are connected with full strength to the mains e, e'. This arrangement of circuits causes the motors to be brought to rest immediately upon turning the switch D to its opan position, and this braking- circuit is disconnected at the contact d<15> or d<19> as soon as the switch D is moved from the 'off' position. When the movable contacts are moved to the left to start the motors with a given direction of rotation, at the first step the stationary contactfingers engage the movable contacts in the position 40, and the following circuits are closed, from the left-hand brush of the generator G through the circuit-breaker c and contact d<21> to the contact d<15>, switch A, motor armature M, switches A, motor armature M', lower switch A, blow-out coil B, and contacts d<19>, d<17>, through the series field, and back to the generator. The circuit of the generator field is from the line e to the generator field g, lower terminal of the resistance R, through the entire resistance to the contact-fingers d<4>, d<3>, and to the line-wire e'. As the motion of the movable contacts is continued to the position 39, a section of the resistance R is short - circuited by the contact-finger d<2>', and each further step cuts out resistance until, in the position 20, the resistance R is entirely cut out and the generator G is fully excited. In passing further to the left, from the position 21 to the position 20, a connection is established between the contact - fingers d<1>, d<2>, which connects the left-hand terminal of the gene. rator field g to the line e<1> independently of the resistance R, and at the same time connection between the contacts d<3>, d<4> is broken, thereby breaking the connection between the line e<1> and the left-hand terminals of the motor fields. A second connection between these fields now remains through the resistance R, and further movement causes resistance again to be introduced in the motor fields, and so the speed of the motors is increased. The weakening of the field is limited by the contact d<22>, which serves to keep a portion of the resistance R in circuit. If one of the motors, say M<1>, is injured, it is thrown out of circuit and a short-circuit provided in its place by throwing the switch A<1> upwards into engagement with the contacts a and by opening the switch F<1>, which permits the two spring clips f<1> shown in detail in Fig. 2 to close, which connects the line e<1> directly to the left-hand terminal of one of the motor fields, so that the remaining field is excited at full strength, and cannot be controlled by the controller D, or excessive speeds would result. Discharge resistances r<2> are provided for the motor fields, and the resistances r' are arranged to be automatically inserted in the armature circuit immediately before opening that circuit. The invention is particularly applicable to controlling a group of motors which operate a turret.