Patent GB-191502329-A (GB)
Title: Improvements in Controlling Polyphase Electric Motors.
Inventor: BENJAMIN GARVER LAMME
IPC: B60L9/28
Filed: 1915-02-13
Abstract: 2329. Lamme, B. G. Feb. 25, 1914, [Convention date]. Void. [Published under Section 91 of the Act.] Systems for alternating- current motors only.-Relates to the control of a number of polyphase motors. The motors are divided into two sets which, at the lower speeds, are independently energized from the same source, the motors of each set being connected in cascade, while at higher speeds, one set is cut-out, and each motor in the other set is connected to the supply. A switching-arrangement for a four-motor equipment is shown in Fig. 1. The three-phase mains 6, 7, 8 are supplied from a lead 1 through a transformer 2 and phase converter 3. When the controller 5 is in position a, the motors are connected in cascade, the primary of the motor M' being connected to the mains, and the secondary of the motor M<4> being connected to the liquid rheostat R<4>. This gives the lowest speed and highest torque conditions, and the motors may be accelerated by running electrolyte into the rheostat. To obtain the next step, the secondary S<4> is opencircuited, and the controller is moved into position b. The motors M<1>, M<2> are connected in cascade, as also are the motors M3, M<4>, as shown in Fig. 4. The secondaries S<2>, S' are connected to the electrodes of the rheostats R<2>, R', and electrolyte is admitted to the rheostats to diminish the resistance. When the controller is in position c, the primary windings of the motors M', M' are connected to the supply in parallel, and the secondaries are connected to the rheostats R', R'. The remaining motors are disconnected. Certain contacts of the controller may be extended as shown in dotted lines in Fig. 1, and in this case, all the motor primaries are connected in parallel. In a modification, Fig. 2, two motors M<1>1, M<1>2, are employed and the cascade or parallel connexions are made by the controller 99, while, by means of the controllers 97, 98, the motor windings can be arranged to vary the number of poles obtained. At starting, with the controllers in the positions shown, the line switch 40 is closed to connect the primary windings P<1>1< >of the motor M<1>1, to the conductors 6, 7, 8, while the secondaries S<1>1, S<1>2, are connected together through the controllers 97, 99, and the primary P<1>2 of the motor M'z is connected to the rheostat R<1>2 through the controller 98. All the windings are mesh-connected and arranged for the greater number of poles, for instance eight. Electrolyte may be admitted to the rheostat R<1>2, and finally the rheostat may be short-circuited by the switch 43. For the next operating speed, the controller 99 is moved to the position O, thereby connecting the.primary of each motor to the mains, and each secondary to a rheostat. For the highest speed, the controllers 97, 98 are thrown to the positions IV. Each winding is connected in parallel-star, so that the number of poles is only four, and the primaries are connected to the supply and the secondaries to rheostats, as shown in Fig. 8. The motors may have windings arranged for six and four poles and may be interconnected in cascade or parallel to give twelve, ten, eight, or four poles.