Improvements in Control Systems for Electric Motors

16,319. Hall, A. J., and Riley, L. G. July 9, 1913, [Convention date]. Master control systems, for alternating-current motors only.-In a system of control for singlephase motors where the motors are connected to successive tips from a transformer, resistances are connected in circuit with the taps, and the switches employed are interlocked so that they can only operate in a predetermined sequence. Current is supplied to the auto-transformer 7 from the trolly 1 through the coil of an overload trip 25 and the line switch 24. The motors 3, 4 with their fields 5, 6 are connected to the reversing-switch 21 as shown, and the coil of a limit switch 22 is included in the circuit of one motor. Three tappings 8, 9, 10 are taken from the transformer, and resistances 11, 12, 13 are connected to them, the resistance sections being associated with switches 14, 16, 18 respectively, to connect them in circuit, and with switches 15, 17, 19 to short circuit them. The insertion of a plug in the control circuit completes a circuit from a battery through the interlock 44 and the coil 45, thereby closing the line switch 24. The movement of the master controller into its first position causes the closure of the motor switch 20 and its interlock 52, thereby completing the actuating-circuit of the switch 14 through interlocks 56, 58, 60, 52. The switch 14 closes and connects the motors to the tap 8 through the resistance 11. When the current falls to the value at which the contact 64 of the limit switch 22 drops, the circuit of the actuating-coil 65 of the switch 15 is completed through interlocks 66, 68, 64. The switch 15 closes to short-circuit the resistance 11 and so establishes the first running position. It also closes its own maintaining- circuit through the interlock 66. When the master controller is moved to its second position, the actuating-circuit of the switch 16 is completed, and this switch connects the motors to the tap 9 through the resistance 12. The closing of the switch 16 causes the interlock 56 to break the circuit of the coil 54, and the switch 14 therefore opens. When the limit switch 22 operates, the switch 17 closes to short-circuit the resistance 12. In the third position of the master controller, the switch 18 closes, connecting the motors to the tap 10 through the resistance 13, and the switch 16 opens. The switch 19 then closes to short-circuit the resistance, so that the motors run at full speed. The master controller may be moved from zero to its th