Improvements in and relating to the Control of Alternating Electric Current Motors of the Commutator Type in their Application to the Driving of Machine Tools and other similar Drives.

摘要

3096. British Thomson-Houston Co., [Allgemeine Elektricitõts Ges.]. Feb. 11. Electrically - actuated.-In driving, by alternating- current commutator motors, machine tools, such as planing - machines and other apparatus or machines in which different speeds are necessary during different periods, the motor is controlled so that, during the working period of the machine, it runs with a shunt characteristic, while, during the idle or return period, it runs with a series characteristic. One form of motor for the purpose is provided with a stator winding a, short-circuited brushes b and exciting brushes e ; the lower brush e is connected to a series exciting transformer t and the upper brush e to a switch s. In the position of the switch s shown, the motor runs with a series characteristic. On moving the switch s on to the contact s1, the upper brush e is connected to a part of the stator winding a, which may be variable, and the motor runs with a shunt characteristic. For large motors, the switch s in its open position may connect the upper brush e to the left-hand brush b, as shown in dotted lines. The switching may be made dependent on the movement of the machine tool. The motor may be controlled so that the working speed or a less speed is initiated before the end of the idle-speed period.