Patent GB-649169-A (GB)
Title: Improvements in or relating to electric motor control systems
IPC: B21B37/54
Filed: 1948-06-23
Abstract: 649,169. Automatic control systems for rolling mills. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. June 23, 1948, No. 16866. Convention date, June 30, 1947. [Class 38 (iv)] [Also in Group XXXVII] In a control system for a rolling mill in which the reel motor armature is supplied from a separate generator in turn controlled by a regulating generator, and in which the field of the reel motor is controlled by a field regulator responsive to the diameter of the reel, there is also provided an inertia compensation generator which controls the regulating generator and which has a tapered field regulator coupled to the reel motor field regulator so as to provide a non-linear control voltage simulating the torque characteristic of the reel drive with reel diameter. The first roll stand motor 15 has its field excited by a motor regulating generator 58 in accordance with the setting of a speed regulator 63 and the motor current (measured across shunt 57). The speed is automatically controlled in accordance with the output of a master generator 25 by supplying the armature from a main generator 21, the excitation of which is part derived from the master generator and part from a regulating generator 50. The excitation of the regulating generator is dependent upon the master generator, the output of a tachometer generator 29 and a speed compounding component derived from shunt 57. The second, and any subsequent, roll stand motor 16 has its field similarly excited from a motor regulating generator 86. The speed of the motor and the tension in the strip are automatically controlled by supplying the armature from a main generator 22, again excited from the master generator 25 and from a regulating generator 76. The excitation of this regulating generator is dependent upon the master generator, the output of a tachometer generator 69, the motor current (measured by shunt 81), the tension in the strip (controlled by a jockey pulley and bell-crank 93 varying a field regulator 99) and a taper tension component derived from generators 101, 104. The output of generator 104 depends upon the armature voltage of motor 16 whilst that of generator 101 is set at a predetermined value. Hence if the speed of motor 16 is reduced, the voltage of generator 101 exceeds that of generator 104 and a current is passed through one of the field windings of the regulating generator 76 so as to tend to further reduce the speed of motor 16 to reduce the strip tension when the mill is being slowed down. The reel motor 17 has its field excitation controlled by a regulator 115 according to the diameter of the coil, whilst the armature is supplied from a main generator 23, the excitation of which depends on the speed of motor 16 (measured by an auxiliary pilot generator 68) and on an inertia compensating component derived via a regulating generator 122 from bridge 132 and generator 135. The magnitude of this component depends upon the excitation of generator 135 (proportional to the speed of motor 17) and the polarity depends upon whether the master generator raise speed " switch 47 or the " lower speed switch 48 is operated. The output of the inertia compensating generator 135 is, however, reduced at small coil diameters by a tapered field regulator 138 coupled to the coil diameter regulator 115. Specification 649,168 is referred to.