Concatenated induction motors for rolling mill drive

William Oschmann
1914 Proceedings of the American Institute of Electrical Engineers  
The paper descrihes a six-speed concatenated induct ion motor set For driving the iinishing rolls of a 12-stand continuous mill. Analysis of the conditions in this mill showed that the use of a low-])rcssurc turbine would lead to the waste of a large amount of exhaust steam and that the alternating-current turbine plant which was in operation had ample reserve capacity for driving the mill. The large number of speeds required suggested the use of a direct-current motor, but as this required a
more » ... tor-genci'ator set it was found to be more expensive thcin the concateti-'Λίνά motor. An induction motor operating with a speed regulat ing set was also considered but its disadvantages lay in the fact that a commutating motor or synchronous converter would be required, the performance of which at the frequency employed being questionable. The concatenated set installed consists of a double-wound main motor and single-wound secondary motor, both Stators mounted on a common bed-plate and both rotors on a common shaft. The larger motor has both a 14-and Ιϋl)ole stator winding and the secondary motor has its winding arranged for four-and eight-pole connections. The control sys tem is described in d'^tail; its operation is very simple, so that no regular attendant is needed. The motor has six deiinite speeds and two additional resistance speeds, and while the con trol is somewhat complicated it has been made so nearly fool proof as to make a S]:)ccial attendant unnecessary. As a result of the year's operation there have been but three interruptions, the total loss of time due to which has been 68 minutes. T HE USE of a six-speed concatenated induction motor for rolling mill work is of more than passing significance at this time, and a disctission of the various factors which de termined the selection of this type of drive, and the results ob tained, will no doubt be of interest. This motor is used to drive the finishing rolls of a twelve-stand continuous mill. The output of the mill consists of round steel rods ranging from 23/64 to IJ in. (9.1 mm. to 38 mm.) in diameter, also smaü flats, squares and special sections. The former general arrangement of this mill is shown by Fig. 1 . The two heating furnaces are of the continuous type, the billets being conveyed from the furnaces at A to the roughing rolls of the continuous mill at ^, by a chain-driven roUer conveyer. 1027
doi:10.1109/paiee.1914.6660963 fatcat:zkzidir6izfj5dpyrp74dkug3i