ARMATURE LAMINATIONS 



29 



the iron-testing room of a rolling mill. The Epstein sample 

 may be seen on the table at the right of the figure. 

 . A testing-room fitted out with a Kichter apparatus which is 

 capable of testing, at one time, four complete sheets measuring 

 1 metre x 2 metres, is shown in Fig. 15. This installation is on 

 the premises of a rolling mill. 



The provision to electrical manufacturers, of punchings com- 

 pletely finished, including the slots, has been undertaken in 

 England by certain firms ; but the largest manufacturers of dynamo- 

 electric machinery do their own punching work. 



The most customary standard size in which sheet steel for 

 armatures is delivered, is in plates measuring 1 metre x 2 metres. 



FIG. 13. Photograph of Epstein Iron Tester. 



Plates of larger dimensions are generally only supplied at higher 

 prices, and a longer time is required for providing them. It has 

 thus become fairly general practice to build up armature cores 

 of larger diameters than 1000 mm., out of segments whose 

 maximum dimensions do not exceed the dimensions of sheets 

 of this standard size. Frucht l suggests that 990 mm. be 

 standardised as the largest diameter of armature in which 

 complete discs shall be employed. 



In Figs. 16 to 21 are drawn, to a scale of 20 : 1, six such normal 

 plates, on which are indicated the outline of armature plates which 

 may serve as instances of standard practice. 



1 Z&itschr. des Vereines Deutscher Ing., 30th May 1903, p. 769 : " Die 

 Herstellung der im Dynamobau gebrauchten Bleche." 



