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XVIII. Note on the Voltage Ratios of an Inverted Rotary 

 Converter. By W. C. Clinton, JB.Sc, AM.Inst.E.E. ; 



Demonstrator in the Fender Electrical Laboratory , 

 University College, London *. 



IF a separately excited rotary converter be driven at a 

 constant speed with the rings and brushes on open circuit, 

 the ratios o£ the maximum alternating E.M.F. between the 

 rings to the E.M.F. over the brushes is given by a well- 

 known expression on the assumption of a sinusoid distribu- 

 tion o£ the air-gap magnetic flux over the surface of the 

 armature. 



Putting Ea and E c for the alternating and continuous 

 E.M.F. 's respectively, and n for the number of rings, then 



E c n 



where — is the angular width in degrees of phase between 



the contacts for two successive rings. 



If, however, the converter be driven by current supplied 

 to either side, the other side being on open circuit, then a 

 correction on the above value becomes necessary owing to 

 ohmic drop in the armature conductors. 



Let direct current be supplied to the commutator, the rings 

 being on open circuit. Let the resistance of a single path 



through the armature from brush to brush be E, and let the 

 current flowing in that path be C, Then the ohmic drop 

 from brush to brush is Cli. 



* Communicated by the Physical Society : read March 24, 1905. 



