1492 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



furnished by different manufacturers. To appraise properly the qualities 

 of different manufacturers' stacks, the stability of the life characteristics 

 should be considered more important than the initial characteristics. 



There is very little information published by the selenium manufac- 

 turers regarding the life expectancy of their product. Aging appears to 

 be directly related to the individual manufacturing techniques used by 

 each supplier. The life of selenium rectifier stacks seem to decrease as 

 the cell voltage rating is increased. Longer life can be expected if stacks 

 are operated at load currents below the present ratings given in the manu- 

 facturers' literature. 



Selenium rectifier stacks properly designed and conservatively rated 

 can be expected to give satisfactory performance for 10 to 20 years. 

 Careful consideration of the rate and extent of aging must be evaluated 

 so that proper allowance may be made in the circuit design to obtain 

 maximum life expectancy. 



REFERENCES 



E. A. Harty, Characteristics and Applications of Selenium Rectifier Cells, Elec. 

 Eng., Oct., 1943. 



J. H. Hall, Transformer Calculations for Selenium Rectifier Applications, Elec. 

 Eng., Feb., 1946. 



Glen Ramsey, The Selenium Rectifier, Elec. Eng., Dec, 1944. 



J. Gramels, Problems to Consider in Approving Selenium Rectifiers, A.I.E.E. 

 Technical Paper No. 53-215. Also published in Communications and Elec- 

 tronics, Sept., 1953. 



W. F. Bonner, Advanced Developments in Metallic Rectifiers, Electrical Manu- 

 facturing, Oct., 1951. 



I. T. Cataldo, Development of 40-volt Selenium Rectifier Plates, Electrical 

 Manufacturing, May, 1952. 



S. Niciejenski, Selenium Rectifiers, Radio and Television News, Oct., 1952. 



H. K. Henisch, Metal Rectifiers, Oxford, Clarendon Press, 1949. 



E. A. Richards, The Characteristics and Applications of the Selenium Rectifier, 

 J. Inst. Elec. Engrs. (London), 88, Part III, Dec, 1941. 



