ELECTRICAL DRYING OF TELEPHONE CABLE 



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resistance between wires is low in an undried cable, particularly when 

 moisture is leaving the cable during the drying operation. The choice 

 of direct current not only eliminated the danger of breakdown between 

 conductors (all conductors are grouped in parallel) but simplified the 

 preparation and clamping of the cable for drying. Direct current also 

 makes it possible readily to obtain practically any starting voltage 

 between the maximum and minimum range of the equipment, a require- 

 ment necessitated by the great variety of cable lengths. 



The electric drying installation at Kearny consists of a motor gen- 

 erator set for supplying the direct current for heating. Fig. 1, control 



Fig. 1 — Power supply set showing two generators for furnishing heating current. 



equipment for starting and regulating the motor generator set, Fig. 2, 

 and dome type dryers for holding the cable and its core truck under 

 a vacuum of }/2 inch to 1 inch of mercury back pressure during the 

 heating and evacuation period, Fig. 3. A central control panel is 

 located at the dryers on which is mounted apparatus for limiting the 

 heating period to a predetermined amount, as well as visual instru- 

 ments for indicating information for the operator's use in properly 

 running the drying process. 



All cables are dried at the same starting current density per unit 

 of cross-section of the copper wire. With this as a starting point the 



