ELECTROFORMED CONDUCTOR FOR TELEPHONE DROP WIRE 1121 



480 volts ac and having at least 105-kva capacity according to NEMA 

 standards. Each regulator is able to buck or boost line voltage by 20 per 

 cent at maximum rectifier load. 



The rectifiers used for converting three-phase, 60-cycle, 480-volt ac 

 power to low voltage dc are all of the copper-oxide ' 'dry-disc " type. A 

 detailed investigation of various sources of dc power was made before 

 this type of converting equipment was purchased. Because of the simi- 

 larity between the continuous copper plating of wire and the continuous 

 tin-plating of sheet steel, a tour of several steel plants which plated strip 

 steel in a continuous process was made. Here were observed some of the 

 best and some of the poorer installations of electrical converting equip- 

 ment, including motor-generator sets, copper-oxide rectifiers and sele- 

 nium rectifiers. This survey terminated in a decision to use totally 

 enclosed, air cooled copper-oxide rectifiers, in which the enclosed air is 

 recirculated past air-to-water heat exchangers for cooling purposes. This 

 decision was based on a desire for low maintenance costs, efficiency, 

 compactness of installation and flexibility. Choice of copper oxide over 

 selenium rested on the fact that copper oxide rectifiers are less costly 

 and better suited for low voltage output (less than 6 volts). 



The actual design of the rectifiers was arrived at after a series of con- 

 ferences between Western's engineers and those of the manufacturers. 

 Accessibility of all parts for inspection and maintenance purposes, ade- 

 quate protection of components through control circuits, limited oc- 

 cupancy of floor space and low cost were design criteria. These features 

 are nicely combined in the final design and the manufacturer standard- 

 ized the rectifier for sale to other purchasers. 



Each rectifier is of the completely enclosed, air recirculating type. It 

 is equipped with its own heat exchanger and is gasketed to minimize air 

 leakage. The air-to-water heat exchanger is of a type expecially designed 

 for use with well water containing some fine sand. It features ease of 

 cleaning and is a type suitable to these conditions. The fins and tubes 

 are of copper and water connections are external to the rectifier housing. 



All other components are readily accessible through gasketed doors in 

 the housing. One or two fans, as required, circulate the air within the 

 rectifier housing to transfer the heat generated in the rectifier cells and 

 in the transformers to the water cooled heat exchanger. As protection 

 both to equipment and to personnel, a rectifier can be automatically 

 tripped off the line for any of the following reasons: Electrical overload 

 and short circuit, dc over-voltage, failure of air circulation, overload of 

 fan motor, water failure, momentary power interruption, over-tempera- 

 ture of the air, and by opening any of the doors on the rectifier. 



