Switchboards for power, light and railway service, direct and alternating current, high and low tension . are generally good enough insulatorsto hold the circuit connections without further insula-tion, providing they are dry, but in damp weather theirinsulating qualities cannot be depended upon. On thisaccount, for voltages over 500 the switch, circuit breakerand instrument terminals should be insulated from theboard by means of sheet mica washers and tubes, asshown at g k and j in Fig. 29. In Fig. 29 the arrangement of the bus bars and otherconductors on the back of the board is such that th
Switchboards for power, light and railway service, direct and alternating current, high and low tension . are generally good enough insulatorsto hold the circuit connections without further insula-tion, providing they are dry, but in damp weather theirinsulating qualities cannot be depended upon. On thisaccount, for voltages over 500 the switch, circuit breakerand instrument terminals should be insulated from theboard by means of sheet mica washers and tubes, asshown at g k and j in Fig. 29. In Fig. 29 the arrangement of the bus bars and otherconductors on the back of the board is such that theycan be securely held by means of the bolts that form theconnections wnth the various switches, circuit breakersand other apparatus. There are very few cases in whichit is not possible to obtain the necessary support in thisway; when, however, this method will not give all thestiffness necessary to prevent the bars from coming incontact with each other by vibrations, or otherwise, theymust be additionally supported by means of attachmentswith the marble slabs or the supporting frame of thelatter. 75. Designs forholding- barsto framing. mmm. 3 ^ ?:;|) American Machinist Figure Holding conducting bars. In Figs. 32 and 33 a design is shown for holding theconducting bars from the framing. The first one of thesefigures is an elevation, showing a section through the con-ductor H, which is in a horizontal position, and thesecond figure is a plan. In both these figures the con-ductor is marked H and C represents the marble slab. Theconductor H must be insulated from the clamps B and F,and from the bolts g, so that there may be no electricalconnection between it and C or A. Since the object of theinsulation is to separate, electrically, H from C and itssupporting frame A it follow^s that if 5 is insulated fromthe bolt h, and from A, the insulation between H and Bneed not be provided; that is, insulation at one point be-tween H and A is just as good as at another. The con-structio
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1906
