Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . he lowercontact up or down, taking care that it is kept parallelwith the upper contact, so that when they are closed,contact will be made across its whole width. If thisadjustment is not properly made there will be destruc-tive sparking on a small portion of the contact surfaces. 4. All connections must be perfectly secure. 5. The check nuts N must be tight. 6. The carbons in the tubes L must be whole. Thesecarbons form a permanent shunt of high resistancearound the regulator magnet M, and if brok
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . he lowercontact up or down, taking care that it is kept parallelwith the upper contact, so that when they are closed,contact will be made across its whole width. If thisadjustment is not properly made there will be destruc-tive sparking on a small portion of the contact surfaces. 4. All connections must be perfectly secure. 5. The check nuts N must be tight. 6. The carbons in the tubes L must be whole. Thesecarbons form a permanent shunt of high resistancearound the regulator magnet M, and if broken willcause destructive sparking at contacts O, burning themand seriously interfering with close regulation of thegenerator. In case a carbon should become broken, 100 ELECTRICITY FOR ENGINEERS temporary repairs may be made by splicing the brokenpieces with a fine copper wire. To keep the action of the controller perfect the con-tacts O should be occasionally cleaned by inserting afolded piece of fine emery cloth and drawing it backand forth. The amount of current generated by each machine. FIGURE 59. depends upon the adjustment of the spring S. If thetension of this spring is increased the current will bediminished; if the tension is diminished, the currentwill be increased. In starting these dynamos when the armature hasreached its proper speed, the short circuiting switch onthe frame should be opened. This method allows the ELECTRICITY FOR ENGINEERS 101 generator to take up its load gradually, and is a veryimportant point in the handling of the machine. Arc Switchboards. Fig. 59 shows a general view ofthe Thomson-Houston plug switchboard. A rear viewof the same board is given in Fig. 60. In a standard panel the number of horizontal rowsof holes equals one more than the number of gener-ators. The vertical holes are always twice the numberof generators. The positive leads of the generators are
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