Arrangement of Connections. 



113 



tH 



The current branches off to the two shunts, a portion going from 8 14 in the apparatus, the 

 other part passing by the shunt switch into the current regulator; at the contact stud on which 

 Switch Contact II rests the two branches re-unite and from this the whole current flows to the negative 

 pole. In other words, a portion of the potential prevailing at the ends of the resistances 15 and 17 

 (which prevails at 14 and 17) is removed and conducted to this part of the apparatus. Potential 

 Distribution. -- The unshunted current is shown in the illustration by thick lines, and the shunted by 

 thinner lines. The farther apart the Switch Contacts are removed, the lower the tension existing in 

 the apparatus, and the weaker, therefore, the current flowing through the apparatus. As a rule 

 Switch Contact I is placed on the greatest resistance value to the right and Switch Contact II on 

 the lowest to the left, the latter being turned forward until the pressure desired at the apparatus 

 (and therefore the current density) is attained. If Switch Contact II is near the left hand end contact, 

 and if it be desired to increase the current slightly, it is better to move Switch Contact I back than 

 to move No. II forward. Even when this method of connections is adopted it is thus possible to 

 obtain fine regulation with one Switch Contact and coarse with the other. 



If it be desired to feed with current an apparatus which works with an interrupted current 

 (e. g. an induction coil with platinum interrupter or an Ampere table), it may be desirable that at 

 the moment of making the circuit not too high a pressure prevails so as not to burn the contacts 

 by the spark at break. In such cases, when large currents are being used, Switch Contact II should 

 be left in the region of the smaller resistances, while Switch Contact I should be turned backwards. 

 The pressure at the apparatus at the time when no current is being taken off, is to the working 

 voltage as the resistance values placed alongside the contacts on which the Switch Lever rests are 

 to each other. 



A regulation of the current to an extraordinarily fine degree (e. g., in electrolytic operations) 

 is obtained when the apparatus to be connected up is not joined directly to the plug contact pro- 

 vided for the purpose, but a regulating Sliding Rheostat of 2 ohms resistance (No. 50,523, p. 127 

 of this list) put in series with this apparatus. With this sliding rheostat it is possible to regulate 

 the current in stages of about 1 5ll ampere. The smallest current which it is possible to take from 

 the main is nearly ] 5M ampere. Of course if it is desired to measure such low current strengths, 

 a special ammeter must be used, as the ammeter of the switchboard only admits of reading to 

 1 , ampere: instruments with two ranges must therefore be ordered in this case. 



In order to charge the 6-cell battery of 3 amperes charging current previously mentioned, 

 with Type A and 110 volts pressure. Switch Contact II should be placed on 12 ohms and Switch 

 Contact I on 36 ohms, the current in the apparatus being then 3 amperes, the shunted current 

 1 ampere, and the total current consumption 4 amperes. 



With Type B and 220 volts 

 working pressure Switch Contact II 

 must be on 6 ohms and Switch 

 Contact I on 48 ohms; the current 

 in the apparatus being 3 amperes 

 and the shunted current 2 amperes, 

 and the total current consumption 

 5 amperes. Let the voltage of the 

 supply current be S,, the position 

 of the Switch Contacts Kj and K 2 

 respectively, the resistance of the 

 apparatus A, the pressure to the 

 apparatus S 2 , the current in the 

 portion of resistance between 

 Switch Contact I and Switch 

 Contact II Jj. the current density 

 in the apparatus J 2 , the current 

 in the part of the resistance be- 

 tween Contact II and J 3 = J\ 

 J 2 ; then 



AS, K. ; 



S* = 



S, (A 



Overall Dimensions of Switchboards Types A, B and C. 



K, (A + K.) - K., s 



S.K, 



K, (A + K.) - Ev 



A Si 



K/ \ i ~rr \ "tr 3 

 1 V-^ ~T~ -*^2/ -**-2 



Cl 5168, 5169. 



