[Electric engineering.] . 20-volt dynamo isconnected to the outside wires, and if a larger current isneeded on one side of the battery than on the other, theextra current is supplied from the battery. It is not, how-ever, generally advisable to use a battery in this way formaintaining the balance continuously as the cells becomeunevenly discharged. When batteries are used on three-wire systems, they are usually connected across the outsidelines and a switch provided to connect their middle point withthe neutral, so that they can be used for balancing in caseof necessity. 5(y. Fig. 29 shows a t
[Electric engineering.] . 20-volt dynamo isconnected to the outside wires, and if a larger current isneeded on one side of the battery than on the other, theextra current is supplied from the battery. It is not, how-ever, generally advisable to use a battery in this way formaintaining the balance continuously as the cells becomeunevenly discharged. When batteries are used on three-wire systems, they are usually connected across the outsidelines and a switch provided to connect their middle point withthe neutral, so that they can be used for balancing in caseof necessity. 5(y. Fig. 29 shows a three-wire system fed by a 220-voltdynamo A in conjunction with a motor-dynamo a a. Thismotor-dynamo is sometimes called a balancing set or bal-ancer. The armatures a, a are mounted on the same shaftand connected in series, the mid-point n being connected tothe neutral wire. The fields of these two machines are con-nected across the mains, as shown at//. When one sideof the system is more heavily loaded than the other, the. Fig. 29. machine on the heavily loaded side runs as a dynamo and helps to supply current to that side, while the machine on the lightly loaded side absorbs power and runs as a motor, thus equalizing the load. Take, for example, the special case shown in Fig. 29, where we have 12 lamps on one side and 6 on the other. We will have 18 lamps to be supplied with power from the 220-volt machine A. Allowing 55 watts , • • „ j i 55 X 18 per lamp, this gives 55 X 18 watts and, hence, ———— = 4r| amperes. The current flowing out on F and back § 16 ELECTRIC LIGHTING. 47 on F must, therefore, be 4£ amperes. The upper side ofthe three-wire system requires 6 amperes and the lowerside 3, because we have 12 lamps in parallel in the one caseand 6 in the other. We have, then, 3 amperes coming backthrough the neutral, of which 1^ flows through a, runningit as a motor and generating 1| amperes in a. This\\ amperes is added to the 4|- in line F, thus making the6 re
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