[Electric engineering.] . 7alcarf. Fig. 44. a balanced load, as, for example, a load consisting wholly ofthree-phase motors, one wattmeter may be used to measurethe power, as indicated in Fig. 44. The method of connect-ing the. potential coil/ and the resistances rlf r2, and r3should be noted. Theseresistances are connect-ed as shown in order toobtain an artificial neu-tral point, similar to thecommon connection ofa Y-connected three-phase armature. Thiscombination of resist-ances is sometimescalled a Y resistance,or a Y box. Althoughthe current coil is in oneside of the system only,the instru
[Electric engineering.] . 7alcarf. Fig. 44. a balanced load, as, for example, a load consisting wholly ofthree-phase motors, one wattmeter may be used to measurethe power, as indicated in Fig. 44. The method of connect-ing the. potential coil/ and the resistances rlf r2, and r3should be noted. Theseresistances are connect-ed as shown in order toobtain an artificial neu-tral point, similar to thecommon connection ofa Y-connected three-phase armature. Thiscombination of resist-ances is sometimescalled a Y resistance,or a Y box. Althoughthe current coil is in oneside of the system only,the instrument can becalibrated to read thetotal watts delivered,assuming, of course,that the load is bal-anced /. III.—7. Meter Field po\_flfio r3 r^ra T4 nh. Fig. 45. 92 ELECTRIC TRANSMISSION. 14 106. Fig. 45 shows how to connect a Thomson record-ing wattmeter with its Y resistance so as to measure thepower on a balanced three-phase circuit. The recordingmeters are so calibrated that their reading multipliedby the meter constant, if there is one, gives the total power supplied. Fig. 45shows the connectionswhen the meter is usedon circuits where thepressure is not over500 volts. When thepressure is higher thanthis, small transform-ers t, t, Fig. 46, areused to step down thevoltage for the pres-sure coil of the record-ing wattmeter, and theconnections are asshown in the figure re-ferred to. 107. If the cur-rent in each line of abalanced three-phasesystem is C, the pres-sure between theFlG- 46, lines E, and the power factor of the load/, then the watts delivered will be
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