ALTBRNATINCWVRRSNT CIRCUITS 



49 



ti is called the energy component of the current, because this 

 component multiplied by the voltage gives the circuit power. 



The component z' 2 is in quadrature with the voltage and can 

 contribute no power therefore. z' 2 is called the quadrature or 

 wattless component of the current. 



Energy Current ' l. 



Quadrature 

 Current 



FIG. 46. Energy and quadrature currents. 



If this load is being supplied over a transmission line, the line 

 loss is proportional to 



PR = (i! + iJ)R = i^R + iJR 



where R is the transmission line resistance. 



It will be observed that the quadrature component produces 

 line loss, yet contributes no power to the load. Therefore, it 

 is ordinarily desirable to make z' 2 as small as possible or, in other 

 words, have the system operate at a high power-factor. For 

 example, when 6 = 45, P.F. = 0.707, the energy and quadrature 

 currents are equal. Therefore, the quadrature current con- 

 tributes as much to the line loss as the energy current does, but 

 it contributes nothing to the power supplied to the load. 



</>/'. A transmission line. Fig. 47 (a), supplies ">() kw. at 220 volts, 

 single-phase, to a load having a power-factor of (Mil), lagging current. Each 



o.oz n 





Volt* 



47. Energy and quadrature -^mi^ion lin.-. 



wire haa a resist '>-j,,hm. l-'md: (m The energy ciirreir 



Hire current. () The line loss due to the energy current. (< 



> c cjuadrnture current. (> i The total | m r loss. (/) The lino 

 low which wouk 'he load po\\ er-factor were unity. 



