i) Assumptions:-

a) The 3-ø system consider here is a load, which is delta connected.

b) The phase sequence is R→Y→B.

c) It is balanced load.

d) The p.f. of each phase is logging.

ii) Connection:-

iii) Proof:-

Reading of wattmeter W1

$W_1=V_{RB}I_{RL} \cos(\angle between V_{RB} \& I_{RL})=V_LI_L \cos(30^0-\emptyset_{ph})$

Reading diagram W2

$W_1=V_{YB}I_{YL} \cos(\angle between V_{YB} \& I_{YL})=V_LI_L \cos(30^0+\emptyset_{ph})$

$(W_1+W_2)=V_LI_L\{\cos(30^0-\emptyset_{ph})+\cos(30^0+\emptyset_{ph})\} \\ =V_LI_L\{2\cos30^0.\cos\emptyset_{ph}\} \\ =V_LI_L\bigg\{2\times\dfrac{\sqrt3}{2}\cos\emptyset_{ph}\bigg\} \\ =\sqrt3V_LI_L \cos \emptyset_{ph} \\ =\text{Total power consumed by the 3-}\emptyset \text{load phasor diagram on}P_011$