Question

Two wattmeter method one of which reading zero.what is p.f

Answer 1

tan θ = 1.732 (W1-W2)/(W1+W2).

So tan θ = 1.732 (0.5-0)/(0.5+0).

So tan θ = 1.732.

so θ = 60.

cos 60 = 0.5.

hence the power factor will be 0.5

Answer 2

er Method can be employed to measure the power in a 3 phase, three wire star or delta connected the balanced or unbalanced load. In Two wattmeter method the current coils of the wattmeter are connected with any two lines, say R and Y and the potential coil of each wattmeter is joined on the same line, the third line i.e. B as shown below in figure (A).


The total instantaneous power absorbed by the three loads Z1, Z2 and Z3, are equal to the sum of the powers measured by the Two wattmeters, W1 and W2.