a) In a mono-phase AC network with the supply voltage U [V], we want to measure the

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a) In a mono-phase AC network with the supply voltage U [V], we want to measure the power drawn by a load of the power factor pf which draws a current of I [A]. The W-meter used for this purpose has the ranges: "Unw=20, Inw=1/4". Determine appropriate specs for additional components to be used and draw the whole measuring circuit. According to your circuit, calculate the pf, in case the W-meter pointer deflects by 1/10th of full scale (Qw=Qwmaw/10).

b) In a 3-phase balanced system with inductive load, the voltage circuit of a W-meter is connected between the phases T-R (not R-T !) (Uw=Uru) and the current of phase S is flowing through the current coil of the W-meter (Iw=Is). By drawing the phasor diagram obtain the total reactive power drawn by the load in terms of the value Pw the W-meter reads.