I have been trying to solve homework questions on three phase systems but I am got stuck in two questions while solving solving them.
Three similar impedances are connected in star across 2000V, 50Hz three phase supply. Power absorbed is 300KW. Current taken is 100A lagging. Find the values of circuit parameters in each phase.
While Solving this, I calculated : V_ph =2000/√3=1154.7V and the impedence to be: Z=Vph/100=11.54 ohms.
The power factor is:2000/3XVphXIph which comes out to be 0.28.
My question is how can i caluculate the power for each impedence.As far as I know ,I only know equation for total power
A three phase 400V motor has an output of 20HP with efficiency of 90% and at a power factor of 0.8. Determine the reading on each of the two wattmeters connected to measure the input. Also find the line current.
So input Power is 90% of 20 that is 18 Watts
So I presume W1+W2=18 watts
My book gives the formula: tan(θ)=√3(w2-w1/w2+w1) or tan(θ)=-√3(w2-w1/w2+w1) where w1 and w2 are wattmeter readings in the wattmeter. My question is how do i identify which equation to use.
Can anyone please help me with these doubts and also tell me what I am doing wrong.
input power is 100HP=74.57kW.