hi guys, ive just joined the froum so helpfully you dont mind helping me. im totally lost with this question a 3.3kw single-phase induction motor. The power factor is 0.8 lagging Determine: A)Current drawn from the 230V supply. B)The output power if the overall motor efficiency is 85% C)The active and reactive components of the input current. D) The apparent power and reactive power consumed.
A) current drawn =power/voltage=3300/230=14.35 amps B) input power is Vrms*Irms*cosφ , where cosφ is the power factor=0.8 thus input power Pin=230*14.35*0.8=2640.4 watts the efficiency is 85% thus the motor outputs 85% of its input power so output power Pout=Pin*85%=2640.4*85/100=2244.34 watts C) i am not sure what do you want D) apparent power S=Vrms*Irms=230*14.35=3300 VA reactive power Q=Vrms*Irms*sinφ φ=arccos(0.8)=36.86 degrees therefore Q=230*14.35*sin(36.86)=1979.84 VAR
thats great mike. very much apreciated. just ne lastquestion. where abouts did the 36.86 degress come from?