Hello, im new to this forum and have used it in the past for studying, im wondering if anyone could give me help on a question Ive been trying to figure out involving calculating power factor of an RL Circuit when the frequency has changed.
A 240v 50hz appliance is rated at 2Kw and has a lag PF of 0.7
Calculate the new PF at 60hz.
Heres what Ive done so far:
Sketched a Power triangle True power (P) = 2000w
Apparent (S)= 2860VA (S= P/PF)
Calculating I
Vs=240v
Apparent (S)=Vs x I
I=S/Vs = 11.92A
Finding Q (Reactive Comp.) by Pythagoras.
b= root (c2-a2)
Q= 2044va
Finding Inductive Reactance
Xl=Vs2/Q = 240squared/2044
Xl=28.18
Total Cct Impedance
Z= Vs/I = 240/11.92= 20.13Ω
Using XL = 2piFL
Transpose to find L
L= 632mH
Cos θ = PF=0.7
Cos-1PF= θ
Θ=45.57degrees
I have tried changing the Freq in the equation 2piFL =Xl giving two new values of Xl but I cant seem to be able to construct a new power triangle with just this info. Having got to this point I am not sure what my next step is any pointers would be of a great help.
Cheers
Rubberfrog
A 240v 50hz appliance is rated at 2Kw and has a lag PF of 0.7
Calculate the new PF at 60hz.
Heres what Ive done so far:
Sketched a Power triangle True power (P) = 2000w
Apparent (S)= 2860VA (S= P/PF)
Calculating I
Vs=240v
Apparent (S)=Vs x I
I=S/Vs = 11.92A
Finding Q (Reactive Comp.) by Pythagoras.
b= root (c2-a2)
Q= 2044va
Finding Inductive Reactance
Xl=Vs2/Q = 240squared/2044
Xl=28.18
Total Cct Impedance
Z= Vs/I = 240/11.92= 20.13Ω
Using XL = 2piFL
Transpose to find L
L= 632mH
Cos θ = PF=0.7
Cos-1PF= θ
Θ=45.57degrees
I have tried changing the Freq in the equation 2piFL =Xl giving two new values of Xl but I cant seem to be able to construct a new power triangle with just this info. Having got to this point I am not sure what my next step is any pointers would be of a great help.
Cheers
Rubberfrog