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Power Factor- Parallel Circuits. Determine R and X given V, I and P V is found from a Voltmeter I is found from an ammeter P is found from a wattmeter. Definitions. G = (1/R) is called conductance B = (1/X) is called sucepatance B L (for an inductor) = (1/j w L) = (-j/ w L)
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Power Factor- Parallel Circuits Determine R and X given V, I and P V is found from a Voltmeter I is found from an ammeter P is found from a wattmeter
Definitions • G = (1/R) is called conductance • B = (1/X) is called sucepatance • BL (for an inductor) = (1/jwL) = (-j/wL) • BC (for a capacitor) = (1/(1/jwC)) = jwC • Y = (1/Z) is called admittance • For a parallel RL circuit: • Y = G - jBL
Example # 2 • Given: • The voltmeter reading is 120 volts • The ammeter reading 15 amps • The wattmeter reading is 900 watts • Determine: • R • jXL
Solution • Solve for q • q = cos-1(P/VI) = cos-1(900/(120x15)) = 60o • Y = (I/V) / -q = (15/120) / -q = 0.125/ -60o • This is in Polar form - and • Y= 0.0625 - j 0.10825 (in Rectangular form) • We now have: • G = 0.0625 S • jBL = -j 0.10825 S
To find R • G = 0.0625 S • But we don’t want G we want R • To find R: • Program your calculator for Complex operations (CPLX) • Press “real” (F2) (0.125/-60o) • Now invert the answer to find R = 16 W
To Find X • B = 0.1082 S • But we don’t want B we want X • To find X: • Program your calculator for Complex operations (CPLX) • Press “imag” (F3) (0.125/-60o) • Now invert the answer to find jXL = j9.237 W