Αποτελέσματα Αναζήτησης
Machines and transformers have capacity limits and power losses that are independent of cos φ; their ∝ ratings are always given in apparent power. Power Company: Costs apparent power, Revenue ∝ average power. Power in R, L, C. Tellegen’s Theorem. Power Factor Correction.
Identify the components of complex power. Compute complex power given ac voltage and current. Apply the correct sign convention for absorbed and delivered power. Draw power triangles for resistive/inductive and resistive/capacitive loads.
Example single-phase circuit: ^Va sin( R L. a + !t) C. ^Vb sin( b + !t) Instantanteous values (stigmiaÐec timèc) of voltage and current at a network element given by. v(t) = ^V cos(!t) i(t) = ^I cos(!t ') ^V and ^I are the amplitudes (mègisth tim ) of the respective waveforms (kummatomorfèc)
-Explain the magnitude and angular relation between the phase and line voltages in a WYE and DELTA systems.-Calculate real, reactive, and apparent power in single-phase and three-phase circuits.-Define power factor.-Solve power factor correction problems 2
1 Draw the relevant phasor diagrams and waveform diagrams of voltage and current, for pure resistance, inductance and capacitance. Understand and use the concepts of reactance and impedance to analyse simple a.c. series circuits. 3 Derive and use impedance and power triangles.
Power in Single Phase AC Circuits. Let us consider the following circuit. i(t) +. − v(t) V. Load I. θV θI. Let. √. v(t) = Vm sin(ωt + θV ) = 2V sin(ωt + θV ) √. i(t) = Im sin(ωt + θI ) = 2I sin(ωt + θI ) The instantaneous power delivered to the load is. p(t) = v(t)i(t) p(t) = Vm sin(ωt + θV )Im sin(ωt + θI ) VmIm.
Example Calculate the power consumed in a single phase a.c. circuit which is energised by a 240-V, 50-Hz sinusoidal supply, the load being a resistance of value 100 n. Solution. Vs = 240 V;R = 100 n Since the only element in the circuit is the resistor, then. VR = Vs =240 V. From eqn (11.1) current,J= VR. R. and from eqn. (11.2) = 240 = 2.4 A. 100.
