A source supplies power to the following three loads connected in par- allel: (1) a lighting load drawing 10 kW, (2) an induction motor drawing 10 kVA at 0.90 power factor lagging, and (3) a synchronous motor operating at 7.5 kW, 85% efficiency and 0.95 power factor leading. Deter- mine the real, reactive, and apparent power delivered by the source. Also, draw the source power triangle.

A source supplies power to the following three loads connected in par- allel: (1) a lighting load drawing 10 kW, (2) an induction motor drawing 10 kVA at 0.90 power factor lagging, and (3) a synchronous motor operating at 7.5 kW, 85% efficiency and 0.95 power factor leading. Deter- mine the real, reactive, and apparent power delivered by the source. Also, draw the source power triangle.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter2: Fundamentals

Section: Chapter Questions

Problem 2.24P: A source supplies power to the following three loads connected in parallel: (1) a lighting load...

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A source supplies power to the following three loads connected in parallel: (1) a lighting load drawing 10kW. (2) an induction motor drawing 10kVA at 0.90 power factor lagging, and (3) a synchronous motor operating at 10hp,85 effIciency and 0.95 power factor leading (1hp=0.746kW). Determine the real, reactive, and apparent power delivered by the source. Also, draw the source power triangle.
Consider a load impedance of Z=jwL connected to a voltage and V let the current drawn be I. (a) Develop an expression for the reactive power Q in terms of ,L, and I, from complex power considerations. (b) Let the instantaneous current be i(t)=2Icos(t+). Obtain an expression for the instantaneous power p(t) into L, and then express it in terms of Q. (c) Comment on the average real power P supplied to the inductor and the instantaneous power supplied.
Is the power factor in Question 6 a leading or lagging power factor? Explain your answer.
The real power delivered by a source to two impedances, Z1=4+j5 and Z2=10 connected in parallel, is 1000 W. Determine (a) the real power absorbed by each of the impedances and (b) the source current.
Under balanced operating conditions, consider the three-phase complex power delivered by the three-phase source to the three-phase load. Match the following expressions, those on the left to those on the right. (i) Realpower, P3 (a) (3VLLIL)VA (ii) Reactive power, Q3 (b) (3VLLILsin)var (iii) Total apparent power, S3 (c) (3VLLILcos)W (iv) Complex power, S3 (d) P3+jQ3 Note that VLL is the rms line-to-line voltage, IL is the rms line current, and is the power-factor angle.
Let a series RLC network be connected to a source voltage V, drawing a current I. (a) In terms of the load impedance Z=ZZ, find expressions for P and Q, from complex power considerations. (b) Express p(t) in terms of P and Q, by choosing i(t)=2Icost. (c) For the case of Z=R+jL+1/jC, interpret the result of part (b) in terms of P,QL, and Qc. In particular, if 2LC=1, when the inductive and capacitive reactances cancel, comment on what happens.
An industrial load consisting of a bank of induction motors consumes 50 kW at a power factor of 0.8 lagging from a 220-V,60-Hz, single-phase source. By placing a bank of capacitors in parallel with the load, the resultant power factor is to be raised to 0.95 lagging. Find the net capacitance of the capacitor bank in F that is required.
A single-phase, 120V(rms),60Hz source supplies power to a series R-L circuit consisting of R=10 and L=40mH. (a) Determine the power factor of the circuit and state whether it is lagging or leading. (b) Determine the real and reactive power absorbed by the load. (c) Calculate the peak magnetic energy Wint stored in the inductor by using the expression Wint=L(Irms)2 and check whether the reactive power Q=Wint is satisfied. (Note: The instantaneous magnetic energy storage fluctuates between zero and the peak energy. This energy must be sent twice each cycle to the load from the source by means of reactive power flows.)
The voltage v(t)=359.3cos(t)volts is applied to a load consisting of a 10 resistor in parallel with a capacitive reactance XC=25. Calculate (a) the instantaneous power absorbed by the resistor, (b) the instantaneous power absorbed by the capacitor. (c) the real power absorbed by the resistor, (d) the reactive power delivered by the capacitor, and (e) the load power factor.
In an energy transmission system with a power value of 100 MVA and a power coefficient of 0.8 reverse (inductive), the generator in a hydroelectric power plant was operated as an over-excited synchronous motor for grid power compensation and was connected to this system as a capacitive load of approximately 40 MVAR. Show the active, reactive and apparent powers on the phasor diagram (power triangle) and calculate the new power factor after the synchronous capacitor is connected.
An industrial firm has two electrical loads connected in parallel across the power source. Power is supplied to the firm at 4000 Vrms. One load is 30 kW of heating use (resistive), and the other load is a set of motors that together operate as a load at 0.6 lagging power factor and at an apparent power of 150 kVA. a) Calculate the complex powerSmused by the motors.
An industrial plant consisting primarily of induction motor loads absorbs 500 kW at 0.6 power factor lagging. (a) Compute the required kVA rating of a shunt capacitor to improve the power factor to 0.9 lagging. (b) Calculate the resulting power factor if a synchronous motor rated at 375 kW with 90% efficiency operating at rated load and at unity power factor is added to the plant instead of the capacitor. Assume constant voltage.