Electrical Engineering Answers

A balanced-Y load is in parallel with a balanced-D-connected capacitor bank.

The Y load has an impedance ZY ¼ ð3 þ j4Þ W per phase, and its neutral is

grounded through an inductive reactance Xn ¼ 2 W. The capacitor bank has

a reactance Xc ¼ 30 W per phase. Draw the sequence networks for this load

and calculate the load-sequence impedances.

Calculate the sequence components of the following balanced line-to- neutral voltages with abc sequence: (25p) 13= Van 1 LV (277/0° = 277/–120 277=120 volts

The synchronous generator in Figure 7.3 is operating at rated MVA, 0.95 p.f.

lagging and at 5% above rated voltage when a bolted three-phase short cir-

cuit occurs at bus 1. Calculate the per-unit values of (a) subtransient fault

current; (b) subtransient generator and motor currents, neglecting prefault current; and (c) subtransient generator and motor currents including prefault

current.

A 500-MVA 20-kV, 60-Hz synchronous generator with reactances Xá = 0.15, Xá = 0.24, Xd 1.1 per unit and time constants T'a = 0.035, T'a = 2.0, TA = 0.20s is connected to a circuit breaker. The generator is operating at 5% above rated voltage and at no-load when a bolted three-phase short circuit occurs on the load side of the breaker. The breaker interrupts the fault 3 cycles after fault inception. Determine (a) the sub-transient fault current in per-unit and kA rms; (b) maximum dc offset as a function of time; and (c) rms asymmetrical fault current, which the breaker interrupts, assuming maximum dc offset.

design a MOD 60 counter

A factory has an operating load of 40kw and a power factor of 0.45 lagging the factory is supplied from a 3 phase 400v supply

calculate the load current of the factory

calculate the KVAr of the factory at 0.45 power factor lagging

the factory operators are required to improve the power factor to 0.9 lagging calculate the KVAr of the capacitor for this operation

calculate the load current drawn by the factory after the power factor correction has been done

The ratings of the various components of a 3-bus system are listed below:

GENERATOR 1: 50 MVA, 13.8kV, X"= 0.15 p.u. ;

GENERATOR 2: 40 MVA, 13.2kV, X" = 0.20 p.u.

GENERATOR 3: 30 MVA, 11kV, X" = 0.25 p.u.

 TRANSFORMER 1: 45 MVA, 11kV, Delta/110 kV Wye, X=0.1 p.u. ; 

TRANSFORMER 2: 25 MVA, 12.5 kV, Delta /115 kV Wye, X = 0.15 p.u.

TRANSFORMER 3: 40 MVA, 12.5kV, Delta / 115 kV Wye, X = 0.1p.u.

The line impedances are shown in the figure. Draw the reactance diagram based on 50 MVA and 13.8 kV as base quantities in Generator 1. Note: Show a complete solution.

Using the supermesh approach, find the current through each element of the

network below.

1.  An activated sludge system has a flow of 4000 m³/day with X = 4000 mg/L and S₀ = 300 mg/L. From pilot plant work the kinetic constants are Y =0.5, μˆ =3 d−1, K_S =200 mg/L. We need to design an aeration system that will remove 90% of the BOD5. Specifically, we need to know (a) the volume of the aeration tank; (b) the sludge age; (c) the amount of waste activated sludge.

What is the approximate velocity resolution that can be provided by a 1-GHz air-search radar in which the antenna with a 5-deg azimuth beamwidth scans at 15 rpm in azimuth? Assume coherent integration over the beam dwell time.