Electrical Engineering Answers

Use linearity and the assumption that 𝑉0=1 𝑉, find the actual value of 𝑉0

Two power stations, A and B, are synchronized at 88 kV. They are interconnected by a transmission line with an inductive reactance of 5.7 Ω and resistance of 1.3 Ω. The voltage of power station A is advanced with an angle of 7.8 degrees with respect to the voltage of power station B. The loading of power station B has a real power of 312.31 MW. The respective loads of the two power stations are as follows:

Power station A: 700 MVA at a power factor of 0.819 lagging.

Power station B: The reactive power consumed by the load is 412 Mvar.

Use the complex power method to calculate the interconnector current  (I_ij) in kA in polar form

In a three-phase, four-wire system, the currents in lines A, B and C under abnormal conditions of loading were as follows:

 I_a = 100∠ 30°  A;            I_b=50∠ 300° A ;    and       I_c=30∠ 180 ^° A.

 Determine the zero-phase sequence current  (I_ao) in line A in polar form.  

An unbalanced, three-phase, three-wire, star-connected load is supplied from a balanced three-phase source at 380 V,50 Hz. The phase sequence impedances of the load are the following:  

Z_a =17.5 ∠ - 34.2°Ω ;               Z_b=13.9 ∠ 68.15° Ω  ;               Z_c =14.2 ∠ - 49.7° Ω 

Take E_ab as a reference, with a phase sequence of ACB.

Use Millman’s theorem and determine the phase voltage (I_c) of the load in polar form.

raw the filter of the equation x(t) given below. Design the filter using a Butterworth filter. Verify the filter design and adjust n as needed. - Test the filter and explain what you get? x(t) = 3 sin(51130t)+ 15cos(61250t)

A 208 V, 60 Hz, 4 poles, star connected SCIM gave the following test results

N.L. test: 450W, 208V, 1.562A, B.R. Test : 59.4W, 27V, 2.77A

The stator winding resistance between any two terminals=2.4Ω.

a. Compute the equivalent circuit parameters of the motor.

b. Determine the shaft torque and the efficiency of the motor if it is running at its rated speed of

1710rpm.

A 3 phase, 400 V, 50 Hz, 4 pole, star connected SCIM has the following per phase constants

in ohms referred to stator:

r1= 0.15, x1=0.45, x2=0.45, Xm= 28.5

Rotational losses= 400W.

Compute stator current, rotor speed, output torque and efficiency when the motor is operated at

rated voltage and frequency at 4% slip.

A 10kW, 400 V, 4pole, delta connected SCIM gave the following test results,

N.L. test: 250W, 400V, 8A, B.R. Test : 1350W, 90V, 35A ,

The stator winding resistance/phase is 0.72 ohms/phase. Calculate rotational losses and the

equivalent circuit parameters of the motor.

Some foreign countries, particularly those in the early stages of industrial development, are known to illegally copy product designs and technologies that originated from developed countries. What are the best ways for small businesses to protect their technical knowhow in foreign countries?

A company decides to offer an average annual raise of 8%, although the current inflation rate is 10%. Each engineering manager decides on the best way to distribute the salary increases to his or her staff. However, if everyone gets an increase of 8%, there will be no differentiation between strong and weak performers for the previous year. What should you do as an engineering manager?