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B. 1V, 1 kΩ D. 1mV, 10 Ω D. Symmetrical Components916. REE Board Exam October 1998

A. 10 + j4 C. -8 – j4B. 8 – j6 D. 12 – j6

921. REE Board Exam October 1997

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If the loads of a wye-connected transformer are:Ia = 10 cis (-30°)Ib = 12 cis 215°Ic = 15 c is 82°

What is the phase b positive sequence component? A. 13.4 cis (-32.2°) C. 12.27 cis 208.4°B. 10.2 cis 240° D. 12.27 cis (-31.6°)

917. REE Board Exam March 1998, September 2001The three unbalanced currents are:

Ia = 10 cis (-30°)Ib = 0Ic = 10 cis 150°

Find the negative sequence current of phase a. A. 8.66 cis 30° C. -5.77B. 5.77 cis (-60°) D. 5.77

918. EE Board Exam October 1984Given the following currents:

Ia = 60 + j0 AIb = -36 – j48 AIc = -48 + j36 A

Solve for the negative sequence component Ia. A. 8.641 – j1.543 C. 9.751 – j1.464B. 9.436 + j1.346 D. 8.354 + j1.034

919. REE Board Exam October 1998The three unbalanced currents are:

Ia = 10 cis (-30°)Ib = 0Ic = 10 cis 150°

Find the zero sequence current. A. 3.33 cis 30° C. 5.77B. 0 D. 3.33

920. EE Board Exam October 1984Given the following currents:

Ia = 60 + j0 AIb = -36 – j48 AIc = -48 + j36 A

Solve for the zero component of Ia.

The sequence currents of phase a current are as follows:Zero sequence current =Positive sequence current =Negative sequence current =

Determine the phase a current. A. C.B. D.

922. REE Board Exam October 1998The sequence components of phase a current are:

Zero sequence current = 0.47 + j1.49Positive sequence current = 18.4 cis (-31.6°)Negative sequence current = 3.23 cis 168.2°

Determine the phase b current. A. 18 cis 215° C. 19 cis 220°B. 15 cis 240° D. 20 cis 225°

923. REE Board Exam March 1998The sequence components of phase a current are:

Zero sequence current = 0.47 + j1.49Positive sequence current = 18.4 cis (-31.6°)Negative sequence current = 3.23 cis 168.2°

Determine the phase c current.

A. 17.5 cis 91° C. 22.5 cis 82°B. 18 cis 215° D. 15 cis 100°

924. EE Board Exam April 1992Determine the symmetrical components of the line current in line ‘athe in-phase impedance of its delta connected load connected across lines‘ca’ is removed. The delta load with impedance ofohms per phase issupplied from a 220 volts, 60 cycle, 3-phase source. Assume a phasesequence of a-b-c. A. Ia1 = 11 A, Ia2 = 11 A, Ia0 = 0 AB. Ia1 = 7.33 A, Ia2 = 7.33 A, Ia0 = 7.33 AC. Ia1 = 22 A, Ia2 = 22 A, Ia0 = 22 AD. Ia1 = 25.4 A, Ia2 = 12.7 A, Ia0 = 0 A

925. EE Board Exam April 1991 A star-connected balanced load takes 75 A from a balanced 3-phase, 4-wiresupply. If the two supply lines of the fuses are removed determine thesymmetrical components of the lines after the fuses are removed.

A. I1 = 25 A, I2 = 25 A, I3 = 25 AB. I1 = 25 A, I2 = 50 A, I3 = 0 AC. I1 = 75 A, I2 = 75 A, I3 = 75 AD. I1 = 75 A, I2 = 0 A, I3 = 0 A

Zero sequence current = 14.13 cis 17.34°Positive sequence current = 708.26 cis (-31°)Negative sequence current = 2.98 cis 10.06°

Determine the phase a current.

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926. REE Board Exam September 2000

If the loads of a wye-connected transformer are:Ia = 10 cis (-30°)Ib = 12 cis 215°Ic = 15 c is 82°

Find the positive sequence component of phase a current. A. 13.4 cis (-32.2°) C. 12.27 cis 208.4°B. 10.2 cis 240° D. 12.27 cis (-31.6°)

927. The method of symmetrical components is very useful forA. solving unbalanced polyphase circuitsB. analyzing the performance of 3-phase electrical machineryC. calculating currents resulting from unbalanced faultsD. all of the above

928. An un balanced system of 3 -phase voltages having RYB sequence a ctuallyconsists ofA. a positive-sequence componentB. a negative-sequence componentC. a zero-sequence componentD. all of the above

929. The zero-sequence component of the unbalanced 3-phase system of vectorsV A, VB and VC is of their vector sum. A. one-third C. two-thirdB. one-half D. one-fourth

930. In the case of an unbalanced star-connected load supplied from anunbalanced 3- , 3 wire system, load currents will consists ofA. positive-sequence componentsB. negative-sequence componentsC. zero-sequence componentsD. only A and B

931. In symmetrical components, what is the vector sum of 1 + a + a2? A. 1 C. -1B. 0 D. infinity

932. REE Board Exam October 1997The sequence currents of a three phase current are:

A. 720 cis (-30°) C. 710 cis 88°B. 730 cis (-15.2°) D. 695 cis 15.2°

933. REE Board Exam April 2001The three unbalanced currents are:

Ia = 10 cis (-30°)Ib = 0Ic = 10 cis 150°

Find the phase B positive sequence current. A. 8.66 A C. 5.77 AB. 5.77 cis 240° A D. 8.66 cis 120° A

934. REE Board Exam September 2002The phase currents of a three-phase system are:

Ia = 100 cis 0°Ib = 80 cis 240°Ic = 91.8 cis 130.9°

Find the zero sequence current. A. 90.23 cis 3.68° A B. 270.7 cis 3.68° AC. 34.68 cis (-30.24°) AD. none of the above

935. Given three unbalanced three-phase voltages:Va = 150 + j0 VVb = -90 – j120 VVc = -120 + j90 V

Determine Va 1 A. 142.43 + j12.35B. 135.32 – j 1.34C. 145.62 + j13.66D. 140.23 – j9.32

936. A. C.B. D.