Problem 3.1MCQ: The Ohms law for the magnetic circuit states that the net magnetomotive force (mmf) equals the... Problem 3.2MCQ: For an ideal transformer, the efficiency is (a) 0 (b) 100 (c) 50 Problem 3.3MCQ: For an ideal 2-winding transformer, the ampere-turns of the primary winding, N1I1 is equal to the... Problem 3.4MCQ: An ideal transformer has no real or reactive power loss. (a) True (b) False Problem 3.5MCQ: For an ideal 2-winding transformer, an impedance Z2 connected across winding 2 (secondary) is... Problem 3.6MCQ: Consider Figure 3.4. For an ideal phase-shifting transformer, the imda nce is unchanged when it is... Problem 3.7MCQ: Consider Figure 3.5. Match the following, those on the left to those on the right. (i) Im (a)... Problem 3.8MCQ: The units of admittance, conductance, and susceptance are siemens. (a) True (b) False Problem 3.9MCQ: Match the following: (i) Hysteresis loss (a) Can be redud by constructing the core with laminated... Problem 3.10MCQ: For large power transformers rated more than 500 kVA, the winding resistances, which are small... Problem 3.11MCQ: For a short-circuit test on a 2-winding transformer, with one winding shorted, can you apply the... Problem 3.12MCQ: The per-unit quantity is always dimensionless. (a) True (b) False Problem 3.13MCQ: Consider the adopted per-unit system for the transformers. Specify true or false for each of the... Problem 3.14MCQ: The ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer.... Problem 3.15MCQ: To convert a per-unit impedance from old to new base values, the equation to be used is... Problem 3.16MCQ: In developing per-unit circuits of systems such as the one shown in Figure 3.10. when moving across... Problem 3.17MCQ Problem 3.18MCQ Problem 3.19MCQ: With the American Standard notation, in either a Y-or-Y transformer, positive- sequen quantities on... Problem 3.20MCQ Problem 3.21MCQ: In order to avoid difficulties with third-harmonic exciting current, which three-phase transformer... Problem 3.22MCQ: Does an open connection permit balanced three-phase operation? - (a) Yes (b) No Problem 3.23MCQ: Does an open- operation, the kVA rating compared to that of the original thr-phase bank is (a) 2/3... Problem 3.24MCQ: It is stated that (i) balanced three-phase circuits can be solved in per unit on a per-phase basis... Problem 3.25MCQ: In developing per-unit equivalent circuits for three-phase transformers. under balanced three-phase... Problem 3.26MCQ: In per-unit equivalent circuits of practical three-phase transformers, under balanced thr-phase... Problem 3.27MCQ Problem 3.28MCQ Problem 3.29MCQ: For developing per-unit equivalent circuits of single-phase three-winding transformer, a common... Problem 3.30MCQ Problem 3.31MCQ Problem 3.32MCQ Problem 3.33MCQ: The direct electrical connection of the windings allows transient over voltages to pass through the... Problem 3.34MCQ: Consider Figure 3.25 of the text for a transformer with off-nominal turns ratio. (i) The per-unit... Problem 3.1P: (a) An ideal single-phase two-winding transformer with turns ratio at=N1/N2 is connected with a... Problem 3.2P: An ideal transformer with N1=1000andN2=250 is connected with an impedance Z22 across winding 2. If... Problem 3.3P: Consider an ideal transformer with N1=3000andN2=1000 turns. Let winding 1 be connected to a source... Problem 3.4P: A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down... Problem 3.5P Problem 3.6P Problem 3.7P: Consider a source of voltage v(t)=102sin(2t)V, with an internal resistance of 1800. A transformer... Problem 3.8P Problem 3.9P Problem 3.10P: A single-phase step-down transformer is rated 13MVA,66kV/11.5kV. With the 11.5 kV winding... Problem 3.11P: For the transformer in Problem 3.10. The open-circuit test with 11.5 kV applied results in a power... Problem 3.12P Problem 3.13P: A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer has a 1-ohm equivalent leakage... Problem 3.14P: A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down... Problem 3.15P: Rework Problem 3.14 if the transformer is delivering rated load at rated secondary voltage and at... Problem 3.16P: A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters:... Problem 3.17P: The transformer of Problem 3.16 is supplying a rated load of 50 kVA at a rated secondary voltage of... Problem 3.18P: Using the transformer ratings as base quantities, work Problem 3.13 in per-unit. Problem 3.19P: Using the transformer ratings as base quantities. work Problem 3.14 in per-unit. Problem 3.20P: Using base values of 20 kVA and 115 volts in zone 3, rework Example 3.4. Problem 3.21P Problem 3.22P: A balanced Y-connected voltage source with Eag=2770volts is applied to a balanced-Y load in parallel... Problem 3.23P: Figure 3.32 shows the oneline diagram of a three-phase power system. By selecting a common base of... Problem 3.24P: For Problem 3.18, the motor operates at full load, at 0.8 power factor leading, and at a terminal... Problem 3.25P: Consider a single-phase electric system shown in Figure 3.33. Transformers are rated as follows:... Problem 3.26P: A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a... Problem 3.27P: A three-phase transformer is rated 1000MVA,220Y/22kV. The Y-equivalent short-circuit impedance,... Problem 3.28P: For the system shown in Figure 3.34. draw an impedance diagram in per unit by choosing 100 kVA to be... Problem 3.29P: Consider three ideal single-phase transformers (with a voltage gain of ) put together as ... Problem 3.30P: Reconsider Problem 3.29. If Va,VbandVc are a negative-sequence set, how would the voltage and... Problem 3.31P Problem 3.32P: Determine the positive- and negative-sequence phase shifts for the three- phase transformers shown... Problem 3.33P: Consider the three single-phase two-winding transformers shown in Figure 3.37. The high-voltage... Problem 3.34P: Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance... Problem 3.35P: Consider a bank of this single-phase two-winding transformers whose high-voltage terminals are... Problem 3.36P: Three single-phase two-winding transformers, each rated 25MVA,34.5/13.8kV, are connected to form a... Problem 3.37P: Three single-phase two-winding transformers, each rated 25MVA,54.2/5.42kV, are connected to form a... Problem 3.38P: Consider a three-phase generator rated 300MVA,23kV, supplying a system load of 240 MA and 0.9 power... Problem 3.39P: The leakage reactance of a three-phase, 300-MVA,230Y/23-kV transformer is 0.06 per unit based on its... Problem 3.40P Problem 3.41P: Consider the single-line diagram of the power system shown in Figure 3.38. Equipment ratings are... Problem 3.42P: For the power system in Problem 3.41, the synchronous motor absorbs 1500 MW at 0.8 power factor... Problem 3.43P: Three single-phase transformers, each rated 10MVA,66.4/12.5kV,60Hz, with an equivalent series... Problem 3.44P: A 130-MVA,13.2-kV three-phase generator, which has a positive-sequence reactance of 1.5 per unit on... Problem 3.45P: Figure 3.39 shows a oneline diagram of a system in which the three-phase generator is rated 300 MVA,... Problem 3.46P: The motors M1andM2 of Problem 3.45 have inputs of 120 and 60 MW, respectively, at 13.2 kV, and both... Problem 3.47P: Consider the oneline diagram shown in Figure 3.40. The three-phase transformer bank is made up of... Problem 3.48P: With the same transformer banks as in Problem 3.47, Figure 3.41 shows the oneline diagram of a... Problem 3.49P: Consider the single-Line diagram of a power system shown in Figure 3.42 with equipment ratings... Problem 3.50P: A single-phase three-winding transformer has the following parameters: Z1=Z2=Z3=0+j0.05,Gc=0, and... Problem 3.51P: The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA... Problem 3.52P Problem 3.53P: The ratings of a three-phase, three-winding transformer are Primary: Y connected, 66kV,15MVA... Problem 3.54P: An infinite bus, which is a constant voltage source, is connected to the primary of the... Problem 3.55P: A single-phase l0-kVA,2300/230-volt,60-Hz two-winding distribution transformer is connected as an... Problem 3.56P: Three single-phase two-winding transformers, each rated 3kVA,220/110volts,60Hz, with a 0.10 per-unit... Problem 3.57P: A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when... Problem 3.58P: A single-phase two-winding transformer rated 90MVA,80/120kV is to be connected as an autotransformer... Problem 3.59P Problem 3.60P: PowerWorid Simulator case Problem 3_60 duplicates Example 3.13 except that a resistance term of 0.06... Problem 3.62P: Rework Example 3.12 for a+10 tap, providing a 10 increase for the high-voltage winding. Problem 3.63P: A 23/230-kV step-up transformer feeds a three-phase transmission line, which in turn supplies a... Problem 3.64P: The per-unit equivalent circuit of two transformers Ta and Tb connected in parallel, with the same... Problem 3.65P: Reconsider Problem 3.64 with the change that now Tb includes both a transformer of the same turns... Problem ACSQ: What are the advantages of correctly specifying a transformer most Suita ble for its application? Problem BCSQ: Why is it important to reduce the moisture within a transformer to acceptable levels during... Problem CCSQ: What should be the focus of transformer preventive maintenance efforts? format_list_bulleted
Delmar's Standard Textbook Of ElectricityElectrical EngineeringISBN:9781337900348Author:Stephen L. HermanPublisher:Cengage Learning