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Electric machinery fundamentals
5th Edition
ISBN: 9780073529547
Author: Chapman, Stephen J.
Publisher: MCGRAW-HILL HIGHER EDUCATION
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Chapter 2, Problem 2.15Q
To determine
To explain: The reason for supplying 57.7 percent of normal Δ-Δ transformer bank load by an open delta transformer connection.
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Chapter 2 Solutions
Electric machinery fundamentals
Ch. 2 - Is the turns ratio of a transformer the same as...Ch. 2 - Why does the magnetization current impose an upper...Ch. 2 - What components compose the excitation current of...Ch. 2 - What is the leakage flux in a transformer? Why is...Ch. 2 - List and describe the types of losses that occur...Ch. 2 - Why does the power factor of a load affect the...Ch. 2 - Why does the short-circuit test essentially show...Ch. 2 - Why does the open-circuit test essentially show...Ch. 2 - How does the per-unit system of measurement...Ch. 2 - Why can autotransformers handle more power than...
Ch. 2 - What are transformer taps? Why are they used?Ch. 2 - What are the problems associated with the Y—Y...Ch. 2 - What is a TCUL transformer?Ch. 2 - How can three-phase transformation be accomplished...Ch. 2 - Prob. 2.15QCh. 2 - Can a 60-Hz transformer be operated on a 50-Hz...Ch. 2 - What happens to a transformer when it is first...Ch. 2 - What is a potential transform? How is it used?Ch. 2 - What is a current transformer? How is it used?Ch. 2 - A distribution transformer is rated at 18 kVA,...Ch. 2 - Why does one hear a hum when standing near a large...Ch. 2 - A 100-kVA, 8000/277-V distribution transformer has...Ch. 2 - A single-phase power system is shown in Figure...Ch. 2 - Consider a simple power system consisting of an...Ch. 2 - The secondary winding of a real transformer has a...Ch. 2 - When travelers from the USA and Canada visit...Ch. 2 - A 1000-VA, 230/115-V transformer has been tested...Ch. 2 - A 30-kVA, 8000/230-V distribution transformer has...Ch. 2 - A 150-MVA, 15/200-kV, single-phase power...Ch. 2 - A 5000-kVA, 230/13.8-kV, single-phase power...Ch. 2 - A three-phase transformer bank is to handle 500...Ch. 2 - A 100-MVA, 230/115-kV, Y three-phase power...Ch. 2 - Three 20-kVA, 24,000/277-V distribution...Ch. 2 - A 14,000/480-V, three-phase, Y-connected...Ch. 2 - A 13.8-kV, single-phase generator supplies power...Ch. 2 - An autotransformer is used to connect a 12.6-kV...Ch. 2 - Prove the following statement: If a transformer...Ch. 2 - A 10-kVA, 480/120-V conventional transformer is to...Ch. 2 - A 10-kVA, 480/120-V conventional transformer is to...Ch. 2 - Two phases of a 14.4-kV, three-phase distribution...Ch. 2 - A 50-kVA, 20,000/480-V, 60-Hz, single-phase...Ch. 2 - Prove that the three-phase system of voltages on...Ch. 2 - Prove that the three-phase system of voltages on...Ch. 2 - A single-phase, 10-kVA, 480/120-V transformer is...Ch. 2 - Figure P2-4 shows a one-line diagram of a power...
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- A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters: Resistance of the 2400-V winding: R1=0.75 Resistance of the 240-V winding: R2=0.0075 Leakage reactance of the 2400-V winding: X1=1.0 Leakage reactance of the 240-V winding: X2=0.01 Exciting admittance on the 240-V side =0.003j0.02S (a) Draw the equivalent circuit referred to the high-voltage side of the transformer. (b) Draw the equivalent circuit referred to the low-voltage side of the transformer. Show the numerical values of impedances on the equivalent circuits.arrow_forwardThe ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA Secondary (2): Y connected, 13.2kV,10MVA Tertiary (3): A connected, 2.3kV,5MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X12=0.08 on a 15-MVA,66-kV base X13=0.10 on a 15-MVA,66-kV base X23=0.09 on a 10-MVA,13.2-kV base (a) Determine the per-unit reactances X1,X2,X3 of the equivalent circuit on a 15-MVA,66-kV base at the primary terminals. (b) Purely resistive loads of 7.5 MW at 13.2 kV and 5 MW at 2.3kV are connected to the secondary and tertiary sides of the transformer, respectively. Draw the per- unit impedance diagram, showing the per-unit impedances on a 15-MVA,66-kV base at the primary terminals.arrow_forwardThe ratings of a three-phase, three-winding transformer are Primary: Y connected, 66kV,15MVA Secondary: Y connected, 13.2kV,10MVA Tertiary: connected, 2.3kV,5MVA Neglecting resistances and exciting current, the leakage reactances are: XPS=0.09 per unit on a 15-MVA,66-kV base XPT=0.08 per unit on a 15-MVA,66-kV base XST=0.05 per unit on a 10-MVA,13.2-kV base Determine the per-unit reactances of the per-phase equivalent circuit using a base of 15 MVA and 66 kV for the primary.arrow_forward
- Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.arrow_forwardAn ideal transformer has no real or reactive power loss. (a) True (b) Falsearrow_forwardA single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer has a 1-ohm equivalent leakage reactance and a 5000-ohm magnetizing reactance referred to the high-voltage side. If rated voltage is applied to the high-voltage winding, calculate the open-circuit secondary voltage. Neglect I2RandGc2V losses. Assume equal series leakage reactances for the primary and the referred secondary.arrow_forward
- Rework Problem 3.14 if the transformer is delivering rated load at rated secondary voltage and at (a) unity power factor, (b) 0.8 power factor leading. Compare the results with those of Problem 3.14. -arrow_forwardIn per-unit equivalent circuits of practical three-phase transformers, under balanced thr-phase operation, in which of the following connect ions would a phase-shifting transformer come up? (a) Y-Y (b) Y- (c) -arrow_forwardIn developing per-unit circuits of systems such as the one shown in Figure 3.10. when moving across a transformer, the voltage base is changed in proportion to the transformer voltage ratings. (a) True (b) Falsearrow_forward
- The ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer. (a) True (b) Falsearrow_forwardWhy is it important to reduce the moisture within a transformer to acceptable levels during transformer installation?arrow_forwardWith the American Standard notation, in either a Y-or-Y transformer, positive- sequen quantities on the high-voltage side shall lead their corresponding quantities on the low-voltage side by 30. (a) True (b) Falsearrow_forward
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