Electric machinery fundamentals
5th Edition
ISBN: 9780073529547
Author: Chapman, Stephen J.
Publisher: MCGRAW-HILL HIGHER EDUCATION
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Textbook Question
Chapter 2, Problem 2.12Q
What are the problems associated with the Y—Y three-phase transformer connection?
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Students have asked these similar questions
For an ideal 2-winding transformer, an impedance Z2 connected across winding 2 (secondary)
is referred to winding 1 (primary) by multiplying Z2 by
(a) The turns ratio (N1/N2)
(b) The square of the turns ratio (N1/N2)2
(c) The cubed turns ratio (N1/N2)3
In no load phasor diagram of practical
transformer, the magnetizing current Imag is
with primary voltage
Vp.
90° out of phase
Leading by 30°
Lagging by 60°
In phase
In no load phasor diagram of practical transformer, the magnetizing current Imag is
with primary voltage Vp.
In phase
Lagging by 60°
90°out of phase
Leading by 60°
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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- The direct electrical connection of the windings allows transient over voltages to pass through the auto transfonner more easily, and that is an important disadvantage of the autotransformer. (a) True (b) Falsearrow_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_forwardThe ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer. (a) True (b) Falsearrow_forward
- In 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_forwardThree 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_forwardConsider the oneline diagram shown in Figure 3.40. The three-phase transformer bank is made up of three identical single-phase transformers, each specified by X1=0.24 (on the low-voltage side), negligible resistance and magnetizing current, and turns ratio =N2/N1=10. The transformer bank is delivering 100 MW at 0.8 p.f. lagging to a substation bus whose voltage is 230 kV. (a) Determine the primary current magnitude, primary voltage (line-to-line) magnitude, and the three-phase complex power supplied by the generator. Choose the line-to-neutral voltage at the bus, Va as the reference Account for the phase shift, and assume positive-sequence operation. (b) Find the phase shift between the primary and secondary voltages.arrow_forward
- In 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_forwardFor an ideal 2-winding transformer, the ampere-turns of the primary winding, N1I1 is equal to the ampere-turns of the secondary winding, N2I2 (a) True (b) Falsearrow_forwardWhat should be the focus of transformer preventive maintenance efforts?arrow_forward
- For developing per-unit equivalent circuits of single-phase three-winding transformer, a common Sbase is selected for all three windings and voltage bases are selected in proportion to the rated voltage of the windings (a) True (b) Falsearrow_forwardA 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_forwardAn ideal transformer has no real or reactive power loss. (a) True (b) Falsearrow_forward
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