Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 8, Problem 3RQ
To determine
Whether the line values of voltage and current be used or the phase values while computing the voltage and current in three phase transformer.
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Question 7
In no-load phasor diagram of the transformer, the core loss component current is
with primary voltage.
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O in phase
O Perpendicular & in phase
Question 8
In an A.C. circuit, the power measured by using wattmeter is
power.
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Question 9
In step up transformer, secondary turns are less than primary turns.
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O False
The arc length voltage characteristic of a DC arc is given by the equation V=24+4L where
'V' is the arc voltage in volts and L' is the length in mm. The static volt-ampere
characteristic of the power source is approximated by a straight line with no load voltage of
80V and the short circuit current of 600A. Then the optimum arc length is
(mm).
A transformer transforms
(a) frequency
(b) voltage
(c) current
(d) voltage and current.
2. Which of the following is not a basic element of
a transformer?
(a) core
(b) primary winding
(c) secondary winding
(d) mutual flux.
3. In an ideal transformer,
(a) windings have no resistance
(b) core has no losses
(c) core has infinite permeability
(d) all of the above.
4. The main purpose of using core in a transformer
is to
(a) decrease iron losses
(b) prevent eddy current loss
(c) eliminate magnetic hysteresis
(d) decrease reluctance of the common mag-
netic circuit.
1
Chapter 8 Solutions
Electrical Transformers and Rotating Machines
Ch. 8 - How many transformers are needed to make an...Ch. 8 - Two transformers rated at 100 kVA each are...Ch. 8 - Prob. 3RQCh. 8 - Assume that a line voltage of 2400 volts is...Ch. 8 - Prob. 5RQCh. 8 - How much current is flowing through the secondary...Ch. 8 - How much current is flowing through the primary...Ch. 8 - Prob. 8RQCh. 8 - Prob. 9RQCh. 8 - How much current is flowing in the secondary...
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Similar questions
- An AC power source is connected across 325 turns of an autotransformer, and the load is connected across 260 turns. What is the turns ratio of this transformer?arrow_forwardWhat are the three types of opposition to current flow that impedance represents?arrow_forwardAssume that a line voltage of 2400 volts is connected to the primary of the three-phase transformer and the line voltage of the secondary is 240 volts. What is the turns ratio of the transformer?arrow_forward
- A three-phase transformer connection has a delta-connected primary and a wye-connected secondary. The center tap of the wye is used as a neutral conductor. If the line-to-line voltage is 480 volts, what is the voltage between any one phase conductor and the neutral conductor?arrow_forwardAn open-delta three-phase transformer system has one transformer center-tapped to provide a neutral for single-phase voltages. If the voltage from line to center tap is 277 volts, what is the high-leg voltage?arrow_forwardA 10 kVA transformer has a primary voltage rating of 240 volts and a secondary voltage rating of 480 volts. The transformer is connected to a circuit protected by a 100 ampere circuit breaker. The secondary is protected by a 25-ampere fuse. Does the primary require separate overcurrent protection?arrow_forward
- 8. An R-L series circuit has a reactive power of 1234 VARs and an apparent power of 4329 VA. By how many degrees are voltage and current out of phase with each other? 9. An R-L series circuit contains a resistor and an inductor. The resistor has a value of 6.5 22. The circuit is connected to 120 V and has a current flow of 12 A. What is the inductive reactance of this circuit? 10. What is the voltage drop across the resistor in the circuit in Question 9? 11. A phase angle meter connected in an R-L series circuit indicates that the current is 28 degrees out of phase with the voltage. What is the circuit power factor? 12. An R-L series circuit has a power factor of 73%. If the apparent power is 560 kVA, what is the true power in the circuit?arrow_forwardWhat is the peak voltage of a 120V RMS AC voltage?arrow_forwardA load impedance of 52 Ω is connected to the secondary winding of the transformer in question 3. How much current will flow in the secondary?arrow_forward
- Four inductors, each having an inductance of 0.6 H, are connected in series. What is the total inductance of the circuit?arrow_forwardA transformer has a primary voltage of 240 volts and a secondary voltage of 48 volts. What is the turns ratio of this transformer?arrow_forwardThe value of Vg-Vf at critical point is * O infinity two O one zeroarrow_forward
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