Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 10, Problem 3RQ
To determine
The size of the fuse for primary overcurrent protection.
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A 228 V/ 111 V single-phase transformer has a core loss of 110 W and the no-load current is 0.7 A. The no load power factor is
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A 2 kV / 229 V transformer has the secondary turns of 47. The number of Primary turns of a transformer is given by,
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For the given power transfer, a delta system is associated with larger line currents and a star system is associated with a larger line voltage.
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The following data were obtained on a 50 kVA 2400/120 V transformer:
Open circuit test, instruments on low voltage side:
Waltmeter reading = 396 Watts
Ammeter reading = 9.65 amperes
Voltmeter reading = 120 Volts
Short circuit test, instruments on high voltage side:
Waltmeter reading = 810 Watts
Ammeter reading = 20.8 amperes
Voltmeter reading = 92 Volts
Find the efficiency when rated kVA is delivered to a load having a power
factor of 0.8 lagging.The following data were obtained on a 50 kVA 2400/120 V transformer :
Open circuit test, instruments on low voltage side:
Waltmeter reading = 396 Watts
Ammeter reading = 9.65 amperes
Voltmeter reading = 120 Volts
Short circuit test, instruments on high voltage side:
Waltmeter reading = 810 Watts
Ammeter reading = 20.8 amperes
Voltmeter reading = 92 Volts
Find the efficiency when rated kVA is delivered to a load having a power
factor of 0.8 lagging.
Find the value of the currents I1 and 12.
100 ohm
5V
5V
100 ohm
12
O a. 1=-0.3A, 12=-0.1A
O b. 11=0.3A, 12=0.1A
Oc. 11=0.05A, 12=0.1A
O d. 11=0.1A, 12=0.2A
Chapter 10 Solutions
Electrical Transformers and Rotating Machines
Ch. 10 - Prob. 1RQCh. 10 - What size overcurrent device should be used to...Ch. 10 - Prob. 3RQCh. 10 - The secondary of the transformer in question #3...Ch. 10 - A 10 kVA transformer has a primary voltage of 208...Ch. 10 - A 10 kVA transformer has a primary voltage rating...Ch. 10 - What size conductor should be used to connect the...
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Similar questions
- A 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_forwardA 10 kVA transformer has a primary voltage of 208 volts and a secondary voltage of 120 volts. What size circuit breaker should be used to protect the primary winding?arrow_forwardIf dual-element time delay fuses are to be used as the short circuit protective device, what size fuses should be used to protect the circuit in question #12? Five 5 HP, three-phase motors with NEMA code B are connected to a 240-volt line. The conductors are copper with type THWN insulation. What size conductor should be used to supply all of these motors?arrow_forward
- What size conductor should be used to connect the primary of the transformer described in question #6? Assume the conductor to be copper with type THW insulation.arrow_forwardAn alternator with a line voltage of 2400 V supplies a delta-connected load. The line current supplied to the load is 40 A. Assuming the load is a balanced three-phase load, what is the impedance of each phase?arrow_forwardHow does the National Electrical Code specify that the high leg of a four-wire delta connection be marked?arrow_forward
- What size overcurrent device should be used to protect the primary of a 480/120 volt 15 kVA transformer?arrow_forwardIf dual-element time-delay fuses are to be used as the short-circuit protective device, what size fuses should be used to protect the circuit in question #12?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
- Two transformers rated at 100 kVA each are connected in an open-delta connection. What is the total output power that can be supplied by this bank?arrow_forwardA 480-volt three-phase load is rated at 34.5 kVA. It is to be supplied with variable three-phase voltage. Because the load is continuous, the transformers ratings are to be increased by 1.25% of the rated load. Three variable autotransformers are used to supply this load. Refer to Table 4-2 and determine the standard size of each transformer that should be used to make this connection.arrow_forwardal Three coils each having resistance of 29 N are connected in star across 422 V, 50 Hz supply. Then the total power consumed is O 211.77 W O 3545.51 W O 730.95 W O 6140.83 Warrow_forward
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