Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 10, Problem 6RQ
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?
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A transformer has a primary voltage of 480 volts and a secondary voltage of 20 volts. What is the turns ratio of the transformer?
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.
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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- A 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_forwardTwo 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_forwardWhat is a special hazard encountered in large industrial transformers used in unit substations?arrow_forward
- What is the peak voltage of an AC circuit which has an RMS voltage of 115V?arrow_forwardFind 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=0.2Aarrow_forwardWhat is the peak voltage of a 120V RMS AC voltage?arrow_forward
- Refer to the transformer shown in Figure 5-13 to answer the following questions. The transformer shown in Figure 5-13 is supplying 325 volt amperes to a load. The primary voltage is 240 volts. What is the primary current? Figure 5-13 Autotransformer practice problems.arrow_forwardIf the secondary of the transformer in question 5 supplies a current of 9.6 amperes to a load, what is the primary current? (Disregard excitation current.)arrow_forwardA transformer has an output of 750 VA. The primary voltage is 120 V. What is the primary current?arrow_forward
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