Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Chapter 5, Problem 7RQ
A 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.
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Students have asked these similar questions
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.
Please help me solve this question
A balanced star-connected load of (8 + j6) Q per phase is connected to a Balanced 3- phase 400-V supply. Find the line current, power factor, power
Chapter 5 Solutions
Electrical Transformers and Rotating Machines
Ch. 5 - An AC power source is connected across 325 turns...Ch. 5 - Is the transformer in question 1 a step-up or...Ch. 5 - Prob. 3RQCh. 5 - A load impedance of 52 Ω is connected to the...Ch. 5 - How much current will flow in the primary of the...Ch. 5 - Prob. 6RQCh. 5 - A 480-volt three-phase load is rated at 34.5 kVA....Ch. 5 - If the load in question 7 was supplied by two...Ch. 5 - Prob. 1PCh. 5 - Prob. 2P
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- 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_forwardRefer to the transformer shown in Figure 5-13 to answer the following questions. What is the turns ratio of the winding between points B and E as compared to the winding between points D and E? Figure 5-13 Autotransformer practice problems.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
- 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_forwardName three factors that determine the amount of induced 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
- If the load in question 7 was supplied by two autotransformers connected in open delta, what would be the minimum standard size transformers that could be used to supply this load?arrow_forwardQuestion 2 Beli vifth Slack side Motor (imprut) Tight side Beli thickpess\ Centre distance Figure 2 Figure 2 shows an open flat belt drive connected to a motor and a pulley. The motor transmits 20 kw to the connect pulley of 450 mm diameter and is rotating at 850 r/min to a second pulley rotating at 400 r/min. The distance between pulley centres is approximately 2 m. The belt is 6 mm thick and has a density of 970 kg/m. The maximum stress in the belt is not to exceed 2,7 MPa. The coefficient of friction for both pulleys is 0,3. Determine: 2.1. The diameter of the second pulley. 2.2. The length of the belt. 3.3. The width of the belt taking centrifugal tension into account.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_forward
- How many transformers are needed to make an open-delta connection?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_forwardA large motor has a full load current rating of 425 amperes. Current transformers with a ratio of 600:5 are used to reduce the current to the overload heaters. What should be the full load current rating of the overload heaters?arrow_forward
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