Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Textbook Question
Chapter 4, Problem 15RQ
A three-phase motor nameplate indicates a full load current of 362 amperes. The nameplate indicates that the heaters are to be sized for 125% of motor full load current. Current transformers with a ratio of 600:5 are used to reduce the motor current. Using the chart shown in Figure 4–7B, determine the size of overload heaters needed to protect this motor.
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Understanding Motor Controls
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- 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.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_forwardName three factors that determine the amount of induced voltage.arrow_forward
- Power-consuming devices are wired in _____(series orparallel).arrow_forwardRefer 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 load in question 7 is connected in a wye, what would be the line voltage and line current supplying the load?arrow_forward
- Refer 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_forwardIf 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_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_forward
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