
Concept explainers
The reason for the why it is desirable to disconnect the autotransformer from the circuit when the motor reaches the run state.

Explanation of Solution
Consider the autotransformers are used in the starting of the squirrel cage induction motor. The autotransformer reduces the voltage that is applied to the motor to reduce the inrush current at the starting.
As the motor reaches 75% of the normal speed the motor is in the run stage.
As the rotor reach the run stage of the normal speed is applied the full voltage.
After the run stage autotransformer to supply the full load voltage is the waste of energy as the same voltage is applied by connecting the motor to the supply.
Therefore, it is desirable to disconnect the transformer as the motor reaches the run stage to save the energy and extend the life of transformer.
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Chapter 38 Solutions
Industrial Motor Control
- a 300n girl and an 400n boy stand on a 16m platform supported by posts A and B. The platform itself weighs 200N. What are the forces exerted by the supports on the platform?arrow_forwardC A cylindrical piece of steel 38 mm (1½ in.) in diameter is to be quenched in moderately agi- tated oil. Surface and center hardnesses must be at least 50 and 40 HRC, respectively. Which of the following alloys satisfy these requirements: 1040, 5140, 4340, 4140, and 8640? Justify your choice(s).arrow_forwardUsing the isothermal transformation diagram for a 1.13 wt% C steel alloy (Figure 10.39), determine the final microstructure (in terms of just the microconstituents present) of a small specimen that has been subjected to the following time-temperature treatments. In each case assume that the specimen begins at 920°C (1690°F) and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure. (a) Rapidly cool to 250°C (480°F), hold for 103 s, then quench to room temperature. (b) Rapidly cool to 775°C (1430°F), hold for 500 s, then quench to room temperature. (c) Rapidly cool to 400°C (750°F), hold for 500 s, then quench to room temperature. (d) Rapidly cool to 700°C (1290°F), hold at this temperature for 105 s, then quench to room temperature. (e) Rapidly cool to 650°C (1200°F), hold at this temperature for 3 s, rapidly cool to 400°C (750°F), hold for 25 s, then quench to room temperature. (f) Rapidly cool to 350°C (660°F), hold for…arrow_forward
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