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Three 100-MVA single-phase transformers, rated at 13.8 kV Three 100-MVA single-phase transformers, rated at 13.8 kV: 66.4kV, are to be connected in a three-phase bank. Each transformer has a series impedance of 0.0045 + j0.19 ? referred to its 13.8-kV winding. a. If the transformers are connected Y-Y, calculate (i) the voltage and power rating […]

Two coils, one mounted on a stator and the other on a rotor, Two coils, one mounted on a stator and the other on a rotor, have self- and mutual inductances of L11 = 3.5mH L22 = 1.8mH L12 = 2.1cos ? mH where ? is the angle between the axes of the coils. The […]

Two 50-kW, 440-V, three-phase, six-pole, 60-Hz squirrel-cage ind Two 50-kW, 440-V, three-phase, six-pole, 60-Hz squirrel-cage induction motors have identical stators. The dc resistance measured between any pair of stator terminals is 0.204 ft. Blocked-rotor tests at 60-Hz produce the following results. Determine the ratio of the internal starting torque developed by motor 2 to that […]

This problem investigates the advantages of short-pitching the This problem investigates the advantages of short-pitching the stator coils of an ac machine. Figure shows a single full-pitch coil in a two-pole machine. Figure b shows a fractional-pitch coil for which the coil sides are ß radians apart, rather than p radians (180°) as is the […]

The two-winding magnetic circuit of figure has a winding on The two-winding magnetic circuit of figure has a winding on a fixed yoke and a second winding on a moveable element. The moveable element is constrained to motion such that the lengths of both air gaps remain equal. a. Find the self-inductances of windings 1 […]

An inductor of the form of figure has dimensions: An inductor of the form of figure has dimensions: Cross-sectional area Ac = 3.6 cm2 Mean core length lc = 15 cm N = 75 turns Assuming a core permeability of Âľ = 2100Âľ0 and neglecting the effects of leakage flux and fringing fields, calculate the […]

The transformer of Problem 2.11 is to be connected as The transformer of Problem 2.11 is to be connected as an autotransformer. Determine (a) The voltage ratings of the high- and low-voltage windings for this connection and (b) The kVA rating of the autotransformer connection. Is this the question you were looking for? If so, […]

The wound rotor of Problem 11.24 will be used to The wound rotor of Problem 11.24 will be used to drive a constant-torque load equal to the rated full-load torque of the motor. Using the results of Problem 11.24, calculate the external rotor resistance required to adjust the motor speed to 850r/min. Is this the […]

Earned Value Problems PLEASE PICK ONE OF THE (3) PROBLEMS Document Preview: Earned Value Problems Of the three problems below, choose and solve one problem. Show your work. Along with your answer, define each term and explain the significance (meaning) of the solution. 1. During a project, Earned Value Analysis is performed and gives the […]

a. Consider the Y-Y transformer connection of Problem 2.35, a. Consider the Y-Y transformer connection of Problem 2.35, part (b). If the rated voltage is applied to the high-voltage terminals and the three low-voltage terminals are short-circuited, calculate the magnitude of the phase current in per unit and in amperes on (i) the high-voltage side […]