Superconducting synchronous machines are designed with supercond Superconducting synchronous machines are designed with superconducting fields windings which can support large current densities and create large magnetic flux densities. Since typical operating magnetic flux densities exceed the saturation flux densities of iron, these machines are typically designed without iron in the magnetic circuit; as a result, […]
Thermal considerations limit the field-current of the Thermal considerations limit the field-current of the laboratory-size synchronous generator of Problem 4.18 to a maximum value of 2.4 A. If the peak fundamental air-gap flux density is limited to a maximum of 1.3 T, calculate the maximum torque (N 路 m) and power (kW) which can be […]
An inductor is made up of a 525-turn coil on An inductor is made up of a 525-turn coil on a core of 14-cm2 cross-sectional area and gap length 0.16 mm. The coil is connected directly to a 120-V 60-Hz voltage source. Neglect the coil resistance and leakage inductance. Assuming the coil reluctance to be […]
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.