A two-pole, 60-Hz three-phase laboratory-size synchronous A two-pole, 60-Hz three-phase laboratory-size synchronous generator has a rotor radius of 5.71 cm, a rotor length of 18.0 cm, and an air-gap length of 0.25 mm. The rotor field winding consists of 264 turns with a winding factor of kr = 0.95. The Y-connected armature winding consists of […]
For a synchronous machine with constant synch For a synchronous machine with constant synchronous reactance Xs operating at a constant terminal voltage Vt and a constant excitation voltage Eaf, show that the locus of the tip of the armature-current phasor is a circle. On a phasor diagram with terminal voltage shown as the reference phasor, […]
A transformer is to be used to transform the impedance A transformer is to be used to transform the impedance of a 8-⌠resistor to an impedance of 75 ft. Calculate the required turns ratio, assuming the transformer to be ideal.
A squirrel-cage induction motor runs at a full-load slip of A squirrel-cage induction motor runs at a full-load slip of 3.7 percent. The rotor current at starting is 6.0 times the rotor current at full load. The rotor resistance and inductance is independent of rotor frequency and rotational losses, stray-load losses and stator resistance may […]
A two-phase permanent-magnet ac motor has a rated speed of A two-phase permanent-magnet ac motor has a rated speed of 3000 r/min and a six-pole rotor. Calculate the frequency (in Hz) of the armature voltage required to operate at this speed.
Figure shows the general nature of the slot-leakage flux produce Figure shows the general nature of the slot-leakage flux produced by current i in a rectangular conductor embedded in a rectangular slot in iron. Assume that the iron reluctance is negligible and that the slot leakage flux goes straight across the slot in the region […]
For the potential transformer of Problem 2.29, find the maximum For the potential transformer of Problem 2.29, find the maximum reactive burden (minimum reactance) which can be applied at the secondary terminals such that the voltage magnitude error does not exceed 0.5 percent.
For each of the following changes in operating condition for For each of the following changes in operating condition for a dc shunt motor, describe how the armature current and speed will vary: a. Halving the armature terminal voltage while the field fluxes and load torque remain constant. b. Halving the armature terminal voltage while […]
For a 25-kW, 230-V, three-phase, 60-Hz squirrel-cage motor opera For a 25-kW, 230-V, three-phase, 60-Hz squirrel-cage motor operating at rated voltage and frequency, the rotor I2R loss at maximum torque is 9.0 times that at full-load torque, and the slip at full-load torque is 0.023. Stator resistance and rotational losses may be neglected and the […]
A superconducting magnet has an inductance of 4.9 H, A superconducting magnet has an inductance of 4.9 H, a resistance of 3.6 mO, and a rated operating current of 80 A. It will be supplied from a 15-V rms, three-phase source through a three phase, phase-controlled bridge. It is desired to “charge” the magnet at […]