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The permanent-magnet dc motor of Problem 11.8 is operating at The permanent-magnet dc motor of Problem 11.8 is operating at its rated speed of 3000 r/min and no load. If rated current is suddenly applied to the motor armature in such a direction as to slow the motor down, how long will it take the […]

The manufacturer calculates that the transformer of Problem 2.7 The manufacturer calculates that the transformer of Problem 2.7 has a secondary leakage inductance of 0.225 mH. a. Calculate the magnetizing inductance as referred to the secondary side. b. A voltage of 266 V, 60 Hz is applied to the secondary. Calculate (i) the resultant open-circuit […]

The resistances and leakage reactance’s of a 30-kVA, 60-Hz, The resistances and leakage reactance’s of a 30-kVA, 60-Hz, 2400-V: 240-V distribution transformer are R1 = 0.68 ? R2 = 0.0068 ?, X11 = 7.8 ? X12 = 0.0780 ? where subscript 1 denotes the 2400-V winding and subscript 2 denotes the 240-V winding. Each quantity […]

The manufacturer’s data sheet for a permanent-magnet dc motor The manufacturer’s data sheet for a permanent-magnet dc motor indicates that it has a torque constant Km = 0.21 V/(rad/sec) and an armature resistance of 1.9O. For a constant applied armature voltage of 85 V dc, calculate a. The no-load speed of the motor in r/min […]

The resistance measured between each pair of slip rings of a he resistance measured between each pair of slip rings of a three-phase, 60-Hz, 250-kW, 16 poles, and wound-rotor induction motor is 49 mO. With the slip tings short-circuited, the full-load slip is 0.041. For the purposes of this problem, it may be assumed that […]

The plunger of a solenoid is connected to a spring. The plunger of a solenoid is connected to a spring. The spring force is given by f = K0 (0.9a – x), where x is the air-gap length. The inductance of the solenoid is of the form L = L0 (1 – x/a), and its […]

The phase windings of the castleated machine of Figure are The phase windings of the castleated machine of Figure are to be excited by turning the phases on and off individually (i.e., only one phase can be on at any given time). a. Describe the sequence of phase excitations required to move the rotor to […]

The permanent magnet motor of Problem 11.17 is to be The permanent magnet motor of Problem 11.17 is to be operated under vector control using the following algorithm. Terminal voltage not to exceed rated value, Terminal current not to exceed rated value iD = 0 unless flux weakening is required to avoid excessive armature voltage. […]

The nameplate on a 7.97-kV: 460-V, 75-kVA, single-phase The nameplate on a 7.97-kV: 460-V, 75-kVA, single-phase transformer indicates that it has a series reactance of 12 percent (0.12 per unit). a. Calculate the series reactance in ohms as referred to (i) the low-voltage terminal and (ii) the high-voltage terminal. b. If three of these transformers […]

The open-circuit terminal voltage of a three-phase, 60-Hz synchr The open-circuit terminal voltage of a three-phase, 60-Hz synchronous generator is found to be 15.4 kV rms line-to-line when the field current is 420 A. a. Calculate the stator-to-rotor mutual inductance Laf. b. Calculate the open-circuit terminal voltage if the field current is held constant while […]