Electric Machinery 6th. Edition by A. E. Fitzgerald, Charles Kingsley Jr., Stephen Umans | 9780071121934 | 0073660094 | Holooly

Electrical Machines

Electric Machinery

117 SOLVED PROBLEMS

Question: 9.5

A two-pole, single-phase induction motor has the following parameters Lmain = 80.6 mH Rmain = 0.58 Ω Laux = 196 mH Raux = 3.37 Ω Lr = 4.7 μH Rr = 37.6 μΩ Lmain,r = 0.588 mH Laux,r= 0.909 mH It is operated from a single-phase, 230-V rms, 60-Hz source as a permanent-split-capacitor motor with ...

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MATLAB, with its ease of handling complex numbers,...

Question: 8.3

Consider the idealized 4/2 VRM of Example 8.1. Assume that it has a winding resistance of R = 1.5 Ω/phase and a leakage inductance Ll= 5 mH in each phase. For a constant rotor speed of 4000 r/min, calculate (a) the phase-1 current as a function of time during the interval -60° ≤ θm ≤ 0°, assuming ...

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a. From Eq. 8.15, the differential equation govern...

Question: 8.4

Consider a symmetrical two-phase 4/2 VRM whose λ-i characteristic can be represented by the following λ-i expression (for phase 1) as a function of θm over the range 0 ≤ θm ≤ 90° λ1=(0.005+0.09(90°- θm / 90°)(8.0 / 8.0+i1))i1 Phase 2 of this motor is identical to that of phase 1, and there is no ...

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a. The

λ_1-i_1

curves are shown in ...

Question: 8.2

Consider a four-phase, 8/6 VRM. If the stator phases are excited sequentially, with a total time of T0 sec required to excite the four phases (i.e., each phase is excited for a time of T0/4 sec), find the angular velocity of the stator flux wave and the corresponding angular velocity of the rotor. ...

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Figure 8.7 shows in schematic form an 8/6 VRM. The...

Question: 7.9

A permanent-magnet dc motor is known to have an armature resistance of 1.03 Ω. When operated at no load from a dc source of 50 V, it is observed to operate at a speed of 2100 r/min and to draw a current of 1.25 A. Find (a) the torque constant Km, (b) the no-load rotational losses of the motor and ...

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a. From the equivalent circuit of Fig. 7.20, the g...

Question: 8.6

Consider again the two-phase, permanent-magnet stepping motor of Example 8.5. Calculate the rotor position which will result if the phase currents are controlled to be sinusoidal functions of a reference angle θref in the form i1=I0 cos θref i2=I0 sin θref ...

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Substitution of the current expressions into the t...

Question: C.1

A two-pole synchronous machine is carrying balanced three-phase armature currents ia = √2Ia cos ωt ib = √2Ia cos (ωt – 120°) ic = √2Ia cos (ωt + 120°) The rotor is rotating at synchronous speed ω, and the rotor direct axis is aligned with the stator phase-a axis at time t = 0. Find the direct- ...

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The angle between the rotor direct axis and the st...

Question: 11.12

The three-phase, 230-V, 60-Hz, 12-kW, four-pole induction motor of Example 6.7 and Example 11.11 is to be driven by a field-oriented speed-control system (similar to that of Fig. 11.21b) at a speed of 1740 r/min. Assuming the controller is programmed to set the rotor flux linkages λDR to the ...

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We must first determine the parameters for this ma...

Question: B.2

The two-pole stator-winding distribution of Fig. B.2 is found on an induction motor with an air-gap length of 0.381 mm, an average rotor radius of 6.35 cm, and an axial length of 20.3 cm. Each stator coil has 15 turns, and the coil phase connections are as shown in Fig. B. 10. Calculate the phase ...

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Note that the placement of the coils around the st...

Question: B.1

Calculate the breadth, pitch, and winding factors for the distributed fractional-pitch winding of Fig. B.2. ...

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The winding of Fig. B.2 has two coils per phase be...

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