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The flux densities of the magnetic fields created in the air gap by each of the three stator currents of a three-phase 2-pole ac machine are given respectively for phases a, b, and c by the equations below, where alpaha is the angular position in the air gap (alpha = 0 corresponds to the phase a axis).
B a = B M cos(omega t) cos(alpha);
B b = B M cos [omega t - 2 pi/3) cos (alpha - 2 pi/d);
B c = B M cos (omega t + 2 pi/3) cos (alpha + 2 pi/3).
Each equation above describes a field that is distributed sinusoidally and whose amplitude varies sinusoidally with time (a pulsating field). Prove for the resultant magnetic flux density in the air gap (a) at any given t, the flux density is distributed sinusoidally with respect to alpha; and (b) the center of the flux rotates around the air gap at an angular velocity equal omega. That is, prove that B(t, alpha) = B a + B b, + B a = 2/3 BM cos(omega t - alpha).
A 150 MVA, 24 kV, 125% three-phase synchronous generator supplies a large network. The network voltage is 27 kV. The generator operates with an induced voltage, which is twice the rated line-to-neutral voltage.
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The generator is delivering 48 MW to the bus bar at the rated voltage with its field current adjusted for a generated emf of 46 kV per phase. Determine the armature current and the power factor. State whether power factor is lagging or leading
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What is the effect of a frequency difference between the carrier and local oscillator on output quality? Show mathematically.
The charge carried by an electron is ?1.60×10?19 C. Suppose that an electron moves through a voltage of 120V from the negative polarity to the positive polarity. How much energy is transferred Does the electron gain or lose energy
A three phase synchronous motor has the synchronous reactance of 2.1 Ohm and draws 250 A with a lagging power factor for an excitation voltage of 1327 -15 degree per phase. Find the terminal voltage of the motor and power factor of the motor.
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