EE 4420 Topics for Mid-Semester Test 2 I. Rotating magnetic field:-Representation of alternating magnetic field and elliptic rotating magnetic field by two circular magnetic field illustrated by means of magnetic flux phasor diagrams-Conditions for generating of rotating (elliptic) magnetic field and circular magnetic field-Functions that describe alternating magnetic field and rotating magnetic field-Equation for rotary speed expressed in terms of frequency and number of magnetic poles.-Expression for voltage induced in the 3-phase winding of the AC machine.-Conditions for producing of nonzero torque in electric machines. II. Induction Motors 1. Principle of operation of induction machines. Differences in the structure of slip-ring and squirrel-cage motors. 2. Rotor slip equation; relations between: the frequency f 2 and f 1 , voltages E 2o and E 2 ; three modes of operation of induction machine illustrated on the rotor speed and slip axes and relations between stator and rotor frequencies. 3.
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Magnetic Field, Electric motor, II. Induction Motors