ECE320_4-3-09 - Exam 3 Monday April 13th Chapter 5 Three...

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Exam 3: Monday, April 13th Chapter 5: Three Phase Windings (Textbook Sections 4.3-4.7) Chapter 6: Induction Machines (Textbook Sections 6.1-6.5) Comments on the Synchronous Motor: Consider a conventional synchronous motor equipped with two poles. It has a DC voltage applied to the rotor winding and a three-phase AC voltage applied to the stator winding (usually 60 (Hz)). The three-phase voltage produces in the stator an ampere-conductor distribution which revolves at a rate of 60 (Hz). The DC currents in the rotor set up a two-pole flux field which is stationary so long as the rotor is not turning. Thus we have a situation in which there exists a pair of revolving armature (or equivalent stator) poles and a pair of stationary rotor poles. Under this condition, every half cycle, a positive torque is developed by the cooperation of the field flux and the revolving ampere-conductor distribution in the stator. In the next half cycle, this torque is reversed to the average torque is zero. This is the reason that a synchronous motor per se has no starting torque.
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ECE320_4-3-09 - Exam 3 Monday April 13th Chapter 5 Three...

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