Electrical_Power_Drivers-_ET3026WB-Chapt17_example_questions

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Unformatted text preview: s NOT true? a) As the power rating of synchronous motor increases, so does their efficiency. b) Synchronous motors only generate reactive power. c) Produced reactive power of a synchronous motor increases with an increase of the excitation of the rotor. d) Synchronous motors can have a power factor of unity. Example 17‐2a (Ex) Illustrated the figure below, a 500hp, 720rpm synchronous motor connected to a 3980V, 3‐phase line generates an excitation voltage E0 of 1790V (line‐to‐neutral) when the dc exciting current is 25A. The synchronous reactance is 22Ω and the torque angle between E0 and E is 30o. (Voltage reference is the voltage E) What is the value of Ex? a) 2190V < 0o b) 510V < 0o c) 510V < 50o d) 1168V < 50o. Example 17‐2a (line current) Illustrated the figure below, a 500hp, 720rpm synchronous motor connected to a 3980V, 3‐phase line generates an excitation voltage E0 of 1790V (line‐to‐neutral) when the dc exciting current is 25A. The synchronous reactance is 22Ω and the torque angle between E0 and E is 30o. (Voltage reference is the voltage E) What is the value the ac line current? a) 53A < ‐40o. b) 99,5A < 0o. c) 99,5A < ‐40o. d) 53A < 0o. Example 17‐2a (power factor) Illustrated the figure below, a 500hp, 720rpm synchronous motor connected to a 3980V, 3‐phase line generates an excitation voltage E0 of 1790V (line‐to‐neutral) when the dc exciting current is 25A. The synchronous reactance is 22Ω and the torque ang...
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This note was uploaded on 02/04/2014 for the course EE 1300 taught by Professor Bauer during the Spring '12 term at High Point.

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