Practice Session 3

# Practice Session 3 - ECSE 462 PRACTICE SESSION III October...

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ECSE 462 PRACTICE SESSION III October 2009 Refer to Lecture 12. Question 1: From Fig. 1 below show that “airgap power is synchronous speed ω multiplied by the torque.” S I ~ M j ω S j A R j A + S E ~ + m R E ~ m R R S R R I ~ Fig. 1 is developed from (10) + + + = + + + = ) ~ ~ ( ~ ) ( ~ ) ~ ~ ( ~ ) ( ~ R S R R R R R S S S S S I I M j I j S R S E I I M j I j R E A A The stator airgap voltage () mS S S S EE Rj I =− + ±± ± A can also be written as: R E jMI I =+ ± (A) The active power passing to the airgap from the stator is * Re airgap m S PE I = (B) Question : What is the symbol * for? Substitute (A) in (B) and 12 S I ij i ± , 34 R I i = + ± . Show that airgap e PT = . (C)

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From (B) you can show that 14 23 () airgap e PM i i i i T ω = −= as ( ) SR e M ii ii M i i i i T γδ δγ = Note that the airgap power is not the active real power of the inductive reactance j M . An inductive reactance does not take active power. From equation (B), it is the active power associated with stator current S I ± entering the airgap whose voltage is seen as m E ± .
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Practice Session 3 - ECSE 462 PRACTICE SESSION III October...

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