exam2[1]

exam2[1] - ECE321 Exam II Fall 2009 Last Name First Name...

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ECE321 Exam II Fall, 2009 Last Name:_____________________________ First Name:_____________________________ User ID (login):___________________ Work problems and provide answers in space provided - do not unstaple pages 1-page crib allowed (to be submitted with exam). No calculators
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1. Consider the following multi-stack variable-reluctance (VR) stepper motor . (a) (b) (c) (d) (e) Initially, , , and . Then, is set to 0 and to 1 A ( is still zero). . At the new equilibrium, sketch the stator poles ( and ), and the rotor position in the figure below. Indicate which tooth is shaded. as rm θ rm θ rm θ as’ as as’ bs bs’ bs bs’ cs cs’ cs’ cs L max 3 mH = L min 1 mH = SL _____________ ° = L asas θ rm () _____ ______ ______ θ _________ ° [] cos mH + = L bsbs θ _____ ______ ______ θ _________ ° mH cos + = L asbs θ _____ ______ ______ θ _________ ° mH cos + = θ 0 = i as 1 A = i bs i cs 0 == i i i T L 0 = N S θ _________ ° = bs bs bs’ bs’ (25) [O i-ii]
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2. The static torque-versus-position characteristics of a VR stepper motor are depicted below for one- phase-on-at-a-time excitation. (a) Can we tell whether or not the motor is a single-stack or multi-stack device? If so, which is it? Explain briefly.
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exam2[1] - ECE321 Exam II Fall 2009 Last Name First Name...

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