# hw6 - to get the same torque as we had in the original...

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EE321 Spring 2008 / Homework 6 VR Stepper Design. For Problems 25-26 Consider the stepper motor design we did in class. Our design had two coils connected in series. Each of these coils had N/2 turns. Let us now take these two coils and tie them in parallel rather than in series. Problem 25 Compute the aligned and unaligned inductance for this machine (in terms of N and a R and u R ). See slides 48-49. If we used a current I in our original design to produce a desired torque, what will be the total current we need now (for example I 2 or 2 / I ). Problem 26 Compute the expression for resistance in terms of w l , σ , and c a . In this case, keep in mind the wire length is divided into two parallel segments. See slide 44. How much voltage will we need
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Unformatted text preview: to get the same torque as we had in the original design. (In other words, if the dc voltage was dc V before, and ignoring semiconductor drops, will we need dc V 2 , 2 / dc V or something else ?) Problem 27 – Problem 3.10-3 from Electromechanical Motion Devices Problem 28 – Problem 3.10-6 from Electromechanical Motion Devices Problem 29 – PM DC Machine Performance A PM DC machine has a back emf constant of 0.1 Vs, and an armature resistance of 300 m Ω . The armature voltage is 25 V, and the load torque may be expressed 3 400 2 ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = r l T ω Find the rotor speed, the armature current, and the efficiency....
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