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# hw5 - Initialize the c-phase is energized and the position...

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EE321 Spring 08 Homework 5 Problem 21 – Stepper Motor Characterization Your measure the series resistance / inductance of a stepper motor with a series LCR meter. As you rotate the machine the resistance is constant and is equal to 3.3 Ohms. The inductance varies between 10 mH and 120 mH. Also, the inductance has 8 maximum as you rotate the shaft through a revolution. What is the stator resistance, the number of rotor teeth, A ls L L + , and B L ? Note: you will not be able to separate ls L from A L with the given information. Problem 22 – Stable Equilibrium Point Consider a variable reluctance stepper motor with 4 rotor teeth. Suppose that B L is 200 mH. The a- and c-phases are energized with a current of 1 A. Suppose further that the load torque is 0.15 Nm. Find the stable equilibrium point closest to zero. Problem 23 – Torque Versus Position Trajectory Consider the torque versus position characteristics of a VR stepper shown below.
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Unformatted text preview: Initialize the c-phase is energized and the position is as indicated (point 1). Then the position is stepped to the b-phase. Circle the resulting stable equilibrium point and mark with a 2. Then the a-phase is excited. Circle and mark the stable equilibrium point with a 3. Continue in this fashion as the c-phase, b-phase, and finally a-phase are each excited a 2 nd time (thus the final point should be labeled 6). Problem 24 – Machine Configuration It is desired that a stepper motor has a step length of 10 degrees. (This is for normal step operation). It is desired that the number of rotor teeth is less than 8 and than that the number of phases is less than 8. Sketch the configuration of such a machine. Your answer should be analogous to Fig 8.2-3 of Electromechanical Motion Devices ....
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