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Motor Homework Solution

# Motor Homework Solution - ME 350 – Motor Homework –...

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Unformatted text preview: ME 350 – Motor Homework – Fall 2011 Problem 1: Cost Maturity Lifetime Issues (wear, replacing parts, fatigue, etc) Robustness (vibration, impact, rough loadings, etc) Controllability Electrical 3 1 Hydraulic 2 1 Shape Memory Alloy Piezoelectric 4 1 4 3 3 4 1 2 3 1 2 4 2 3 4 1 Problem 2: a) For a DVD/CD drive, it is important to have a relatively constant motor speed so music and movies do not experience slow‐down or speed‐up. Also, computers tend to use lower voltages easily controlled by electronics, and considering he small inertial load of a disc, a DC motor would be appropriate. Finally, because of the sensitivity of floppy discs and other electrical components to magnetic fields, permanent magnets are not a desirable feature. Al of these factors point towards a shunt wound DC motor. These can be made fairly small and inexpensively, two other factors that make them attractive for this application. b) Since the application is industrial, an AC motor would be preferable to DC because transformers would not be needed. The main driving constraint for this application is the conveyor belt speed. Since multiple units are going to be used to drive the same belt, any speed discrepancies could cause the belt to buckle or be excessively stretched. Therefore, AC synchronous motors would be the proper selection. Since they run at a single speed with little variation and without the need for any control, they would be an economical design choice. Problem 3: a) Rotary load IL = 0.02 kg∙m2 with gear reducer. Select motor with minimum power dissipation and minimum temperature rise. Find optimal gear ratio. 1. Minimum power dissipation – motor with minimum electromechanical time constant Select motor 2 0.2 3 ∙ 10 ∙ ∙ 25.8 2. Minimum temperature rise – motor with largest power rate Select motor 3 0.2 1 ∙ 10 ∙ 4.5 ∙ b) Mass M = 7.5 kg Select motor with minimum temperature rise and find optimal radius size Minimum temperature rise – motor with largest power rate Select Motor 3 Optimal pulley radius – inertia matching Mass 1 ∙ 10 0.75 ∙ 0.037 3.7 Problem 4: Rotating antenna 0.8 Gearbox 10:1 ‐‐ N=10 Find motor voltage: Start‐up torque problem ‐‐ Lecture note “Power Energy Conversion” slides 13 & 14 1. Find required load acceleration 2 (from rest) 2 2 2 10 ∙ 2 20 / 2. Find Inertia 0 3. Find startup torque 0.8 100 0.008 ∙ 0.008 20 0.5 96.5 4. Find Voltage 96.5 ∙ 0 (starting up th there is no speed) V = 10 v olts v T = 96.5 0 ∙ ...
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