Which оf the fоllоwing is а physicаl аctivity recommendation for children and adolescents (6-17 years old)?
Exаm 3 Instructiоns: Clоsed bоok, closed notes, no crib sheet, no cаlculаtor. Put your student ID on each page. You must show work for credit. Your answers can have a factor of (2/3), 3{"version":"1.1","math":"3"}, π{"version":"1.1","math":"π"}, etc. in them and so only make those numerical simplifications that could reasonably be made without a calculator. Answers must be reasonably simplified. Honorlock must remain running until you finish submitting your work. For your trigonometric convenience: Exam 3 - Problem 1. (25 pts) Consider an inverter with an input voltage of 100V, a forward switch drop of 2V, and a forward diode of 1V. The inverter is sin-triangle modulated and . The modulation index (i.e, d) was 0.8. At an instant of time, the upper switch of the a-phase leg, the lower switch of the b-phase leg, and the upper switch of the c-phase leg are gated on. The remaining switches are gated off. At that instant the rotor position is zero. The values of the a-phase and b-phase currents are 25A and -10A, respectively. The inverter is connected to an ideal wye-connected PMAC machine. Recall and . Find the following at the described instant of time: , , ( instantaneous values) ,, (instantaneous values; assume ideal PMAC machine) (instantaneous value) , (neglect semiconductor drops, fast average values) Recall Exam 3 - Problem 2. (10 pts) Draw a three-phase bridge inverter, showing the connections to a PMAC machine. Assume the machine is star-connected. Mark relevant currents, relevant voltages, and appropriate nodes, like ‘g’ and ‘n’. Exam 3 - Problem 3. (10 pts) Draw the circuit diagram showing pulse width modulation logic that generates the six gate signals T1-T6. Exam 3 - Problem 4. (2 pts) Under what assumptions can I consider a PMAC to be a R-L load? Exam 3 - Problem 5. (3 pts) What is the advantage of using Extended Sine Triangle Modulation over 180 VSI and over Sine Triangle Modulation? Exam 3 - Problem 6. (25 pts) A three-phase induction machine is connected to a rad/s utility and is driven mechanically to the operating point shown in the figure below. All reference angles for analysis are defined positive in the counterclockwise direction (as done in class). For the operating condition shown in the figure where , fill in tables I and II. You’ll need to copy these over to your solution sheet. Note/hint: In order to find the number of poles in this machine, think in terms of the slip frequency when Te=0. Also noting, that zero torque occurs when and is provided. Exam 3 - Problem 7. (25 pts) Recall that for a three-phase induction machine, torque may be expressed It can be shown that loss is given by Recall that we derived an expression for the radian slip frequency which minimizes stator current while yielding a desired torque. Derive the value of the radian slip frequency which minimizes loss while achieving a desired torque. Your answer will be an expression in terms of machine parameters, ,,,. Hint: Begin with the loss expression and substitute the currents before proceeding with your derivative. Exam 4 Instructions: Closed book, closed notes, no crib sheet, no calculator. Put your student ID on the front of the exam, not your name. Answers must be reasonably simplified Honorlock must remain running until you finish submitting your work. Exam 4 - Problem 1. (4 pts) Suppose H=5xax+4ay{"version":"1.1","math":"H=5xax+4ay"} A/m where ax{"version":"1.1","math":"ax"} and ay{"version":"1.1","math":"ay"} are unit vectors in the x- and y-direction. What is the MMF drop from point (1,0) to (2,0)? Exam 4 - Problem 2. (4 pts) Why do ferri- and ferro-magnetic materials saturate? Exam 4 - Problem 3. (4 pts) Suppose B=5xcos(25t)ax+4ay{"version":"1.1","math":"B=5xcos(25t)ax+4ay"}. A winding with 10 turns surrounds a surface S=2ay{"version":"1.1","math":"S=2ay"}. The coil is open circuited. What is the voltage across the coil? Exam 4 - Problem 4. (4 pts) What are the key assumptions in using a short circuit test to determine the leakage inductances of a single-phase power transformer? Exam 4 - Problem 5. (4 pts) A transformer feeds a resistance load of 2 Ohms on the secondary. The primary-to-secondary turns ratio is 10. What is the resistance used for the load when using the T-equivalent circuit. Exam 4 - Problem 6. (20 pts; 2 pts each) Short answer, no derivation. A.) What geometrical features of the PMAC machine give rise to cogging torque? B.) What are two reasons we use the QD transformation for the PMAC machine? C.) Name two attributes of the PMAC machine. D.) Why don’t we use phasors to analyze steady-state behavior of the PMAC? E.) Could we have used the stationary reference frame transformation on the PMAC? F.) Could we have used the rotor reference frame transformation on the IM? G.) Name two physical effects that cause the IM model to not work that well. H.) Name two types of IM rotors. I.) Name two attributes of induction machines. J.) Why is dysprosium added to Nd-FeB permanent magnets? Exam 4 - Problem 7. (2 pts) What causes loss of synchronism in a variable reluctance stepper motor? Exam 4 - Problem 8. (2 pts) Using a relevant equation, explain why starting current is high in a PMDC machine. Exam 4 - Problem 9. (3 pts) What is the difference between voltage-source and current-source operation of an inverter? Provide one modulation technique (as example) for each kind of operation. Exam 4 - Problem 10. (2 pts) Which of the following is a physical quantity and which among them is a mathematical construct? - Field energy -Co-energy Exam 4 - Problem 11. (5 pts) An ideal PMAC is from an inverter which is extended sine-triangle modulated. The dc voltage is 100V and ϕv=0{"version":"1.1","math":"ϕv=0"}. The inverter is producing the most voltage it can without producing low-frequency harmonics. What are the q- and d-axis voltages? What is the value of d3? Exam 4 - Problem 12. (5 pts) An inverter fed PMAC is fed from a 100V source. The fast averages of the q-axis voltage, d-axis voltage, q-axis current, and the d-axis current are 40V, 10V, 10A, and -10A respectively. Estimate the fast average of the dc current into the inverter. Exam 4 - Problem 13. (4 pts) In the Volts per hertz control of the induction machine, what is SRL and what is it used for? Exam 4 - Problem 14. (4 pts) For a conservative electrical system with one winding and no mechanical degree of freedom, the current through the winding and the flux linking the winding are 1 A and 5 Vs respectively. The co-energy at this state is 2 J. What is the corresponding field energy? Exam 4 - Problem 15. (7 pts) Consider a PM dc machine fed from a converter. Suppose ra=0.5Ω, kv=0.1Vs{"version":"1.1","math":"ra=0.5Ω, kv=0.1Vs"}, and Laa=1mH{"version":"1.1","math":"Laa=1mH"}. The converter is in discontinuous mode. If the peak armature current is 10 A, and it takes 100 µs for the current to fall to zero after the switch turns off, what is the speed of the machine in rad/s. You may assume the diode voltage drop is zero. Exam 4 - Problem 16. (8 pts) Consider a machine with the following a-phase winding function: How many a-phase conductors are coming out of slot 3? Exam 4 - Problem 17. (10 pts) A single-phase induction machine has a single winding on the stator and a single winding on the rotor. The flux linkage equations are λas=6ias+3cos(2θrm)iarλar=6iar+3cos(2θrm)ias{"version":"1.1","math":"λas=6ias+3cos(2θrm)iarλar=6iar+3cos(2θrm)ias"} Derive an expression for torque in terms of the currents and mechanical rotor position. Exam 4 - Problem 18. (2 pts) If the number of stator U cores in a transverse flux machine is 80. How many rotor poles does the machine have? Exam 4 - Problem 19. (2 pts) In a Dual Rotor Homopolar AC Machine, how are the frequencies of the auxiliary winding related to the main winding? Exam 4 - Problem 20. (2 pts) Does the transverse flux homopolar AC machine (THAM) have magnets on the stator or the rotor? Exam 4 - Problem 21. (2 pts) What type of induction machine is used in wind generation systems? What kind of machine did we consider and analyze in the class? Congratulations, you are almost done with Exam 3 & Exam 4. DO NOT end the Honorlock session until you have submitted your work to Brightspace. When you have answered all questions: Use your smartphone or scanner to scan your answer sheet, and save the scan as a PDF. Make sure your scan is clear and legible. Submit your PDFs as follows: Email your PDF to yourself or save it to the cloud (Google Drive, etc.). Submit your exams to these assignments: Exam 3 Submission Exam 4 Submission Return to this window and click the button below to agree to the honor statement. 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If а muscle rаn оut оf ATP whаt wоuld be the result?