Electrical Machines
Questions & Answers
Question 4: DC machine calculations Draw the torque-speed steady state characteristics of the load and the electrical machine for three different points (different speeds, different loads...) • You must get the electrical a mechanical data from the catalogue What type of connection do you use for your machine (independent, series, parallel, compound)? Why? For the three plotted points, calculate the power and current absorbed from the energy source. Assume an ideal variable voltage source Based on week 5 material, describe how you would control the speed of your drive
3.5. /A 150-kVA, 2400/240-V single-phase transformer has the parameters asshown in Figure 3.31. (a) Determine the equivalent circuit referred to the high-voltage side. (b) Find the primary voltage and voltage regulation when transformer is op-erating at full load 0.8 power factor lagging and 240 V. (c) Find the primary voltage and voltage regulation when the transformer isoperating at full-load 0.8 power factor leading. (d) Verify your answers by running the trans program in MATLAB and ob-tain the transformer efficiency curve.
3.3 A 24,000-kVA, 17.32-kV, 60-Hz, three-phase synchronous generator has asynchronous reactance of 5 U phase and negligible armature resistance. (a) At a certain excitation, the generator delivers rated load, 0.8 power factor lagging to an infinite bus bar at a line-to-line voltage of 17.32 kV. Determine the excitation voltage per phase. (b) The excitation voltage is maintained at 13.4 kV/phase and the terminal voltage at 10 kV/phase. What is the maximum three-phase real power that the generator can develop before pulling out of synchronism? (c) Determine the armature current for the condition of part (b).
What is a masked load? How does it occur? Discuss its impact on the distribution circuits.
EEvaluate the following integrals: \text { (a) } \int_{-2}^{2}(2 x+3) \delta(3 x) d x \text { . } \text { (b) } \int_{0}^{2}\left(x^{3}+3 x+2\right) \delta(1-x) d x \text { . } \text { (c) } \int_{-1}^{1} 9 x^{2} \delta(3 x+1) d x \text { . } \text { (d) } \int_{-\infty}^{a} \delta(x-b) d x \text { . }
Three phase, 480V 40 Hz, 6 pole induction motor R_{1}=R_{2}^{\prime}=0.1 \Omega, X_{1}+X_{2}^{\prime}=X_{e q}=0.5 \Omega Full load slip is 3% η = 90% Starting current (ignore magnetizing current) b. Starting torque c. Maximum torque d. Rotor resistance to be added to the rotor circuit to reduce the starting current by 50% e. Starting torque at case d. f. Rotor resistance to be added to the rotor circuit to increase the starting torque tomaximum g. Starting current at f.
