Electrical Machines

Design and specify the ratings of a single-phase transformer to supply several loads from 600-V source. The design must include the determination of the transformer's kVA rating, and specifications of its primary and secondary currents. It should also attempts to determine the efficiency of the transformer under different loading conditions (LD's). Starting a transformer generally requires more current than running it at its normal LD. To account for this additional current requirement, it's often helpful to put a start factor of 20% extra into the design calculations. a. Consider additional future loads of 10% of current total load capacity). b. Calculate the total kVA required for the transformer (including the additional future loads and the starting factor). c. Use the typical "Standard Transformer Sizes"; see table below. d. Determine the primary and secondary currents of the transformer. e. Determine the full load capacity in kW. f. Calculate the full load efficiency using the following assumption: 1. The core losses are equal to 600-W + XX-W; XX is your last two digits serial number as posted in BB under EE306 common sections (e.g., 01, 04, 10, 14, 21 ...etc.) 2. The full load copper losses are equal to 900-W+Y-W; Y is your one digit section number as posted in BB under EE306 common sections (e.g., 1, 2, 6...etc.) g. Calculate the efficiency of at least 3 different loading scenarios of your own choice (e.g., LDs1: Air Conditions & Lighting; LDs2: Laundry & Kitchen equipment; etc.) h. Calculate the maximum efficiency of the transformer when operating at a power factor of 0.9

Multiwinding transformer from Figure 11.6 Primary: N1=10,000, N2=5,000, N3=1,000 ●Source voltage is 120V applied to the primary Load connected to terminal 2: 600W, 300Var inductive. Load connected to terminal 3: 24 W and 36 Var Capacitive power Secondary winding voltages b. All winding currents

1. What is the ratio of the number of primary to secondary turns in the transformer?

1. A star connected 15 hp, 400 V, six pole, 50 Hz wound rotor induction motor has a stator to rotor turns ratio of 5 : 3. The rotor winding is also star connected. If the motor is connected to the rated voltage source at 50 Hz and the motor runs at 960 rpm.Determine: a) The operating slip of the motor. b) The induced voltage in the rotor winding per phase and its frequency. c) Speed (rpm) of the rotor field BR w.r.t the (i) rotor, (ii) stator. If the stator winding is short-circuited and the power supply is connected to the rotor winding while the motor runs at 970 rpm, determine: d) The direction of rotation of the motor w.r.t to the rotating magnetic field. e) Induced voltage in the stator winding per phase and its frequency.

State the advantages and disadvantages of an auto transformer

A 100-hp 440-V 0.8-PF-leading Delta-connected synchronous motor has an armature resistance of 0.220 and a synchronous reactance of 3.00. Its efficiency at full load is 89 percent. (a) What is the input power to the motor at rated conditions? (b) What is the line current and phase current of the motor at rated conditions? (c) What is the reactive power consumed by or supplied by the motor at rated conditions? (d) What is the internal generated voltage EA of this motor at rated conditions? (e) What is the torque angle of this motor? (f) What are the stator copper losses in the motor at rated conditions? (g) What is Pconv at rated conditions?

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 { . }

State and explain the two types of transformer core losses. How do you minimise them? You are invited for an interview at Transformer Inc. for the position of a design engineer. In the interview, you are given a 10kVA, 2400/347 V, 50Hz transformer with leakage reactance of X₁ = 4.300 and X₂ = 0.090 on the high voltage (HV) and low voltage (LV) sides,respectively. You are also given the HV and LV resistance values of 5.160 and 0.095 respectively. The magnetising reactance XM, of the transformer and the Core loss, Rc referred to the HV side are given as 18.80 and 0.850 respectively. You are asked to do a quick approximation of various design values including the currents on the LV and HV sides of the transformer. (i) Figure. Q2(b) shows the equivalent circuit of the transformer with parameters referred to the LV (secondary) side. From the given values, explain why you should neglect the magnetising branch (XM and Rc) in simplifying your circuit for approximate design calculations.For the remaining parts of Q2(b), consider the approximated circuit with the magnetising branch removed. (ii) Short circuit the secondary terminal of the equivalent circuit shown in Figure Q2(b)and calculate, the short circuit current, I2,sc with rated supply voltage. (iii) Comment on the value of 12,sc current obtained in (ii) above and recommend the correct precaution for short circuit transformer test. (iv) If the transformer is now operating at rated load drawing rated full load current at a power factor of 0.85 lagging, determine the rated current flowing in the secondary winding of the transformer. Present your answer in polar form. (v) Determine the no-load and full-load secondary terminal voltage of the transformer? (vi)Compare the two values, no-load and full-load secondary terminal voltage obtained in (v) above. Are they the same? If not, why? (vii) When carrying full load current, as described in (iv) above, the total core loss of the transformer is constant at 800 W. Determine the transformer copper loss on the LV side and hence, the total transformer loss at this operating condition.

A nuclear power plant produces power with a current of 30.0 kA. A transformer with 1000 windings in the primary circuit and 6000 windings in the secondary circuit is used to step up the potential difference to 250 kV. How much power does the nuclear plant produce? Assume that there is no energy lost in the step-up transformer. (13.5, 13.6) TA

Question 2: Determine the steady state torque Determine the steady state torque for your vehicle. The steady state load is complex to obtain. It is recommended to identify relevant literature but you can try to calculate it. Some references are [1] and [2]. Answer the following questions: Obtain the steady state torque (calculated/from reference) Describe the process of obtaining the steady state torque for your vehicle (main experiments and or equations) What are the variables affecting the steady state torque? Can the steady state torque be approximated as a function? Plot the steady state torque using Excel or Matlab