Electrical Machines
Questions & Answers
Question 1: Historical context and background Describe the historical background of the application (timeline, first prototype, development...) Identify at least two of the most common topologies of the electric drive used for your vehicle. Include diagrams Name the main parts of one of the electric drive topologies and describe their function • What is the most common electrical machine used in your vehicle? Why? Include diagrams State the technical specifications of your vehicle (weight, number of passengers...) This section should be less than 3 pages
Discuss the measures to mitigate EV load impacts by upgrading the distribution system infrastructure.
) Explain how induction motors' speed can be controlled by frequency (for the below rated speed and above rated speed), include a sketch of the circuit configuration. The results of the no load and blocked rotor parameter tests on a 400 kW, 3300 V, three phase, 4 pole, 50 Hz, Y connected, squirrel cage induction motor is shown below: i. Calculate the no load core loss? ii. Calculate the equivalent circuit parameters in Ohms including R₁, R2, X₁ and X2 Assume that X₁ = X₂. iii.Provide a diagram of a single-phase equivalent circuit for this induction motor(referring to stator side), labelling the components clearly and indicated the supply voltage correctly. Considering the same induction motor as Q( 4b) and presuming the motor is operating at rated voltage and frequency, with a slip of 2.8 % and stator current value of l₁ = 68.01<-15.93° A, calculate the following parameters: i. Motor's Power factor? ii. Input power? iii. Stator losses?
Justify your answer for the following questions: DC motors use permanent magnets to construct a static magnetic field. If a motor consumes 184 kW of power but only produces 231 HP at the shaft, itscurrent operating efficiency isanswer to the nearest one.% (1 Horsepower = 745.7 Watts). Round your c) Induction motors use commutators to transmit current to the rotor, thus producing a rotor magnetic field. A live reading of a motor indicates that it is consuming 16.4 kVA with a Power Factorof 0.76. You also know the current operating efficiency of the motor is 89%. What is theinstantaneous power output of the motor? (1 Horsepower = 745.7 Watts).%3D
Why would you prefer to place the field winding on the rotor of synchronous machine?Answer in not more than 2 sentence.
Find the decimal numbers represented by the Single Precision Floating PointRepresentation (SPFP) values. 43 92 BО 00 С4 0С 30 00
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 50-Hz, two-pole, 750 kVA, 2300 V, three-phase synchronous machine hasa synchronous reactance of 7.75 2 and achieves rated open-circuit terminalvoltage at a field current of 120 A. Calculate the armature-to-field mutual inductance. The machine is to be operated as a motor supplying a 600 kW load at its rated terminal voltage. Calculate the internal voltage Eaf and the corresponding field current if the motor is operating at unity power factor. c. For a constant load power of 600 kW, write a MATLAB script to plot the terminal current as a function of field current. For your plot, let the field current vary between a minimum value corresponding to a machine loading of 750 kVA at leading power factor and a maximum value corresponding to a machine loading of 750 kVA at lagging power factor.What value of field current produces the minimum terminal current? Why?
A 60 Hz, 360 V, 3 phase, 6 pole, Y-connected induction motor is driving a load at 1100 rpm.The combined friction, windage and stray power losses are 200 W. The motor parameters referred to the stator are (i) Draw the per phase approximate equivalent circuit for the motor. (ii) Find the slip (iii) Calculate the equivalent rotor current. (iv) Determine the stator copper loss and rotor copper loss. (v) Determine the developed mechanical power. (vi) Find the output torque
