Electrical Machines

A 13 kV, 40-MVA, 0.8-power-factor-lagging, 60-Hz, 8-poles Y-connected synchronous generator has a synchronous reactance of 2.5 2 and an armature resistance of 0.2 2. At 60 Hz, its friction and windage losses are 1 MW, and its core losses are 1.5 MW. The field circuit has a de voltage of 120 V, and the maximum field current is 10 A. The current of the field circuit is adjustable over the range from 0 to 10 A. 1. Draw the open circuit characteristics [OCC] for this generator. Assume that this characteristics is represented by the following relation: 2. Draw the short circuit characteristics [SCC] for this generator. Assume that this characteristics is represented by the following relation: 3. Draw the synchronous impedance (Xs) of this generator as a function of the armature current. 4. Draw the per phase equivalent circuit of the 3-Phase synchronous generator. 5. Draw the terminal voltage (V₁) versus the armature current (1) of this generator up to the rated load current for the following cases [One graph]: A. Rated MVA with 0.8-PF-lagging load. B. Rated MVA with 0.8-PF-leading load. C. Rated MVA with unity load. 6. Draw the voltage regulation (VR) versus the armature current (1) of this generator up to the rated load current for the following cases [One graph]: A. Rated MVA with 0.8-PF-lagging load. B. Rated MVA with 0.8-PF-leading load. C. Rated MVA with unity load. 7. Draw the losses of this synchronous generator as a function of the armature current (1). 8. Draw the efficiency of the synchronous generator (n) as a function of the load current (1) up to the rated current. 9. Draw the developed torque of this synchronous generator as a function of armature current (1). 10. Draw the rotor angle (8) of this synchronous generator as a function of armature current (1).

Three single phase transformers are used to form a three phase transformer bank \text { - } 138 \mathrm{kV}(\Lambda) / 120 \mathrm{kV}(\mathrm{Y}) Source is a 120kV transmission line. ●Load side is a 12 MVA load at 0.8 Lagging PF. a. Turns ratio of each transformer. b. Line current at the 120 kV side.

) 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

l: Find the current I, in the network given in the figure by using MESH ANALYSIS.

3.8. Three identical 9-MVA, 7.2-kV/4.16-kV, single-phase transformers are connected in wye on the high-voltage side and delta on the low voltage side. The equivalent series impedance of each transformer referred to the high-voltage side is 0.12+ j0.82 O per phase. The transformer supplies a balanced three-phase load of 18 MVA, 0.8 power factor lagging at 4.16 kV. Determine the line-to-line voltage at the high-voltage terminals of the transformer.

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?

Match the following according to the type of motor load: a. Constant power loads b. Variable torque load c. Constant torque load

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

2. Now add a disturbance to the system with the “Band-Limited White Noise" block in the Simulink library. Open the block and set the “Noise power" to "20" and the "Sampletime" to "n 002 " Provide a screenshot of your updated Simulink Block Diagram and controller. Provide a screenshot of the noise (using a scope). Provide a screenshot of the new outnut (usingscone) c. Comment on your output (e.g., Does it stay within 1% of your desired set point?Do you still meet the overshoot requirements?). 1 What could this noise represent in a real-world application?