A no-load test Conducted a three-phase Connected induction Motor. gave the Following values. No-load Poyter = 890 w Stator resistance, per phase. at 30°C = 0.233 olims. No-load current = 14₁SA Calculate the fixed losses for the Motor

Rotor resistance of a three-phase induction motor is 0.080 per phase. Maximum torque is available at the slip of 12%. Calculate the equivalent load resistance, load voltage and load current at this slip. Gross output power is 9 kW. zwoll E2 1₂ INSTR₂=0.08001 od X₂ boobs Yo not www YOUR voor R₁ R₂(1/S-1) constaies sidsiuv od lliw sad jedanss

T-a. The direction of rotation of a single-phase split-phase motor can be change by........ a) reversing the connection of the start winding b) reversing the connection of the run winding c) reversing the connection of the start and run winding at the same time d) "a" or "b", not "c" T-b. Single-phase split-phase motors using an electrolytic capacitor in the start winding circuit should not be cycled more than about__________ time per hour. a) 8 b) 12 c) 24 d) none of the above T-c. When replacing the capacitor in a capacitor-start induction-run motor, one must be sure to replace the bad capacitor with__________ . a) a smaller one b) one of the same size c) a larger one d) none of the above

Q3 A 50 Hz split-phase induction motor has a resistance of 50 and an inductive reactance of 200 in the main winding as well as starting winding. Determine the value of resistance and capacitance to be added in series with the starting winding to send the same current in each winding with a phase difference of 90°. Ans[ 14.99 Ω, 127.5μF]

• - 1800 pm In a two pole 3-p synchronous generator, the peak flux of rotor magnetic field is o5Tand the rotor rate of rotation is 1800 rpm. The stator windings have a surface area of 0.1 m? and there are 50 turns per Bmax : 0.5T, 0.5T coil. The machine is A-connected. A: 0-1 m? N: 50 a) What is the RMS phase and line voltage of the generator? b) Write the three stator phase voltages as functions of time.

and t A common base of 100 MVA and 25 KV is selected. What is the current base (Ig) Select one: O a. 4 KA O b. None of these O c. 6.25 kA O d. 2.309 KA A 100-MVA, 60-kV, three-phase synchronous generator has a synchronous reactance of armature resistance. The generator is operating with an excitation per phase E= 47.116 power before losing synchronism (stability limit). and the armature c Thus, the maximum generated power is Pmax =

Question -9b

6- Which of the following supply is given to the rotor winding of 3-Phase Induction Motor: a) DC Supply b) AC Supply c) No Supply d) Pulsating Supply 7- 3-Phase Induction Motor will have Starting Torque and Starting Current a) High, High b) Low, Low. c) High, Low d) Low, High 8- Which of the following method is used for controlling the speed of an induction motor: a) Changing number of stator poles b) Supply voltage control c) Frequency control d) All the options are correct 9- Which of the following method cannot be used for starting of 3-Phase Squirrel Induction Motor: a) Star-Delta Starting b) Line resistor startling c) transformer Starter d) Rotor Resistance Starting 10- The rotor of a stepper motor has no: a) windings b) commutator c) brushes d) all of the above

The synchronous reactance of an alternator represents A reactance connected in series with a synchronous generator Field winding reactance and armature reaction reactance Armature reaction reactance and leakage reactance Leakage reactance and field winding reactance

A 3-0, 50-Hz induction motor with its rotor star-connected gives 500 V (r.m.s.) at standstill between slip-rings on open circuit. Calculate the current and power factor in each phase of the rotor windings at standstill when joined to a star-connected circuit, each limb of which has a resistance of 10 Q and an inductance of 0.03 H. The resistance per phase of the rotor windings is 0.2 Q and inductance 0.03 H. Calculate also the current and power factor in each rotor phase when the rings are short- circuited and the motor is running with a slip of 4 per cent. [13.6 A, 0.48; 27.0 A, 0.47] (London University) A 4-pole, 50-Hz, 3-phase induction motor has a slip-ring rotor with a resistance and standstill reactance of 0.04 2 and 0.2 2 per phase respectively. Find the amount of resistance to be inserted in each rotor phase to obtain full-load torque at starting. What will be the approximate power factor in the rotor at this instant ? The slip at full-load is 3 per cent. [0.084 2, 0.516 p.f.]…