Electrical Machines Minimum allowable resistivity of power transformer insulating oil is generally taken as 3 X 1012 Ω - cm at 27°C and 0.3 X 1012 1 X 1012 Ω - cm at 27°C and 0.1 X 1012 4 X 1012 Ω - cm at 27°C and 0.4 X 1012 2 X 1012 Ω - cm at 27°C and 0.2 X 1012 3 X 1012 Ω - cm at 27°C and 0.3 X 1012 1 X 1012 Ω - cm at 27°C and 0.1 X 1012 4 X 1012 Ω - cm at 27°C and 0.4 X 1012 2 X 1012 Ω - cm at 27°C and 0.2 X 1012 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines When maximum flux density is constant, the eddy current losses are proportional to V2 V f f2 V2 V f f2 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Consider the following statements regarding the magnetization characteristics of a dc generator : 1. It represents the variation of field flux with field current. 2. Variation of open-circuit terminal voltage with field current is independent of speed 3. It is non-linear from zero to rated field current 4. It helps to determine the critical field resistance at a given speed 5. It always starts from the origin Which of these statements are correct ? 1, 2 and 5 1 and 4 3 and 5 2, 3 and 4 1, 2 and 5 1 and 4 3 and 5 2, 3 and 4 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Consider the following statements : For a level compounded dc generator to run at constant voltage, the series field mmf must effectively compensate 1. armature reaction mmf 2.armature resistance drop 3. brush contact voltage drop Which of these statements is/are correct ? 2 alone 1, 2 and 3 1 and 2 1 and 3 2 alone 1, 2 and 3 1 and 2 1 and 3 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 4 pole dc motor with armature winding resistance of 0.6 ohm receives a supply of 230 Volt. If the back emf produced during running condition is equal to 210 volt. Calculate the current flowing through the armature at this point. 43 Amp. 33.33 Amp. 44.47 Amp. 29 Amp. 43 Amp. 33.33 Amp. 44.47 Amp. 29 Amp. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines For the speed control of polyphase squirrel cage induction motor, if frequency of operation is decreased with constant supply voltage V, starting torque Tst decreases constant V, Tst increases either of these None of these constant supply voltage V, starting torque Tst decreases constant V, Tst increases either of these None of these ANSWER DOWNLOAD EXAMIANS APP
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