Electrical Machines Satisfactory commutation of DC machine requires All of these brushes should smoothly run in the holders. smooth, concentric commutator properly undercut. brushes should be of proper grade and size. All of these brushes should smoothly run in the holders. smooth, concentric commutator properly undercut. brushes should be of proper grade and size. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The slight curvature at the lower end of the OCC of a self excited DC generator is due to high field resistance. magnetic inertia. high speed. residual flux. high field resistance. magnetic inertia. high speed. residual flux. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If in a sub – station there is one 132 / 33 kV transformer whose secondary is connected with primary of one 33 / 11 kV transformer, the total transformation ratio of the sub – station will be, 3. 4. 12. 7. 3. 4. 12. 7. ANSWER DOWNLOAD EXAMIANS APP
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 4 X 1012 Ω - cm at 27°C and 0.4 X 1012 1 X 1012 Ω - cm at 27°C and 0.1 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 4 X 1012 Ω - cm at 27°C and 0.4 X 1012 1 X 1012 Ω - cm at 27°C and 0.1 X 1012 2 X 1012 Ω - cm at 27°C and 0.2 X 1012 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines To avoid formation of grooves in the commutator the brushes of same polarity should track each other. brush position has no effect on the commutator grooving. the brushes of opposite polarity should track each other. None of these the brushes of same polarity should track each other. brush position has no effect on the commutator grooving. the brushes of opposite polarity should track each other. None of these ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated) changes to 1.5 times the original value changes to 0.5 times the original value remain the same as the original changes to three times the original value changes to 1.5 times the original value changes to 0.5 times the original value remain the same as the original changes to three times the original value ANSWER DOWNLOAD EXAMIANS APP
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