Electrical Machines A commutator with a diameter of 50 cm rotating at 1000 rpm. For a brush width of 1.5 cm, find the time of commutation in ms. 0.649. 0.573. 0.443. 0.512. 0.649. 0.573. 0.443. 0.512. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines With the increase in speed of a DC motor back emf increases but line current falls. both back emf as well as line current fall. back emf falls and line current increases. both back emf as well as line current increase. back emf increases but line current falls. both back emf as well as line current fall. back emf falls and line current increases. both back emf as well as line current increase. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes : 2, 3 and 4 1, 2 and 4 1 and 3 1, 2, and 3 2, 3 and 4 1, 2 and 4 1 and 3 1, 2, and 3 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The oscillation in a synchronous motor can be damped out by running the motor on leading power factors. oscillation cannot be damped. providing damper bars in the rotor pole faces. maintaining constant excitation. running the motor on leading power factors. oscillation cannot be damped. providing damper bars in the rotor pole faces. maintaining constant excitation. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In a Dc generator the magnetic neutral axis coincide with geometrical neutral axis, when there is no load on the generator. the generator runs on designed speed. the generator runs on full load. the generator runs on overload. there is no load on the generator. the generator runs on designed speed. the generator runs on full load. the generator runs on overload. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Demagnetization effects which of the following? reduces the terminal voltage commutation reduction in main field flux both B and C reduces the terminal voltage commutation reduction in main field flux both B and C ANSWER DOWNLOAD EXAMIANS APP
EXAMIANS