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. 0.512. 0.573. 0.443. 0.649. 0.512. 0.573. 0.443. 0.649. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Consider a separately excited DC motor. If the field current is increased while the armature terminal voltage is held constant, then speed of the motor will remains same. none of these. Decrease.d increase. remains same. none of these. Decrease.d increase. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%. 72.5% 78.5% 82.5% 67.5% 72.5% 78.5% 82.5% 67.5% ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A compound dc generator is delivering full load current at a terminal voltage of 230 V. Its series-field winding gets short circuited. If its terminal voltage 1. becomes more than 230 V, it is overcompounded generator 2. becomes more than 230 V, it is differentially compounded generator 3. becomes less than 230 V, it is overcompounded generator 4. becomes less than 230 V, it is differentially compounded generator 5. becomes less than 230 V, it is level compounded generator From these, the correct answer is 1, 4 2,3 2, 3, 5 1, 4, 5 1, 4 2,3 2, 3, 5 1, 4, 5 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines DC Shunt Motor has disadvantage(s) of constant speed. not suitable for rapidly changing loads. less expensive. none of above. constant speed. not suitable for rapidly changing loads. less expensive. none of above. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines No load test on induction motor is conducted to find which of the following losses? Rotational loss Stator core loss All of these Stator copper loss Rotational loss Stator core loss All of these Stator copper loss ANSWER DOWNLOAD EXAMIANS APP
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