Electrical Machines If an additional resistance is connected in series with a DC series motor operating at rated speed, the speed of the motor will Increase. Remain unaltered. Oscillate around the normal speed. Reduce. Increase. Remain unaltered. Oscillate around the normal speed. Reduce. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%. 960 RPM 940 RPM 920 RPM 970 RPM 960 RPM 940 RPM 920 RPM 970 RPM ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 230 V, 50 Hz, 4 pole single phase induction motor is rotating in the clockwise ( forward ) direction at a speed of 1425 rpm. If the rotor resistance at standstill is 7.8 Ω. Then the effective rotor resistance in the backward branch of the equivalent circuit will be 4 Ω. 10 Ω. 8 Ω. 2 Ω. 4 Ω. 10 Ω. 8 Ω. 2 Ω. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The counter (or back) emf in a dc machine is 1. the same as generated emf in a dc motor 2. proportional to field flux and armature speed 3. not the same as generated emf in a dc motor 4.inversely proportional to field flux 5. proportional to number of armature conductors 6. constant from no load to full load From these, the correct answer is 2, 4, 5, 6 3, 4, 5 1, 2, 5 2, 3, 6 2, 4, 5, 6 3, 4, 5 1, 2, 5 2, 3, 6 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The armature core of a DC machine is laminated to minimise mechanical loss hysteresis loss temperature rise eddy-current loss mechanical loss hysteresis loss temperature rise eddy-current loss ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In DC generators, the residual magnetism is of the order of 2.5 %. 15 %. 10 %. 20 %. 2.5 %. 15 %. 10 %. 20 %. ANSWER DOWNLOAD EXAMIANS APP
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