Electrical Machines A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to 0.5 p.u 0.75 p.u 0.125 p.u 0.25 p.u 0.5 p.u 0.75 p.u 0.125 p.u 0.25 p.u ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Capacitor start capacitor run provides high power factor only. high staring torque only. high staring torque and high power factor. none. high power factor only. high staring torque only. high staring torque and high power factor. none. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In a DC machine current and emf in armature are alternating. current and emf at the terminals are alternating. emf in armature conductors and at the terminals is alternating. current and emf in armature are unidirectional current and emf in armature are alternating. current and emf at the terminals are alternating. emf in armature conductors and at the terminals is alternating. current and emf in armature are unidirectional ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The principal of starting of 3 - Φ IM is similar to repulsion motor type starting. capacitor run IM. synchronous motor. transformer with short-circuited secondary. repulsion motor type starting. capacitor run IM. synchronous motor. transformer with short-circuited secondary. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The air gap between the yoke and armature is dc machine is kept very small All of these to avoid over heating. to avoid locking of the armature. to achieve a stronger magnetic field. All of these to avoid over heating. to avoid locking of the armature. to achieve a stronger magnetic field. 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%. 970 RPM 920 RPM 940 RPM 960 RPM 970 RPM 920 RPM 940 RPM 960 RPM ANSWER DOWNLOAD EXAMIANS APP
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