Electrical Machine MCQs

A 3-phase,4-poe,400V, 50Hz squirrel-cage induction motor is operating at a slip of 0.02. The speed of the rotor flux in mechanical red/sec, sensed by a stationary observer, is closest to 

If a synchronous motor is running at a leading power factor, its excitation induced voltage is 

A separately excited DC generator supplies 150A to a 145V Dc grid. The generator is running at 800 RPM. The armature resistance of the generator is 0.1Ω. If the speed of the generator is increased to 1000 RPM, the current in amperes supplied by the generator to the DC grid is 

A 220V DC series motor runs drawing a current of 30A from the supply. Armature and field circuit resistance are 0.4Ω and 0.1Ω respectively. The load torque varies as the square of the speed. The flux in the motor may be taken as being proportional to the armature current. To reduce the speed of the motor by 50%, the resistance in ohms that should be added in series with the armature is 

A three-phase, three winding Δ/Δ/Υ( 1.1 kV/6.6 kV/ 400V) transformer is energized from AC mains at the 1.1 kV side. It supplies 900 kVA load at 0.8 power factor lag from the 6.6 kV winding and 300 kVA load at 0.6 power factor lag from the 400V winding. The RMS line current in ampere drawn by the 1.1 kV winding from the mains is