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. 0.443. 0.512. 0.649. 0.573. 0.443. 0.512. 0.649. 0.573. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The direction of generated emf in the armature coil of a DC machine is 1. the same as that of the current in a generator 2. the same as that of the current in a motor 3. opposite to that of the current in a generator 4. opposite to that of the current in a motor From these, the correct answer is 2, 4 1, 4 2, 3 1, 3 2, 4 1, 4 2, 3 1, 3 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines An ideal synchronous motor has no starting torque because rotor winding is highly reactive. rotor is made up of salient poles. relative velocity between stator and rotor mmf’s is not zero. relative velocity between the stator and rotor mmf’s is zero. rotor winding is highly reactive. rotor is made up of salient poles. relative velocity between stator and rotor mmf’s is not zero. relative velocity between the stator and rotor mmf’s is zero. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 3 - Φ, 12 pole, 600 V, 50 Hz star connected IM has rotor resistance and stand still resistance of 0.03 Ω and 0.5 Ω respectively. The speed of maximum torque will be 240 rpm. 450 rpm. 470 rpm. 540 rpm. 240 rpm. 450 rpm. 470 rpm. 540 rpm. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The total core loss of a 400 V, 50 Hz transformer is 2400W, when it is supplied by 200 V, 25 Hz loss is 800W. Calculate eddy current loss and hysteresis loss? 800W, 1600W 1600W, 800W 1000W , 1400W 1400W, 1000W 800W, 1600W 1600W, 800W 1000W , 1400W 1400W, 1000W ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In case of a dc motor the ratio Eb / E is indicative of ratio of input to output voltage. efficiency. ratio of starting to running current. ratio of starting to running torque. ratio of input to output voltage. efficiency. ratio of starting to running current. ratio of starting to running torque. ANSWER DOWNLOAD EXAMIANS APP
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