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. 0.649. 0.443. 0.573. 0.512. 0.649. 0.443. 0.573. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In a synchronous machine, if the field flux axis is ahead of the armature field axis in the direction of rotation, the machine operating is synchronous motor. asynchronous motor. asynchronous generator. synchronous generator. synchronous motor. asynchronous motor. asynchronous generator. synchronous generator. 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 1, 2, 5 3, 4, 5 2, 3, 6 2, 4, 5, 6 1, 2, 5 3, 4, 5 2, 3, 6 2, 4, 5, 6 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The armature shaft must be able to withstand bending moment due to weight of the armature. twisting strains due to transmission of torque. All of these any unbalanced magnetic pull on the armature core. bending moment due to weight of the armature. twisting strains due to transmission of torque. All of these any unbalanced magnetic pull on the armature core. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 3-φ alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed, a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current Would be equal to If1/2. Woud be equal to 2If1. Cannot be predicted due to insufficient data. Would be equal to If1. Would be equal to If1/2. Woud be equal to 2If1. Cannot be predicted due to insufficient data. Would be equal to If1. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Field weakening method is also called as-----------? constant voltage control constant torque control constant power control constant current control constant voltage control constant torque control constant power control constant current control ANSWER DOWNLOAD EXAMIANS APP
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