Electrical Machines To avoid formation of grooves in the commutator the brushes of same polarity should track each other. None of these brush position has no effect on the commutator grooving. the brushes of opposite polarity should track each other. the brushes of same polarity should track each other. None of these brush position has no effect on the commutator grooving. the brushes of opposite polarity should track each other. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary? It will be doubled. It will remain the same. It will be halved. It will becomes four times. It will be doubled. It will remain the same. It will be halved. It will becomes four times. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Which of the following methods of speed control is not affected through stator side? Change of supply voltage. Change of number of pole. Change of rotor resistance. Change of supply frequency. Change of supply voltage. Change of number of pole. Change of rotor resistance. Change of supply frequency. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If s is the slip and f is the supply frequency of an induction motor, the frequency of rotor current is given by sf / 2. sf. s2. f / s. sf / 2. sf. s2. f / s. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Copper brushes in DC machine are used None of these where high voltage and low current. where low voltage and high currents are involved. in both of above cases. None of these where high voltage and low current. where low voltage and high currents are involved. in both of above cases. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The polarity of a DC generator can be reversed by increasing field current. reversing field electric current as well as direction of rotation. reversing the field current. any of above. increasing field current. reversing field electric current as well as direction of rotation. reversing the field current. any of above. ANSWER DOWNLOAD EXAMIANS APP
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