Electrical Machines A 230 V, 50 Hz, 4 pole single phase induction motor is rotating in the clockwise ( forward ) direction at a speed of 1425 rpm. If the rotor resistance at standstill is 7.8 Ω. Then the effective rotor resistance in the backward branch of the equivalent circuit will be 2 Ω. 8 Ω. 4 Ω. 10 Ω. 2 Ω. 8 Ω. 4 Ω. 10 Ω. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines What is the reason for stationary armature essential in alternators above 5 KVA? Operating cost is less. Collecting of large current is simple. Insulation requirement is less. All of these Operating cost is less. Collecting of large current is simple. Insulation requirement is less. All of these ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes : 2, 3 and 4 1, 2, and 3 1, 2 and 4 1 and 3 2, 3 and 4 1, 2, and 3 1, 2 and 4 1 and 3 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 100 KVA transformer is operating at 60 Hz, 240 V supply. The same transformer is operating at 50 Hz, 200 V supply. The new rating is 123.3 KVA 50 KVA 100 KVA 83.33 KVA 123.3 KVA 50 KVA 100 KVA 83.33 KVA ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines DC motors are stopped by opening line switches and not by forcing the handle of the motor starter back to OFF position. This is due to occurance of Heavy sparking at the first stud of starting resistance steps. None of these. Both of above. Heavy sparking at brushes. Heavy sparking at the first stud of starting resistance steps. None of these. Both of above. Heavy sparking at brushes. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 400 V, 50 Hz, 30 Hp, three phase IM is drawing 50 A current at 0.8 p.f lagging. The stator and rotor copper losses are 1.5 KW and 900 W respectively. The friction and windage losses are 1050 W and core losses are 1200 W. The air gap power of the motor will be 24.11 kW. 25 kW. 26.21 kW. 23.06 kW. 24.11 kW. 25 kW. 26.21 kW. 23.06 kW. ANSWER DOWNLOAD EXAMIANS APP
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