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. 0.573. 0.512. 0.649. 0.443. 0.573. 0.512. 0.649. 0.443. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In travelling cranes for hoisting and lowering which type of motor is preferred? Single phase induction motor. DC series motor. AC slip ring motor. Synchronous motor. Single phase induction motor. DC series motor. AC slip ring motor. Synchronous motor. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines For a DC Shunt Motor having armature resistance of 0.5 Ω and 2A armature current at no-load, when the armature current is changed to 20A at loaded condition the speed is 1000 r.p.m. What is the speed at no-load? 1037.5 r.p.m. 4575.4 r.p.m. 963.8 r.p.m. 1130 r.p.m. 1037.5 r.p.m. 4575.4 r.p.m. 963.8 r.p.m. 1130 r.p.m. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines When excitation is increased (over excitation), the synchronous generator operates at leading power factor. unity power factor. lagging power factor. any of the above. leading power factor. unity power factor. lagging power factor. any of the above. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines It is advisable to start a DC series motor with some load to Limit the current. Limit the speed. Limit the flux. Avoid sparking. Limit the current. Limit the speed. Limit the flux. Avoid sparking. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Consider the following statements regarding the speed control of dc motors : 1. ward-leonard method is suitable forconstant-torque drives 2. Ward-leonard method is suitable for constant-power drives 3. field-control method facilitates speed control below base speed 4. Armature-resistance control method is more efficient than ward-leanard method 5. Field-control method is suitable for constant-torque drives 6. Armature-resistance control method is suitable for constant-torque drives From these, the correct answer is 1, 2, 6 1, 2, 5 1, 4, 6 1, 3, 5 1, 2, 6 1, 2, 5 1, 4, 6 1, 3, 5 ANSWER DOWNLOAD EXAMIANS APP
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