The torque developed by a 3-phase induction motor least depends on__________?
A. rotor current
B. rotor power factor
C. rotor e.m.f.
D. shaft diameter
Polyphase Induction Motors
Which motor is preferred for use in mines where explosive gases exist ?
Which motor is preferred for use in mines where explosive gases exist ?
A. Air motor
B. Induction motor
C. D.C. shunt motor
D. Synchronous motor
Lubricant used for ball bearing is usually___________?
Lubricant used for ball bearing is usually___________?
A. graphite
B. grease
C. mineral oil
D. molasses
The circle diagram for an induction motor cannot be used to determine____________?
The circle diagram for an induction motor cannot be used to determine____________?
A. efficiency
B. power factor
C. frequency
D. output
Blocked rotor test on induction motors is used to find out?
Blocked rotor test on induction motors is used to find out?
A. leakage reactance
B. power factor on short circuit
C. short-circuit current under rated voltage
D. all of the above
The complete circle diagram of induetion motor can be drawn with the help of data found from__________?
The complete circle diagram of induetion motor can be drawn with the help of data found from__________?
A. noload test
B. blocked rotor test
C. stator resistance test
D. all of the above
In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?
In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?
A. to reduce the magnetic hum and locking tendency of the rotor
B. to increase the tensile strength of the rotor bars
C. to ensure easy fabrication
D. none of the above
The torque of a rotor in an induction motor under running condition is maximum__________?
The torque of a rotor in an induction motor under running condition is maximum__________?
A. at the unit value of slip
B. at the zero value of slip
C. at the value of the slip which makes rotor reactance per phase equal to the resistance per phase
D. at the value of the slip which makes the rotor reactance half of the rotor
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
A. The slip of the motor will be 5%
B. The rotor will not run
C. The rotor will run at very high speed
D. The torque produced will be very large
The stating torque of the slip ring induction motor can be increased by adding__________?
The stating torque of the slip ring induction motor can be increased by adding__________?
A. external inductance to the rotor
B. external resistance to the rotor
C. external capacitance to the rotor
D. both resistance and inductance to rotor