WorksheetsElectrical Machines-II Lab_Internal Test - 23-05-2020
Total questions: 20
Worksheet time: 17mins
By putting a controller resistor in series with rotor of dc shunt motor we can vary the speed
Up to normal value
Twice the normal value
Up to Half the normal value
None of the above
Three point starter is necessary to start dc motor
True
False
If the the resistance connected in series with the field coil of a dc shunt motor is increased the speed of the motor
Decreases
Increases
Remains constant
None of the Above
The function Commutator in the dc motor is
To Convert armature current from ac to dc
To produce pulsating torque in the armature
To convert armature current from dc to ac
None of the above
The main disadvantage of field control method of speed in dc shunt motor is
Speed will reach very high value
Large energy is wasted in field circuit
Commutation gets affected
All the above
Load test is suitable for which of the following motors
10kW motor
225kW Motor
545kW motor
All the above
In a dc shunt machine out of total losses majority of the losses are
Friction and Windage loss
Copper loss
Magnetic loss
None of the above
Losses in inter-pole winding are proportional to
Armtaure Current
Square of armature current
Field current
Square of field current
Eddy current losses in the dc motor are proportional to
Frequency and thickness of core
Square of frequency and thickness of core
frequency and square of thickness of core
square of frequency and square of thickness of core
In a DC series motor the Mechanical Losses will
Fairly remain constant
Vary with load variation
None of the above
In a Cage motor we use what type of starter to start the motor
Dual Online Starter
Star-Delta Starter
Rotor Resistance Starter
None of the above
The power factor of a Three phase induction motor when operating and load is completely released is in the range
0.44 to 0.85 lag
0.1 to 0.48 lag
0.58 to 0.88 lag
0.8 to 0.95 lag
Bangalore Metro Corporation Ltd. wanted to install new metro line from Majestic to BMSIT&M, it is searching for the type of motor to be chosen to drive the train, which motor would you suggest out of following motors
Slip Ring Induction Motor
Squirrel Cage Induction Motor
DC Shunt Motor
DC Series Motor
The Characteristic shown is of which motor
DC Shunt Motor
Induction Motor
DC Series Motor
Synchronous Motor
Which of the following statement is FALSE
DOL starter is used to start 3-ph induction motor because it is not self starting
Three point starter is used to add initial resistance in the motor armature circuit
Single phase induction motor is not self starting
Slip ring induction motor are having better starting torque
The range of slip for an Induction Machine is
0 to 1
-1 to 0
-1 to 1
0 to 0.5
Choose the correct statement -
In any electrical machine
Resistance is larger than reactance value
Reactance value is larger than resistance value
Both resistance and reactance values are almost equal
Reactance is square times the resistance value
If we use two wattmeters to measure the power consumed by the induction motor and incase if both wattmeters show equal reading but one negative, then the current lags voltage by an angle
45 degrees
90 degrees
0 degrees
None of the above
To reverse the direction of dc motor we have to
Reverse the direction of field connection
Reverse the direction of armature connection
Reverse either field or armature connections
Direction of rotation of motor can be given by
Fleming's Left Hand Rule
Fleming's Right Hand Rule
Faraday's Laws
Lenz's Law
