300 Important DC Motor MCQ Questions & Answers with Explanation | PDF Free Download
1.Ward Leonard system for controlling the speed of a dc motor is used where
- Athe speed in both the directions is required
- Bvery fine speed control over the whole range from zero to normal speed is required
- Cthe accuracy is speed control is required
- Dall of the above
2.Variation in speed by Ward Leonard control of dc motors occurs due to variation in
- Aarmature voltage
- Bfield
- Cfield diverter
- Darmature resistance
3.Ward Leonard control is basically a ___________ control method.
- AArmature voltage
- BField
- CField diverter
- DArmature resistance
4.Ward Leonard speed control method provides speed control
- Ain one direction only
- Bin both direction
- Cabove rated speed
- Dbelow rated speed
5.For very sensitive and wide speed control, the preferable control method is
- AField control
- BArmature control
- CMultiple voltage control
- DWard Leonard system
6.In Ward Leonard system, the lower limit of speed is imposed by
- AArmature resistance
- BField resistance
- CResidual magnetism of the generator
- DNone of the above
7.In Ward Leonard method of speed control, the direction of rotation of the motor is reversed usually by reversing the connections of the
- AGenerator field terminals
- BGenerator armature terminals
- CMotor armature terminals
- DMotor field terminals
8.The main disadvantages of the Ward Leonard system are
- AHigh initial cost
- BPoor overall efficiency
- CHigh maintenance cost
- DAll of the above
9.For a given torque, reducing diverter resistance of a dc series motor
- AIncreases its speed but armature current remains the same
- BIncreases its speed demanding more armature current decreases its speed demanding less armature current
- CDecreases its speed but armature current remains the same
- DDecreases speed but armature current remains the same
10.A dc series motor is operating at rated speed with rated excitation it has two resistance R1 and R2 connected across the field and the armature respectively. Speeds above the rated speed can be obtained by
- AIncreasing R1 only
- BReducing R2 only
- CReducing R1 and increasing R2
- DIncreasing R1 and R2
11.If an additional resistance is connected in series with a dc series motor operating at rated speed of the motor will
- AReduce
- BIncrease
- CRemain unaltered
- DOscillate around the normal speed
12.If a resistance is connected across the armature of a dc series motor, it speeds for a constant load torque will
- AIncrease
- BDecrease
- CRemain unaltered
- DBecome zero
13.Field diverter method of speed control of a dc series motor gives speeds above rated one due to reduction of
- AField current
- BArmature current
- CLine current
- DNone of these
14.The field diverter resistance for a dc series motor is of the order of
- A0.1 ohm
- B10 ohm
- C50 ohm
- D100 ohm
15.A dc series motor is running with a divertor connected across in field winding. If the divertor resistance is reduced then the speed of the motor will
- ADecrease
- BIncrease
- CBecome excessively high
- DRemain unaltered
16.Two dc series motors are connected in series and are driving the same mechanical load. If the motors are now connected in parallel the speed will become
- AOne fourth
- BHalf
- CDouble
- D4-times
17.In series-parallel control of dc series motor, the torque produced in series arrangement will be __________ of that in parallel arrangement.
- ADouble
- BFour times
- CHalf
- DOne fourth
18.The speed of a cumulative compound dc motor can be controlled by varying
- AArmature voltage
- BArmature resistance
- CShunt field resistance
- DAny of the above
19.The function of the field regulator in a dc compound motor is to
- ALimit the armature current
- BVary the armature resistance
- CControl the field current
- DNone of the above
20.The current drawn by a dc motor at starting is
- AZero
- BVery low
- CNormal
- DVery high