WorksheetsDC Drives
Total questions: 34
Worksheet time: 26mins
Drives are nothing but
power electronics
motors
controllers
combination of all
The consideration involved in the selection of the type of electric drive for a particular application depends upon
Speed control range and its nature
Starting Nature
Environmental condition
All of the above
which of the braking system is used in industries
Plugging braking
Dynamic braking
Regenerative braking.
What will happen if DC shunt motor is connected across AC supply?
Will run at normal speed
Will not run
Will Run at lower speed
Burn due to heat produced in the field winding
What will happen if the back emf of a DC motor vanishes suddenly?
The motor will stop
The motor will continue to run
The armature may burn
The motor will run noisy
What will happen, with the increase in speed of a DC motor?
Back emf increase but line current falls.
Back emf falls and line current increase.
Both back emf as well as line current increase.
Both back emf as well as line current fall.
Which part will surely tell that given motor is DC motor and not an AC type?
Winding
Shaft
Commutator
Stator
Direction of rotation of motor is determined by
Faraday’s law
Lenz’s law
Coulomb’s law
Fleming’s left-hand rule
Direction of rotation of motor is determined by ________
Faraday’s law
Lenz’s law
Coulomb’s law
Fleming’s left-hand rule
In which of the following application DC series motor is used?
Centrifugal Pump
Motor Operation in DC and AC
Water pump drive
Starter for car
In DC motor, which of the following part can sustain the maximum temperature rise?
Field winding
Commutator
Slip rings
Armature winding
These days D.C. motors are widely used in
pumping sets
air compressors
electric traction
machine shops
Which power is mentioned on a name plate of a motor?
Gross power
Power drawn in kVA
Power drawn in kW
Output power available at the shaft
Which of the following quantity will decrease if supply voltage is increased?
Starting torque
Operating speed
Full-load current
Cannot be determined
The speed of a D.C. shunt motor more than its full-load speed can be obtained by
Decreasing the field current
Increasing the field current
Decreasing the armature current
Increasing the armature current
Which D.C. motor has got maximum self loading property?
Series motor
Shunt motor
Cumulatively compounded ‘motor
Differentially compounded motor
Identify the speed torque characteristics of a dc series motor.
Which of the following is the best braking method?
Friction
Electromechanical action
Eddy-currents
Electric braking
DC motor is still widely used in tractions due to its excellent braking properties.
True
False
Which of the following is not the method of electrical braking?
Plugging or counter-current
Dynamic or rheostatic
Regenerative
Eddy current
Electrical braking of any variety becomes less effective as ________________
Speed increases
Speed decreases
Independent of speed
Depends on supply voltage
Plugging is applied in a motor, if we don’t make the switch OFF what will happen?
Motor will come to rest as a result of plugging
Motor will come to rest and will start rotating in another direction
Motor will burn
Which of the following is dynamic braking?
Reversal of field connections
Reversal of armature connections
Addition of equal and opposite field
Removal of armature circuit from current machine circuit
In dynamic braking, when braking is applied system acts as ___________
Freely running machine
Motor with slow speed
Generator
Motor with same speed in opposite direction
If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
Regenerative
Dynamic
Plugging
During rheostat braking of D.C. series motors
Motor run as a generator
motor run in the reverse direction
motor run at reduced speed
The current drawn by the armature of D.C. motor is directly proportional to
Torque required
Speed of the motor
voltage across the terminal
For constant torque drive which speed control method is preferred ?
Field control
Armature voltage control
Shunt armature control
Mechanical loading system
Which of the following motor has the poorest speed
regulation ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor
How is it possible to achieve Regenerative method of braking?
back e.m.f. is less than the applied voltage
back e.m.f. is equal to the applied voltage
back e.m.f. of rotor is more than the applied voltage
If there is an increase in temperature, what will be the effect of the speed in case of series and shunt motor?
Increase, decrease
Decrease, increase
Increase, increase
Decrease, decrease
On which of the following factors does the sensitivity of a close loop system to gain changes and load disturbances depend ?
Frequency
Voltage
Position
All the above
What is the function of low pass filter in phase-locked loop?
Improves low frequency noise
Removes high frequency noise
Tracks the voltage changes
Changes the input frequency
At what range the PLL can maintain the lock in the circuit?
Lock in range
Input range
Feedback loop range
