1. What is an electric drive?
a) A machine that converts electrical energy into kinetic energy
b) A machine that converts mechanical energy into electrical energy
c) A machine that converts electrical energy into mechanical energy
d) A machine that converts kinetic energy into electrical energy
Explanation: An electrical drive is a type of machine that converts electrical energy into mechanical energy while also providing electrical control over processes.
2. Which of the following is used to build a electric drive?
c) Control unit
d) All of the mentioned
Explanation: A source, a power modulator, a motor, a load, a sensing device, a control unit, and an input command can all be used to construct an electric drive.
3. Which of the following is/are components of an electric drive?
a) Control unit and Power Modulator
b) Electric Motor and Control System
c) Input Command
d) Sensing Device and Electric Motor
Explanation: Electric drive refers to the system or motor that is used to regulate motion. As a result, the electric motor and control system are essential components of an electric drive.
4. Which of the following is a function of electric drive?
a) Transport energy from the storage system to the wheels
b) Transport energy from the control system to the wheels
c) Transport fuel from the electric motor to the wheels
d) Transport fuel from the storage system to the wheels
Explanation: The electric drive system’s primary duty is to transport energy from the storage system to the wheels, which is utilised to overcome rolling resistance, air resistance, acceleration resistance, and climbing resistance. Mechanical energy is transformed to electrical energy and returned to the energy storage system upon braking.
5. What are electric drives?
a) Engines of 2-wheelers
d) Both a & c
Explanation: The drive system is utilised in a wide range of industrial and residential applications, including factories, transportation systems, textile mills, fans, pumps, motors, robotics, etc. Diesel or gasoline engines, gas or steam turbines, hydraulic motors, and electric motors all use drives as prime movers.
6. Which of the following exhibits linearly rising load torque characteristics?
a) Rolling Mills
b) Fan load
c) Separately excited dc generator connected to the resistive load
Explanation: Separately excited dc generator connected to the resistive load is an example of linearly rising load torque characteristics as the torque increases linearly with an increase in speed.
7. Type-A chopper is used for obtaining which type of mode?
a) Reverse motoring mode
b) Motoring mode
c) Reverse regenerative braking mode
d) Regenerative braking mode
Explanation: Only motoring mode is available in case of step-down chopper (Type-A chopper). Value of output voltage (Vo) is less than the input voltage (Vin) in case of step-down chopper.
8. Which of the following converter circuit operations will be unstable for a large duty cycle ratio?
a) Boost converter
b) Boost converter and Buck-Boost converter
c) Buck converter
d) Buck-Boost converter
Explanation: The output voltage of the buck converter and buck-boost converter are Vo=Vin ÷ (1-D) and Vo = D×Vin ÷ (1-D) respectively. When the value of the duty cycle tends to 1 output voltage tends to infinity.
9. Which of the following devices should be used as a switch for high power and high voltage application?
Explanation: Thyristor is used for high power applications but it has a limited frequency range and cannot be used at high frequencies. A thyristor is a unidirectional, bipolar and semi-controlled device.
10. Which of the following motor can be referred as a universal motor?
a) Permanent magnet motor
b) DC shunt motor
c) DC series motor
d) DC compound motor
Explanation: DC series motor can operate on DC and AC. It is a universal motor. Universal motors are those motors that can operate on both DC and AC. DC shunt motor can only operate on DC because of pulsating torque in AC.
11. What is the unit of the apparent or complex power?
Explanation: The apparent power in AC circuits is VI*. It is expressed in volt-amperes (VA). It consists of both active and reactive power. It is the vector sum of the real power and reactive power.
12. Which of the following device is NOT suitable for parallel operation?
Explanation: BJT has a negative temperature coefficient of resistance. If it is operated in parallel operation thermal run-away will take place and the device will damage.
13. The frame of an induction motor is made of _________
a) Silicon steel
c) Stainless steel
d) Cast iron
Explanation: The frame of an induction motor is made of cast iron. The power factor of an induction motor depends upon the air gap between stator and rotor.
14. Which of the following are used in preventing the hunting phenomenon in synchronous generators?
a) Distributed winding
b) Damper bars and short pitch chords
c) Short pitch chords
d) Damper bars
Explanation: Damper bars try to maintain synchronism between the rotating magnetic field and the rotor so they help in preventing hunting. It produces surges in the machine.
15. Which of the following core has linear characteristics?
a) CRGO core
b) Iron core
c) Air core
d) Steel core
Explanation: Air core coils have linear magnetization characteristics that are they do not saturate. Open circuit characteristics graph is linear in the case of synchronous machine.
16. Which one of the following methods would give a lower than the actual value of regulation of the alternator?
a) EMF method
b) ASA method
c) ZPF method
d) MMF method
Explanation: MMF method is an optimistic method of voltage regulation as it gives lower than the actual value of voltage regulation. MMF method will give the values that are lesser than the actual value.
17. The most suitable control-motor application is __________
a) AC one-phase induction motor
b) DC shunt motor
c) AC shunt motor
d) DC separately motor
Explanation: DC separately motor has definite full-load speed, so they don’t ‘run away’ when the load is suddenly thrown off provided the field circuit remains closed. The speed for any load within the operating range of the motor can be readily obtained.
18. What is the unit of the distance?
Explanation: Distance is the total length traced by the body. It is a scalar quantity. It is expressed in the meter. It is not a tensor quantity. It has no direction.
19. In the rotor voltage injection method, when an external voltage source is in phase with the main voltage then speed will ___________
b) First increases then decrease
d) Remain unchanged
Explanation: In the rotor injection method, when an external voltage is in phase with the main voltage net voltage increases and the value of slip decreases and the value of rotor speed increases.
20. Which of the following is the unit of displacement?
Explanation: Displacement is the difference between the final and initial point. It is a vector quantity. It is expressed in the meter. It is not a tensor quantity. It has direction.
21. Which of the following is the correct abbreviation of SCIM?
a) Solid cage induction motor
b) Square cage induction motor
c) Squirrel cage inverter motor
d) Squirrel cage induction motor
Explanation: SCIM stands for squirrel cage induction motor. SCIM rotor is made up of aluminum, copper bars. There are no armature conductors involved in it.
22. Which braking method is the best method for obtaining high braking torque?
b) Regenerative braking
c) Rheostatic braking
d) Dynamic braking
Explanation: Plugging is the best braking method among all braking techniques. In plugging the value of the armature current reverses and the mechanical energy is extracted. A very high braking torque is produced in case of plugging.
23. Which of the following is the correct abbreviation of IFOC?
a) Insight field oriented control
b) Indirect field oriented control
c) Inverter field oriented control
d) Isolated field oriented control
Explanation: IFOC stands for indirect field oriented control. DTC and IFOC are the techniques used for controlling the speed and torque of a 3-phase induction motor.
24. When 30 A current flows into the positive terminal of current source 8 V. Calculate the power delivered by the source.
a) -240 W
b) 356 W
c) -234 W
d) 243 W
Explanation: When the current enters the positive terminal of an element it will always absorb the power and when the current leaves the positive terminal it will deliver the power. Power delivered is -30×8=-240 W.
25. Which of the following is the correct abbreviation of NENO?
a) Neither even nor original
b) Neither even nor odd
c) Neither even nor orthogonal
d) Neither energy nor odd
Explanation: NENO stands for Neither even nor odd. The functions which are not the mirror image of the y-axis and nor symmetric about the origin are NENO functions.
26. DC shunt motors are used where the high _________ is required.
a) Breakdown torque
b) Starting torque
c) Maximum torque
d) Minimum torque
Explanation: DC series motors are used where the high starting torque is required. At starting the torque produced by DC series motor is very high.
27. Which starting method is the best method in Induction motor?
a) Reactance starting
b) Direct online starting
c) Star-Delta starting
d) Autotransformer starting
Explanation: The Star-Delta starting method is one of the best methods for the starting of the Induction motor. This method is cheaper and the line current in the star is 1÷3 times of in delta connection.
28. Which of the following are the classes of insulating material in electrical machines?
a) Γ, E, B, F, H, C
b) Γ, A, E, F, H, C
c) Γ, A, E, F, C
d) A, E, B, F, H, C
Explanation: Depending upon the temperature limits, insulating materials are classified into seven classes Γ, A, E, B, F, H, C. The insulation has the lowest temperature limit.
29. Which motor is preferred for Jaw crushers?
b) Belt slip ring IM
c) DC shunt motor
Explanation: Belt slip ring IM is preferred for the operation of Jaw crushers. A high starting is provided by the Belt ring IM. Slip rings are used to add external resistance.
30. Which of the following motor is a 1-Φ AC motor?
a) Shunt motor
b) Capacitor run
c) Series motor
d) Synchronous motor
Explanation: Capacitor run motor is a 1-Φ AC motor. The capacitor is used to provide a 90° phase difference between the currents of main and auxiliary winding.
31. Which of the following are the types of Stress?
a) Longitudinal stress, Shear stress
b) Longitudinal stress, Volume stress, Tangential stress
c) Longitudinal stress, Volume stress
d) Longitudinal stress, Lateral stress, Tangential stress
Explanation: There are three types of stress that are Longitudinal stress, Volume stress, Tangential or Shear stress. Stress is the ratio of restoring force and cross-section area.
32. Which of the following type of motor is used for milling and grinding operations?
a) Split phase
c) Reluctance motor
Explanation: Squirrel cage Induction motor is used for milling and grinding operations. SCIM has a rigid structure and high tolerating capability. It provides good running characteristics.
33. Which of the following test is used to determine the conditions where electric motors are being used?
Explanation: Thermography is used to detect heat patterns. It uses an Infrared rays camera. This test is used to determine the conditions where electric motors are being used.
34. Which of the following motor is used in recording instruments?
a) DC motor
b) Synchronous motor
c) Induction motor
d) Reluctance motor
Explanation: Reluctance motor is used in recording instruments. It is used for many constant speed applications. The starting torque of the motor depends upon the rotor position.
35. Which of the following is used to protect SCR from thermal conditions?
a) Voltage clamping device
b) Snubber circuit
c) Heat sink
d) Zener diode
Explanation: SCR is mounted on a heat sink. When temperature exceeded the rating of the SCR excess amount of heat is dissipated through the help of the heat sink.
36. Calculate the output frequency for the six-pulse converter if the supply frequency is 10 Hz.
a) 40 Hz
b) 50 Hz
c) 60 Hz
d) 70 Hz
Explanation: The output of a six-pulse converter consists of six pulses in one cycle. The output frequency of the six pulse converter is 6×supply frequency=6×10=60 Hz.
37. Which one of the following load is suitable for leading power factor load in Single phase Half-bridge inverter?
a) R-L-C underdamped
b) C load
c) L-C load
d) R-L-C overdamped
Explanation: R-L-C underdamped are leading power factor loads. They do not require any forced commutation technique. Anti-Parallel diodes help in the commutation process.
38. Which one of the following device is uncontrolled?
Explanation: Diode is uncontrolled, unidirectional power electronic device. When the voltage across the diode becomes positive it starts conduction otherwise remains off.
39. Which one of the element is used to make R load commutating?
Explanation: Capacitor is used to make the R load commutating. It is used in parallel with the resistive load.
40. Which of the relationship is correct in Permanent magnet DC motor?
a) T ∝ Ia
b) T2 ∝ Ia
c) T ∝ (Ia)0
d) T ∝ (Ia)2
Explanation: The value of flux remains constant in Permanent magnet DC motor. The torque in the PMMC motor is directly proportional to the armature current.
41. Calculate the active power in a 543 F capacitor.
a) 674 W
b) 56 W
c) 0 W
d) 364 W
Explanation: The capacitor is a linear element. It only absorbs reactive power and stores it in the form of oscillating energy. The voltage and current are 90° in phase in case of the capacitor so the angle between V & I is 90°. P=VIcos90°= 0 W. Current leads the voltage in case of the capacitor.
42. Calculate the active power in an 8.12 F capacitor.
a) 342 W
b) 452 W
c) 0 W
d) 77 W
Explanation: The capacitor is a linear element. It only absorbs reactive power and stores it in the form of oscillating energy. The voltage and current are 90° in phase in case of the capacitor so the angle between V & I is 90°. P=VIcos90° = 0 W.
43. Load interrupter operated at ________
a) Half of the full load
b) One-fourth of the full load
c) Full load
Explanation: Load interrupter is used to avoid overloading conditions. It separates the under-stressed area from the line. It operates at full load.
44. Current Chopping is most severe in which of the following?
a) Vacuum Circuit Breaker
b) Air Blast Circuit Breaker
c) Oil Circuit Breaker
d) Air Break Circuit Breaker
Explanation: Current chopping is most severe in the case of Air blast circuit breaker. Resistance switching is used to avoid the problem of current chopping.
45. When was the first train built?
Explanation: Richard Trevithick built the first train in 1804. It was a steam locomotive train that used to carry 10 tonnes of iron from one place to another.
46. Which of the following type of grounding is used to suppress the capacitive effect?
a) Reactance grounding
b) Peterson coil
c) Solid grounding
d) Resistance grounding
Explanation: Peterson coil or resonance grounding is used to suppress the capacitive effect. The frequency in resonance grounding is ω2 = 1÷(3LC).
47. Which of the following is the most severe type of fault?
Explanation: LLLG fault is the most severe type of fault. The order of severity is maximum for LLLG fault. LG fault is more severe at the generator terminals.
48. The value of area under a velocity-time graph is _________
Explanation: The value of the area under a velocity-time graph is displacement. The velocity is the ratio of displacement and time.
49. Which one of the following is the correct relationship?
Explanation: The value of the friction force is the product of the coefficient of friction and normal reaction. The correct value is F=μR.
50. Who is known as the Father of Indian Railways?
a) Lord Ripon
b) Lord Boult
c) Lord Hero
d) Lord Dalhousie
Explanation: Lord Dalhousie is known as the father of the Indian Railways. The first railway line connecting Bombay with Thane was laid in 1853.
Chapterwise Multiple Choice Questions on Electric Drives
- Dynamics of Electrical Drives
- Characteristics of DC & AC Motors
- Speed Control of Direct Current Motors & Induction Motors
- Braking of Electric Motors
- Braking of DC Motors & Induction Motors
- Rating and Heating of Motors
- Introduction to Solid State Controlled Drives
- Introduction to Solid-State Devices
- Introduction to Solid-State Switching Circuits
- Solar and Battery Powered Drives
- Traction Drives
- Electrical Drive Systems and Components
1. MCQ on Dynamics of Electric Drives
The section contains multiple choice questions and answers on loads types, speed quadrantal diagram, load torques that depends on path or position of load during motion, motor load combination dynamics, moment of inertia determination, electric drives steady state and transient stability.
2. Electric Drives Multiple Choice Questions on Characteristics of DC & AC Motors
The section contains Electric Drive questions and answers on dc motors basic relations and characteristics, dc shunt motors speed torque characteristics, modified characteristics applications, armature terminal voltage control, three phase induction and synchronous motors.
3. Electric Drives MCQ on Starting
The section contains Electric Drive MCQs on power supply starting effect, starting electric motors methods, acceleration time, energy relations and energy loss reduce methods during starting.
4. Electric Drives Multiple Choice Questions on Speed Control of Direct Current Motors & Induction Motors
The section contains Electric Drive multiple-choice questions and answers on shunt and series motor speed control, speed control basic principles, speed controlling using rotor resistance and inductance, rotor voltage injection, slip energy recovery, current source speed control, voltage/frequency control, speed controlling by adjusting stator voltage and supply frequency.
5. Electric Drives MCQ on Braking of Electric Motors
The section contains questions and answers on electric motors braking like regenerative braking, dynamic and countercurrent braking.
6. Electric Drives Multiple Choice Questions on Braking of DC Motors & Induction Motors
The section contains Electric Drive MCQs on dc shunt and series motors regenerative braking, dynamic braking of dc shunt and series motors, dc shunt motors countercurrent braking, 3-phase im regenerative braking and dynamic braking.
7. Electric Drives MCQ on Rating and Heating of Motors
The section contains Electric Drive multiple choice questions and answers on heating effects, loading conditions and duty classes, load inertia effect, electric motors determination, load equalisation and environmental factors.
8. Electric Drives Multiple Choice Questions on Introduction to Solid State Controlled Drives
The section contains Electric Drive questions and answers on dc and ac motor systems, switch-reluctance motor drives and brushless dc motors.
9. Electric Drives MCQ on Introduction to Solid-State Devices
The section contains Electric Drive MCQs on solid state devices transistors and thyristors, power electronic devices ratings, di/dt and dv/dt protections.
10. Electric Drives Multiple Choice Questions on Introduction to Solid-State Switching Circuits
The section contains Electric Drive multiple choice questions and answers on single phase, half-wave, ac/dc conversion for resistive loads and inductive loads without freewheeling diode, three phase, full-wave, ac/dc conversions, conversions like dc/dc and dc/ac conversion, three-phase energy recovery systems and current source inverter.
11. Electric Drives MCQ on Solar and Battery Powered Drives
The section contains Electric Drive questions and answers on solar panels, solar powered pump drives and vehicles.
12. Electric Drives Multiple Choice Questions on Traction Drives
The section contains Electric Drive MCQs on electric traction services, traction load nature, traction drives power factor and harmonics.
13. MCQ on Electric Drive Systems and Components
The section contains multiple choice questions and answers on electric drive systems, sequence operations and protection.
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Wish you the best in your endeavor to learn and master Electric Drives!