Dc Motor Interview Questions with Answers
Question: 1. What Is The Principle Of Operation Of A D.C Motor?
Answer:
The operation of a D.C Motor primarily based at the precept that once a present day carrying conductor is located in a magnetic area, the conductor stories a mechanical pressure. Basically, there’s no constructional distinction among a d.C. Motor and a d.C generator. The equal d.C. Machine may be run as a generator or motor.
Question: 2. What Is Back E.M.F Or Counter E.M.F?
Answer:
When the armature of a d.C. Motor rotates underneath the impact of the riding torque, the armature conductors flow thru the magnetic discipline and for this reason e.M.F. Is caused in them as in a generator. The induced e.M.F. Acts in contrary path to the carried out voltage V (Lenz’s law) and in known as returned or counter e.M.F Eb. It is always less than the applied voltage V, despite the fact that this difference is small when the motor is walking beneath everyday situations.
Electrical and Electronics Engineering Interview Questions
Question: three. What Is Speed Regulation?
Answer:
Speed law is the exchange in pace when the weight on the motor is reduced from rated price to zero. It is expressed as a percent of rated load speed.
Question: four. Why Series Motor Cannot Be Started On No-load?
Answer:
Series motor cannot be started out without load because of high starting torque. Series motor are used in Trains, Crane etc.
Question: 5. Which Type Of Motor Is Used In Trains, What Is The Rating Of Supply Used?
Answer:
Dc series is within the utilized in trains to get excessive starting torque while starting of the trains and the operating voltage is 1500v dc.
Electronic Circuits Interview Questions
Question: 6. Explain Different Methods Of Speed Control Of D.C Shunt Motors?
Answer:
Speed manipulate of a d.C shunt motor may be completed the use of:
Flux manipulate method ()
Armature manipulate method
Voltage manipulate approach
Question: 7. Explain Different Methods Of Speed Control Of D.C Series Motors?
Answer:
Speed manage of a d.C collection motor can be accomplished the usage of:
flux control method
Armature-resistance control control approach
Electrical Engineering Interview Questions
Question: 8. Why Is The Starting Current High In A Dc Motor (or) Why Do We Use A Starter?
Answer:
For DC motors, Voltage equation is
V=Eb-IaRa
Where V = Terminal voltage,
Eb = Back emf in Motor
Ia = Armature present day
Ra = Aramture resistance.
At beginning, Eb is zero. Therefore, V=IaRa, Ia = V/Ra, where Ra is very less like 0.01ohm.I.E, Ia will become pretty elevated. The excessive current will harm commutator and brushes and sooner or later blow out the fuses.
Question: nine. How Can You Reverse The Direction Of Rotation Of A D.C Motor?
Answer:
We can opposite the route of rotation of a D.C Motor by means of either reversing the sector present day or armature present day. If each the currents are reversed the motor will run in unique route.
Induction Motors Interview Questions
Question: 10. Why The Field Of A D.C Shunt Motor Should Not Be Open?
Answer:
The shunt motor will reap dangerously high velocity and may ruin itself.
Question: eleven. What Will Happen If The Direction Of Current At The Terminals Of A D.C Motor Is Reversed?
Answer:
The path of rotation of motor remains similar to cutting-edge in armature and subject.
Electrical Power System Interview Questions
Question: 12. What Happens When A D.C Motor Is Connected Across An A.C Supply?
Answer:
The motor will run however it might no longer bring equal load as it might on d.C supply.
More sparking on the brushes
Eddy currents can be excessive and could reason overheating and can sooner or later burn on a.C deliver
Electrical and Electronics Engineering Interview Questions
Question: 13. Mention The Methods For Starting An Induction Motor?
Answer:
DOL – direct on line starter
Star delta starter
Auto transformer starter
Resistance starter
Series reactor starter
Question: 14. What Are The Types Of Starters Used For Starting Of D.C Motors?
Answer:
There are two fundamental varieties of d.C. Motor starters viz., three-factor starter and 4-point starter. As we will see, the two types of starters differ handiest within the way in which the no-volt launch coil is connected.
Question: 15. What Are The Advantages Of Star-delta Starter With Induction Motor?
Answer:
The primary benefit of the use of the superstar delta starter is reduction of contemporary at some point of the starting of the motor. Starting contemporary is reduced to three-4 times of modern of Direct on line beginning. As the starting cutting-edge is reduced, the voltage drops during the starting of motor in structures are decreased.
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Question: sixteen. What Are The Different Tests Conducted On D.C Machines?
Answer:
Brake check
Swinburne’s take a look at or No-load take a look at
Regeneration test or Hopkinson’s take a look at
Retardation or Running down check
Question: 17. Why Is Swinburne’s Test Conducted?
Answer:
Swinburne’s test is performed at No-load circumstance to predetermine the efficiency at exceptional masses and to measure the losses separately.
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