ELECTRICAL AND ELECTRONIC QUESTIONS ASKED IN INTERVIEW OF TRAINEE MARINE ENGINEER (TME)

  (1) Difference between Induction motor & Synchronisation motor

Ans:-

• In Synchronisation motor a separate dc source is required to excite the rotor but not in induction motors

(2) WHY INDUCTION MOTORS MOSTLY USED ON BOARD SHIP (about 95%)

Ans.  

(3) what are the types of three-phase induction motor starter and which is most used and why?

Ans:- Three types of starter, a.  Direct -online starter,    b. Star delta,.   C. Autotransformer 

Star - Delta starter method of starting three-phase induction motors is very common and widely used.

(4) what is the purpose of starter in DC motor?

Ans:- Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor's armature winding and restricts the current to an acceptable level.

(5) what is the condition of parallel operations of Alternated?

Ans.  a. The phase sequence of the busbar voltage and incoming machine voltage must be the same.

b. Busbar voltage & incoming m/c terminal voltage must be the same 

c. February must be the same 

d. Must be in phase 

(6) why  is the parallel operation of Alternators or Synchronisation is needed 

Ans:- 

• Several alternators can supply a bigger load than a single Alternator
• During the period of light load, one or more Alternators may be shut down & those remaining operate at or near full load.
• The machine is taken out for service
• When there is a breakdown of a generator, no interruptions of power supply.
• Operating cost reduced

  

(6) why brushless Alternator is now a day used?

Ans:- The need for slip rings & brushes is eliminated and the excitation is provided by a small Alternator.  The exciter, pilot exciter, and the alternator all are put on the same shaft thus dc current is supplied from an AVR.