Transformers

31. When a given transformer is run at its rated voltage but reduced frequency, its

flux density remains unaffected
iron losses are reduced
core flux density is reduced
core flux density is increased

Detailed SolutionWhen a given transformer is run at its rated voltage but reduced frequency, its

32. Which of the following property is not necessarily desirable in the material for transformer core?

Mechanical strength
Low hysteresis loss
High thermal conductivity
High permeability

Detailed SolutionWhich of the following property is not necessarily desirable in the material for transformer core?

33. The ‘crawling’ in an induction motor is caused by

high loads
low voltage supply
improper design of machine
harmonics developed in the motor

Detailed SolutionThe ‘crawling’ in an induction motor is caused by

34. The term ‘cogging’ is associated with

three phase transformers
compound generators
series motors
induction motors

Detailed SolutionThe term ‘cogging’ is associated with

35. Short circuit test on transformers is conducted to determine

hysteresis losses
copper losses
core losses
eddy current losses

Detailed SolutionShort circuit test on transformers is conducted to determine

36. When the equivalent circuit diagram of doouble squirrelcage induction motor is constructed the two cages can be considered

in series
in parallel
in series-parallel
in parallel with stator

Detailed SolutionWhen the equivalent circuit diagram of doouble squirrelcage induction motor is constructed the two cages can be considered

37. An ideal transformer is one which has

no losses and magnetic leakage
interleaved primary and secondary windings
a common core for its primary and secondary windings
core of stainless steel and winding of pure copper metal

Detailed SolutionAn ideal transformer is one which has

38. Which of the following is the main advantage of an auto-transformer over a two winding transformer?

Hysteresis losses are reduced
Saving in winding material
Copper losses are negligible
Eddy losses are totally eliminated

Detailed SolutionWhich of the following is the main advantage of an auto-transformer over a two winding transformer?

39. While conducting short-circuit test on a transformer the following side is short circuited

High voltage side
Low voltage side
Primary side
Secondary side

Detailed SolutionWhile conducting short-circuit test on a transformer the following side is short circuited

40. Helical coils can be used on

low voltage side of high kVA transformers
high frequency transformers
high voltage side of small capacity transformers
high voltage side of high kVA rating transformers

Detailed SolutionHelical coils can be used on

Page 1Page 2Page 3Page 4Page 5
Test 1Test 2Test 3