# Building steel core out of stampings reduces eddy current loss because it

1.  increases core resistivity

2.  increases the effective length of eddy current paths thereby increasing effective resistance to the flow of eddy currents

3.  increases core permeability

4.  reduces the effective length of eddy current path, thereby reducing effective resistance to the flow of eddy currents

4

increases the effective length of eddy current paths thereby increasing effective resistance to the flow of eddy currents

Explanation :
No Explanation available for this question

# For fixed primary voltage how does the second terminal voltage of a transformer change if pf of inductive load is raised from 0.7 to 0.9 w load current remaining fixed

1.  No change in voltage

2.  Voltage decreases

3.  Voltage rises

4.  Voltage will rise, go through a maximum ai then decrease

4

Voltage rises

Explanation :
No Explanation available for this question

# Hysteresis losses are directly proportional to the

1.  square of frequency and flux density to the power 1.6.

2.  frequency and proportional to flux density to the power 1.6.

3.  the square of frequency and proportiona the square of flux density.

4.  frequency and proportional to flux density

4

frequency and proportional to flux density to the power 1.6.

Explanation :
No Explanation available for this question

# Power input to a transformer on no load at rated voltage comprises predominantly

1.  copper loss

2.  hysteresis loss

3.  core loss

4.  eddy current loss

4

core loss

Explanation :
No Explanation available for this question

# Which of the following tests must be performed on a transformer to determine its leakage reactance

1.  SC test only

2.  OC test only

3.  Both OC and SC tests

4.  test by an impedance bridge

4

Both OC and SC tests

Explanation :
No Explanation available for this question

# The applied voltage of a certain transformer is increase by 50% while the frequency is reduced to 50%. The maximum core flux density will

1.  become three times

2.  become 1.5 times

3.  become half

4.  remain the same

4

become three times

Explanation :
No Explanation available for this question

# For fixed primary voltage how does the secondary terminal voltage of a transformer change if the pf of capacitive load rises from 0,7 to 0.9 w load current remaining fixed

1.  no change in voltage

2.  voltage decreases

3.  voltage rises

4.  voltage decreases, goes through a minim and then rises

4

voltage decreases

Explanation :
No Explanation available for this question

# Transformer excited from a sinusoidal voltl source will draw a no-load current, which

1.  is sinusoidal and of the same frequency as the voltage source.

2.  comprises the fundamental frequency (same as that of the voltage source) and the peaking third harmonic.

3.  comprises the fundamental frequency and the depressing third harmonic.

4.   is sinusoidal of frequency three times that time of the voltage source

4

comprises the fundamental frequency (same as that of the voltage source) and the peaking third harmonic.

Explanation :
No Explanation available for this question

# A transformer on no-load is switched on to source of voltage. It will draw a current, which is

1.  the same as the steady-state magnetizing current

2.  several times the steady-state magnetizing current depending upon the initial state of th residual flux in the transformer core.

3.  several times the steady-state magnetizing current independent of the initial state of t!t residual flux in the transformer core.

4.  twice the steady-state magnetizing currofl provided the core has no residual flux

4

several times the steady-state magnetizing current depending upon the initial state of th residual flux in the transformer core.

Explanation :
No Explanation available for this question

# Auto-transformer is used in transmission and distribution

1.  when operator is not available

2.   when iron losses are to be reduced

3.  when efficiency considerations can be ignored

4.  when the transformation ratio is small

4