Natural air cooling is generally restricted for transformers up to

The bypass factor, in case of sensible cooling of air, is given by (where td₁ = Dry bulb temperature of air entering the cooling coil, td₂ = Dry bulb temperature of air leaving the cooling coil and td₃ = Dry bulb temperature of the cooling coil)

A

$$\frac{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

B

$$\frac{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}$$

C

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

D

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}{{{\text{t}}{{\text{d}}_1} - {\text{t}}{{\text{d}}_3}}}$$

After using for some time, big transformers get heated up. This is due to the fact that
1. current produces heat in the transformers.
2. hysteresis loss occurs in the transformers.
3. liquid used for cooling gets heated.
Select the correct answer:

A

Only 1

B

2 and 3

C

1 and 2

D

1, 2 and 3

The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil and h_A = Enthalpy of air at the end of dehumidification process)

A

$$\frac{{{{\text{h}}_{\text{A}}} - {{\text{h}}_2}}}{{{{\text{h}}_1} - {{\text{h}}_2}}}$$

B

$$\frac{{{{\text{h}}_2} - {{\text{h}}_{\text{A}}}}}{{{{\text{h}}_1} - {{\text{h}}_2}}}$$

C

$$\frac{{{{\text{h}}_1} - {{\text{h}}_2}}}{{{{\text{h}}_{\text{A}}} - {{\text{h}}_2}}}$$

D

$$\frac{{{{\text{h}}_{\text{A}}} - {{\text{h}}_1}}}{{{{\text{h}}_2} - {{\text{h}}_1}}}$$

Transformers with a capacity of up to _____ have a cooling radiator system with natural cooling

A

2 MVA

B

5 MVA

C

7.5 MVA

D

10 MVA

Simple air cooling system gives maximum cooling effect on ground surface whereas regeneration cooling system has more effect during high speeds.

A

True

B

False

Power transformers other than distribution transformers are generally designed to have maximum efficiency around ______

A

10% overload

B

Near full-load

C

Half-load

D

No-load

I. Pulse transformers use soft ferrites. II. The transformers used in the radio recievers use air core.

A

Only I is true

B

Only II is true

C

I and II are true

D

I and II are false

Compared to the natural cooling, how much of heat dissipation is increased by air blast cooling?

A

50-70%

B

60-70%

C

50-60%

D

40-60%

In MPFI-Air Induction System, the air cleaner, the air flow meter, the throttle body and the air valve supply a proper amount of air to the air intake chamber and intake manifold.

A

True

B

False

Suppose saturated polar air has an air temperature and dew point of -10o C, and unsaturated desert air has an air temperature of 35o C and a dew point of 10o C. The desert air contains ______ water vapour and has a ________ relative humidity than the polar air.

A

More, lower

B

More, higher

C

Less, lower

D

Less, higher

Natural air cooling is generally restricted for transformers up to

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