Ans: Moisture absorbing silicon gel or CaCl₂ is used to fill the breather which turns pink when it absorbs moisture . When fried again it gets its original form by removing its moisture contents.

Ans : It is a large diameter explosion vent pipe fitted on the top of the tank of transformer projecting upwards and incorporating diaphragms on the mouth of it.

Ans : If there is a large volume of gas formed within the tank due to short circuit fault in the winding the pressure is released from the transformer through the explosion vent pipe by rupturing the diaphragms mounted on the mouth of it.

Ans : The temperature of the hot oil be determined with the help of a thermometer by putting its bulb inside a low pocket meant for thermometer situated near the top of the transformer tank where the oil is hottest.

Ans : The temperature indicator is nothing but a dial type thermometer fitted in such a way that its bulb is immersed in the region where the transformer oil is hottest and the bulb is associated with a small encircled heating coil connected to the is so designed that the bulb temperature is increased by an amount equal to the greatest winding to oil temperature gradient and an appropriate value of temperature is indicated directly on the dial.

Ans: Bad cooling and overloading are the causes of temperature rise in a transformer .

Ans : The losses in a transformer are – (1) Core losses or iron or constant losses consisting of hysteresis and eddy current losses in the core and (2)Copper losses in the primary and secondary winding .

Ans: Since hysteresis is a kind of loss and affect the efficiency of the transformer, so it is always objectionable.

Ans: The hysteresis loss depends on (1)the quality and constituents of the iron core, (2) the frequency and (3) the flux density.

Ans: Hysteresis loss is more than eddy current loss in a transformer .

Ans : To reduce the hysteresis loss.

Ans: No, the core flux is always constant on every loads.

Ans : No load current produces core flux and supplies iron losses and copper loss on no load.

Ans : When a load is connected to the secondary side of a transformer the transformer is said to be on load and the current circulating through the secondary winding vai load is called the load current.

Ans : When the load current (I₂) flows through the secondary winding a counterbalancing current (I₁^,) is induced on the primary winding varying inversely to their respective turns . The total primary current on load (I₁) is equal to the vector sum of the primary counterbalancing current (I₁) and the no load current (I₀) which will be approximately equal to (I₁^,) as I₀ is practically very small.

Ans : Primary current increases with the increase in load current.

Ans : The equivalent circuit of the transformer means the simplified corresponding transformer circuit modeling the behavior of a real transformer which represents the primary circuit as well as the secondary circuit in one circuit with suitable parameters for easy calculation with the addition of a shunt circuit to account for no load current.

Ans : The approximate equivalent circuit of the transformer means a slight modification of the equivalent circuit by transferring the shunt circuit to the primary terminal with close approximation affecting very little change in the result.

Ans: Equivalent resistance referred to primary r₁^, =r₁+ (N₁/N₂)² r₂
Equivalent reactance referred to primary x₁^, =X₁ + (N₁/N₂ )² x₂
Equivalent resistance referred to secondary r₂^, = r₂ + (N₂/N₁ )² r₁
Equivalent reactance referred to secondary X₂^, = x₂+(N₂/N₁ )² x₁
Where, r₁ and r₂ are the primary and secondary resistances respectively. And x₁ and x₂ are the primary and secondary reactances respectively. N₁ and N₂ are the primary and secondary turns respectively.

Ans : 64 + j 117 ohms.

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