TRANSFORMER

Which type of transformer is used for high frequency application? Ring core transformer Ferrite core transformer Silicon steel core transformer Grain oriented core transformer

What is the function of conservator in transformer? Prevents the moisture entry Transfers the heat to atmosphere Allows to release internal pressure Allows expansion of oil level due to load variation

Which loss of transformer is determined by short circuit test? Copper loss Windage loss Hysteresis loss Eddy current loss

Calculate the voltage regulation in percentage of the transformer if the no load voltage is 240 volt and full load voltage is 220 volt? 7.2 % 8.3 % 8.71% 9.09%

What is the purpose of using laminated core in transformer? Reduce copper loss Reduce hysteresis loss Reduce mechanical loss Reduce eddy current loss

What is the cooling method of transformer?

Oil natural cooling Oil natural air forced cooling Oil forced air forced cooling Oil natural water forced cooling

What is the condition for obtaining maximum efficiency from transformer? Copper loss > Iron loss Copper loss < Iron loss Copper loss = Iron loss Copper loss =Eddy current loss

What is the function of top float switch of buchholz relay in transformer? Activate in moisture presence Activate at overloading condition Activate at open circuit condition Activate at high temperature condition

Why the core of current transformer is having low reactance and low core losses? To minimise the burden To maintain constant output To prevent high static shield To minimise the error in reading

How the error in reading of a potential transformer can be reduced? Using thin laminated core Providing long magnetic path Using high flux density material Providing good quality core material

Why the load is disconnected before the OFF load tap changing operation? To disconnect the tappings from neutral point To disconnect the moving contact of the diverter To avoid heavy sparking at the contact points To provide an electrical isolation for the windings

Which condition is absolutely essential for parallel operation of two transformers? Nature of load Type of cooling Phase sequence Class of insulation used

Which construction technique is used to reduce copper loss in larger transformers? Use of laminated core By reducing core thickness By using grain oriented core Use stepped core arrangement

Which transformer is used to measure high voltage installations? Pulse transformers Ignition transformers Potential transformers Constant voltage transformers

How does the moisture is controlled in breather fitted on power transformers? Using silica gel Using transformer oil Using sodium chloride Using ammonium jelly

Which power loss is assessed by open-circuit test on transformer? Hysteresis loss only Eddy current loss only Copper loss Core loss

Which is determined by the crackle test of transformer oil? Acidity Moisture Viscosity Dielectric strength

Which material is used to make core of power transformer? Soft iron Rolled steel Copper alloy Cold rolled grain oriented

What is the name of transformer?

Auto transformer Core type transformer Shell type transformer Audio frequency transformer

What is the purpose of providing explosion vent in a power transformer? Air releasing Heat releasing Pressure releasing Moisture releasing

What is the function of buchholz relay in power transformer? Protection from high temperature Protection from moisture entering in oil Protection from pressure loading in tank Protection from both overloading and short circuit

Why primary of potential transformer is wound with thin wire and large number of turns? To offer high inductance To obtain required voltage ratio To regulate the primary current To stabilise input and output voltage

Why distribution transformers are normally connected as primary in delta and secondary in star? To avoid overloading To maintain constant voltage To reduce transformer losses To easy distribution of 3 phase 4 wire system

Which type of emf is induced in an ideal two winding transformer? Self induced emf Mutually induced emf Statically induced emf Dynamically induced emf

How to determine copper loss in a transformer? Ratio test Impulse test Short circuit test Open circuit test

Why ferrite core is used in radio receivers? To reduce the constant losses To reduce electric interference To increase the quality of sound To increase the efficiency of receivers

What is the advantage of stepped core arrangement in larger transformers? Minimizes copper use Reduces hysteresis loss Reduces eddy current loss Reduces the space for core

Which material is used in breather to prevent moisture entering in the transformer oil? Silica gel Sodium chloride Ammonium chloride Charcoal and salt mixture

What is the disadvantage of auto transformer? More losses Heavier in weight Poor voltage regulation Cannot isolate the secondary winding

Which cooling method is used in pole mounting distribution transformer? Air natural Oil natural air blast Oil forced air forced Oil natural air natural

What is the composition of steel and silicon steel in transformer core? Steel 90% and silicon 10% Steel 97% and silicon 3% Steel 95% and silicon 5% Steel 93% and silicon 7%

What is the purpose of tap changing in power transformers? Change voltage ratio in distribution Change voltage ratio in distribution Maintain secondary voltage constant Load the transformer for maximum efficiency