Transformer
Electrician Trade Theory, Module-13
Transformer
⭕️ Show all Answers
Q1: Which type of transformer is used for high frequency application?
- Ring core transformer
- Ferrite core transformer
- Silicon steel core transformer
- Grain oriented core transformer
Q2: What is the relationship between primary voltage (E₁, V₁) and secondary voltage (E₂, V₂) in a ideal transformer?
- E₁ ≈ V₁ and E₂ ≈ V₂
- E₁ > V₁ and E₂ > V₂
- E₁ < V₁ and E₂ < V₂
- E₁ = V₂ and E₂ = V₁
Q3: 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
Q4: Which loss of transformer is determined by short circuit test?
- Copper loss
- Windage loss
- Hysteresis loss
- Eddy current loss
Q5: Calculate the voltage regulation in percentage of the transformer if the no load voltage is 240 volt and full load voltage is 220 volt?
- 7.20%
- 8.30%
- 8.71%
- 9.09%
Show Calculation
\[ \text{Voltage Regulation (%)}\]\[ = \frac{V_{\text{no-load}} - V_{\text{full-load}}}{V_{\text{full-load}}} \times 100 \] \[ = \frac{240 - 220}{220} \times 100 = \frac{20}{220} \times 100 = 9.09\% \]Q6: What is the purpose of using laminated core in transformer?
- Reduce copper loss
- Reduce hysteresis loss
- Reduce mechanical loss
- Reduce eddy current loss
Q7: 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
Q8: 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
Q9: 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
Q10: 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
Q11: 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
Q12: 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
Q13: What is the name of the part in power transformer?
- Breather
- Tap charger
- Explosion vent
- Buchholz relay
Q14: Which condition is absolutely essential for parallel operation of two transformers?
- Nature of load
- Type of cooling
- Phase sequence
- Class of insulation used
Q15: 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
Q16: What is the name of transformer?
- Air core transformer
- Iron core transformer
- Ring core transformer
- Ferrite core transformer
Q17: Which transformer is used to measure high voltage installations?
- Pulse transformers
- Ignition transformers
- Potential transformers
- Constant voltage transformers
Q18: How does the moisture is controlled in breather fitted on power transformers?
- Using silica gel
- Using transformer oil
- Using sodium chloride
- Using ammonium jelly
Q19: Which power loss is assessed by open-circuit test on transformer?
- Hysteresis loss only
- Eddy current loss only
- Copper loss
- Core loss
Q20: Which is determined by the crackle test of transformer oil?
- Acidity
- Moisture
- Viscosity
- Dielectric strength
Q21: Which material is used to make core of power transformer?
- Soft iron
- Rolled steel
- Copper alloy
- Cold rolled grain oriented
Q22: What is the name of transformer?
- Auto transformer
- Core type transformer
- Shell type transformer
- Audio frequency transformer
Q23: What is the purpose of providing explosion vent in a power transformer?
- Air releasing
- Heat releasing
- Pressure releasing
- Moisture releasing
Q24: 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
Q25: 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
Q26: Why distribution transformers are normally connected as primary in delta and secondary in star?
- To avoid over loading
- To maintain constant voltage
- To reduce transformer losses
- To easy distribution of 3 phase 4 wire system
Q27: Which type of emf is induced in an ideal two winding transformer?
- Self induced emf
- Mutually induced emf
- Statically induced emf
- Dynamically induced emi
Q28: How to determine copper loss in a transformer?
- Ratio test
- Impulse test
- Short circuit test
- Open circuit test
Q29: 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
Q30: 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
Q31: Which material is used in breather to prevent moisture entering in the transformer oil?
- Silica gel
- Sodium chloride
- Ammonium chloride
- Charcoal and salt mixture
Q32: What is the disadvantage of auto transformer?
- More losses
- Heavier in weight
- Poor voltage regulation
- Cannot isolate the secondary winding
Q33: Which cooling method is used in pole mounting distribution transformer?
- Air natural
- Oil natural air blast
- Oil forced air forced
- Oil natural air natural
Q34: What is the composition of steel and silicon steel in transformer core?
- Steel 97% and silicon 3%
- Steel 95% and silicon 5%
- Steel 93% and silicon 7%
- Steel 90% and silicon 10%
Q35: What is the purpose of tap changing in power transformers?
- Maintain primary voltage constant
- Change voltage ratio in distribution
- Maintain secondary voltage constant
- Load the transformer for maximum efficiency
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