Electrical Transformers: Construction, Types, Connections, and Testing

Question 1

Which of the following is NOT a primary function of a transformer?

Accepted Answer

Power conversion

Answer

Voltage transformation

Answer

Current transformation

Answer

Isolation

Question 2

In a transformer, how do the primary and secondary coils interact during electromagnetic induction?

Accepted Answer

The primary coil creates a magnetic field that induces voltage in the secondary coil.

Answer

The secondary coil generates current that induces a magnetic field in the primary coil.

Answer

Both coils induce voltage and current simultaneously.

Question 3

What is the main reason for using transformer connections in electrical systems?

Accepted Answer

To efficiently transmit and distribute power over different distances and voltage levels

Answer

To only increase or decrease voltages for various applications

Answer

To separate circuits and provide protection from faults

Question 4

What is the primary function of a transformer?

Accepted Answer

To transfer electrical energy from one circuit to another, while isolating the circuits electrically.

Answer

To convert AC to DC

Answer

To increase the voltage of an electrical circuit

Question 5

What type of material is typically used to form the core of a transformer?

Accepted Answer

Laminated silicon steel

Answer

Copper

Answer

Plastic

Answer

Aluminum

Question 6

Which type of transformer is used to step down voltage?

Accepted Answer

Step-down transformer

Answer

Autotransformer

Answer

Isolation transformer

Answer

Step-up transformer

Question 7

What is the purpose of the oil in an oil-filled transformer?

Accepted Answer

To insulate and cool the transformer

Answer

To lubricate the transformer's moving parts

Answer

To protect the transformer from short circuits

Answer

To increase the transformer's efficiency

Question 8

What is the purpose of the windings on a transformer?

Accepted Answer

To carry the electrical current and create the magnetic flux in the core

Answer

To insulate the transformer

Answer

To protect the transformer from overloads

Answer

To cool the transformer

Question 9

What is the function of a transformer tap changer?

Accepted Answer

To adjust the transformer's voltage ratio, allowing for voltage regulation

Answer

To isolate the transformer from the power source

Answer

To cool the transformer

Answer

To protect the transformer from overloads

Question 10

What is the primary purpose of using a transformer in a power distribution system?

Accepted Answer

To reduce transmission losses and improve voltage regulation, enabling efficient power delivery

Answer

To increase the power factor of the system

Answer

To protect the system from short circuits

Question 11

Which material is primarily used in the core of a transformer to minimize energy losses?

Accepted Answer

Laminated silicon steel

Answer

Aluminum

Answer

Copper

Answer

Cast iron

Question 12

In an oil-filled transformer, the oil serves multiple purposes. Which of the following is NOT a function of the oil?

Accepted Answer

Lubrication

Answer

Insulation

Answer

Reducing noise

Answer

Cooling

Question 13

What is the primary effect of increasing the turns ratio in a transformer?

Accepted Answer

Increase in voltage and decrease in current

Answer

No change in voltage or current

Answer

Decrease in voltage and increase in current

Answer

Increase in both voltage and current

Question 14

Which type of transformer is specifically designed to prevent ground faults by isolating circuits?

Accepted Answer

Isolation transformer

Answer

Step-down transformer

Answer

Autotransformer

Answer

Step-up transformer

Question 15

What is the primary purpose of using a tap changer on a transformer?

Accepted Answer

Adjusting the turns ratio to regulate voltage

Answer

Isolating the transformer

Answer

Changing the polarity

Answer

Protecting the transformer from overloads

Question 16

Which electrical test is commonly used to determine the insulation resistance of a transformer?

Accepted Answer

Megger test

Answer

Winding resistance test

Answer

Ratio test

Answer

Polarity test

Question 17

When working with oil-filled transformers, which safety precaution is crucial to observe?

Accepted Answer

Wear appropriate protective clothing, including gloves

Answer

Ignore any warning labels

Answer

Use a ladder to reach the transformer

Answer

Work alone to minimize distractions

Question 18

What is a key disadvantage associated with using autotransformers?

Accepted Answer

Potential common mode voltage issues

Answer

Increased cost

Answer

Lower efficiency

Question 19

In a three-phase transformer, what is the primary function of a tertiary winding?

Accepted Answer

Providing a neutral connection

Answer

Reducing the current

Answer

Increasing the voltage

Answer

Isolating the primary from the secondary

Question 20

Which of the following are functions of transformer oil?

Accepted Answer

Cooling and insulation

Answer

Conduction and lubrication

Answer

Shielding and conduction

Answer

Lubrication and shielding

Question 21

What is the relationship between the turns ratio and voltage ratio in a transformer?

Accepted Answer

Directly proportional

Answer

Inversely proportional

Answer

Unrelated

Answer

Equal

Question 22

Which of the following is NOT a type of transformer connection?

Accepted Answer

Radial

Answer

Delta-star

Answer

Delta-delta

Answer

Star-star

Question 23

What is the primary purpose of a laminated core in a transformer?

Accepted Answer

Reduce eddy current losses

Answer

Provide insulation

Answer

Enhance mechanical strength

Answer

Increase magnetic permeability

Question 24

Which test is primarily used to determine the insulation integrity of a transformer?

Accepted Answer

Insulation resistance test

Answer

Polarization index test

Answer

Leakage inductance test

Answer

Turns ratio test

Question 25

What is the primary function of a conservator tank in a power transformer?

Accepted Answer

Maintain oil level and absorb moisture

Answer

Store spare oil

Answer

Provide electrical isolation

Answer

Cool the transformer windings

Question 26

What is the significance of a transformer's regulation?

Accepted Answer

Indicates voltage variation under load

Answer

Measures power output

Answer

Determines efficiency

Answer

Describes the transformer's reactance

Question 27

Which of the following is a typical application for isolation transformers?

Accepted Answer

Medical equipment

Answer

Power transmission

Answer

Distribution networks

Answer

Industrial machinery

Question 28

What is the main purpose of a step-down transformer?

Accepted Answer

Reduce voltage

Answer

Isolate circuits

Answer

Increase voltage

Answer

Change frequency

Question 29

Which fundamental principle governs the operation of transformers?

Accepted Answer

Electromagnetic induction

Answer

Transistor switching

Answer

Electrical resistance

Answer

Capacitive charging

Question 30

In a transformer, the primary voltage is primarily determined by:

Accepted Answer

Number of turns on the primary coil

Answer

Turns ratio of the transformer

Answer

Secondary voltage of the transformer

Answer

Power factor of the load

Question 31

Which specific type of transformer is utilized to electrically isolate circuits with different voltage levels?

Accepted Answer

Isolation transformer

Answer

Step-up transformer

Answer

Step-down transformer

Question 32

What is the primary reason for laminating the core of a transformer?

Accepted Answer

Minimize eddy current losses

Answer

Maximize magnetic field strength

Answer

Increase transformer efficiency beyond magnetic losses

Answer

Enhance insulation

Question 33

Step-up transformers are characterized by which combination of voltage and current changes?

Accepted Answer

Increased voltage, decreased current

Answer

No change in voltage or current

Answer

Decreased voltage, increased current

Answer

Increased current, decreased voltage

Question 34

What is the primary purpose of transformer oil?

Accepted Answer

Cooling and electrical insulation

Answer

Mechanical support

Answer

Transformer core lubrication

Answer

Electrical conduction

Question 35

In an ideal transformer, the ratio of primary to secondary voltage is equal to:

Accepted Answer

Turns ratio

Answer

Power ratio

Answer

Current ratio

Question 36

Which transformer connection is used to provide an isolated grounding point for a three-phase system?

Accepted Answer

Wye-wye with isolated neutral

Answer

Delta-delta

Answer

Wye-delta

Answer

Delta-wye

Question 37

The efficiency of a transformer is calculated by:

Accepted Answer

Output power / Input power

Answer

Turns ratio / Power ratio

Answer

Input power / Output power

Answer

Voltage ratio / Current ratio

Question 38

Which type of transformer is primarily used for power distribution in residential and commercial buildings?

Accepted Answer

Distribution transformer

Answer

Autotransformer

Answer

Power transformer

Answer

Instrument transformer

Question 39

The core of a transformer is laminated to:

Accepted Answer

Reduce eddy currents

Answer

Improve insulation

Answer

Lower winding resistance

Answer

Increase flux density

Question 40

Which test is used to verify the correct polarity of a transformer?

Accepted Answer

Polarity test

Answer

Ratio test

Answer

Insulation resistance test

Answer

Excitation test

Question 41

The impedance of a transformer is primarily determined by:

Accepted Answer

Number of turns and core material

Answer

Operating frequency

Answer

Core shape

Answer

Winding insulation

Question 42

Which of the following is NOT a type of transformer winding configuration?

Accepted Answer

Parallel-series

Answer

Zigzag

Answer

Wye

Answer

Star

Question 43

What is the primary purpose of laminating the core of a transformer?

Accepted Answer

Reduce eddy current losses

Answer

Provide a conducting path for the secondary current

Answer

Increase magnetic flux density

Answer

Insulate the primary and secondary windings from each other

Question 44

Which of the following is NOT a commonly used transformer connection method?

Accepted Answer

Open-star

Answer

Open-delta

Answer

Delta-delta

Answer

Star-star

Question 45

What is the main purpose of performing an insulation resistance test on a transformer?

Accepted Answer

Measure the resistance between the windings and the core

Answer

Determine the turns ratio of the transformer

Answer

Check the continuity of the windings

Question 46

Which transformer connection provides the highest possible voltage output?

Accepted Answer

Star-delta

Answer

Zigzag-star

Answer

Star-star

Answer

Delta-delta

Question 47

What is the optimal power factor for a transformer?

Accepted Answer

Unity

Answer

Leading

Answer

Zero

Answer

Lagging

Question 48

What is a primary function of the oil in an oil-filled transformer?

Accepted Answer

Insulate and cool the windings

Answer

Provide a low-resistance path for the current

Answer

Increase the magnetic flux density in the core

Question 49

Which of the following factors does NOT affect the efficiency of a transformer?

Accepted Answer

Ambient temperature

Answer

Copper losses

Answer

Core losses

Question 50

What is the primary function of a Buchholz relay in a transformer?

Accepted Answer

Detect abnormal gas pressure caused by internal faults

Answer

Control the voltage at the secondary terminals

Answer

Protect the transformer from overloading