FEE Flashcards - Transformers

Question 1

refers to one of the individual alternating current waveforms in a polyphase system.

Answer 1

Phase

Question 2

an electrical system that uses multiple alternating currents, each with a unique phase angle.

Answer 2

Polyphase System

Question 3

This system allows efficient generation, transmission, and utilization of power, reducing energy losses compared to single-phase systems.

Answer 3

Polyphase System

Question 4

The most common configuration of polyphase system

Answer 4

three-phase system

Question 5

a type of polyphase system where three AC currents are generated with identical magnitudes and frequencies but are separated by 120° phase angles.

Answer 5

three-phase system

Question 6

angular displacement between two sinusoidal waveforms of the same frequency

Answer 6

Phase Angle

Question 7

voltage measured between any two line conductors in a polyphase system.

Answer 7

Line Voltage

Question 8

Formula for Line Voltage

Answer 8

Vl = Vphase√3

Question 9

voltage measured across a single phase of the load or generator.

Answer 9

Phase Voltage

Question 10

In a star-connected system, it is the voltage between a phase conductor and the neutral point.

Answer 10

Phase Voltage

Question 11

one in which all the phase voltages or currents have equal magnitudes and are separated by equal phase angles.

Answer 11

Balanced System

Question 12

ensure efficient power transfer and reduce the risk of overheating in transmission lines or equipment.

Answer 12

Balanced System

Question 13

occurs when the magnitudes of the phase voltages or currents are not equal, or their phase angles deviate from the ideal values.

Answer 13

Unbalanced System

Question 14

a connection where one end of each phase winding is connected to a common neutral point

Answer 14

Star Connection

Question 15

It is widely used in power distribution.

Answer 15

Star Connection

Question 16

This connection allows the use of a neutral wire for grounding and provides multiple voltage levels

Answer 16

Star Connection

Question 17

A connection where the phase windings are connected end- to-end in a closed loop,

Answer 17

Delta Connection

Question 18

This configuration eliminates the need for a neutral wire and is common in industrial motor applications due to its ability to handle high currents and power.

Answer 18

Delta Connection

Question 19

the current flowing through a line conductor in a polyphase system.

Answer 19

Line Current

Question 20

Line Current Formula

Answer 20

Il = iphase√3

Question 21

the current flowing through a single phase of a load or generator.

Answer 21

Phase Current

Question 22

Its magnitude depends on the load and the system’s connection type (star or delta).

Answer 22

Phase Current

Question 23

a conductor in a star-connected system that provides a return path for current and helps stabilize voltage levels.

Answer 23

Neutral Wire

Question 24

It is particularly important in handling unbalanced loads.

Answer 24

Neutral Wire

Question 25

a static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.

Answer 25

Transformer

Question 26

It operates on the principle of Faraday's law of electromagnetic induction

Answer 26

Transformer

Question 27

states that a time-varying magnetic field induces an electromotive force (EMF) in a conductor.

Answer 27

Faraday's law of electromagnetic induction

Question 28

___ of a transformer is connected to the input (supply) side.

Answer 28

Primary winding

Question 29

When an alternating current flows through it, a magnetic field is created in the transformer core.

Answer 29

Primary winding

Question 30

connected to the output side of the transformer.

Answer 30

Secondary Winding

Question 31

The voltage induced in this winding is transferred to the load.

Answer 31

Secondary Winding

Question 32

the ratio of the number of turns in the primary winding to the number of turns in the secondary winding

Answer 32

Turns Ratio

Question 33

It determines the relationship between the input (primary) and output (secondary) voltages

Answer 33

Turns Ratio

Question 34

Turns Ratio Formula

Answer 34

Turns Ratio = Np/Ns = Vs/Vp

Question 35

a transformer that increases voltage from primary to secondary

Answer 35

Step-Up Transformer

Question 36

It has more turns in the secondary winding than the primary winding.

Answer 36

Step-Up Transformer

Question 37

a transformer that decreases voltage from primary to secondary

Answer 37

Step-Down Transformer

Question 38

It has fewer turns in the secondary winding than the primary winding.

Answer 38

Step-Down Transformer

Question 39

part of the transformer that provides a low-reluctance path for the magnetic flux.

Answer 39

Core (magnetic Core)

Question 40

The Core of a transformer is typically made of ___ to minimize energy losses due to eddy currents.

Answer 40

laminated silicon steel

Question 41

thin layers of steel used in the transformer core to reduce eddy current losses.

Answer 41

Laminations

Question 42

The ___ are insulated from each other to prevent circulating currents.

Answer 42

Lamination

Question 43

Special Types of Transformers

Answer 43

Auto-, Isolation, Three-phase, Current, Potential, and Toroidal Transformer

Question 44

a transformer with a single winding that acts as both the primary and secondary.

Answer 44

Auto-Transformer

Question 45

a transformer designed to isolate two circuits electrically while maintaining power transfer.

Answer 45

Isolation Transformer

Question 46

It has a 1:1 turns ratio and is often used for safety and noise reduction.

Answer 46

Isolation Transformer

Question 47

a transformer designed for three-phase power systems.

Answer 47

three-phase transformer

Question 48

It can consist of three separate single-phase transformers or a single unit with three sets of windings.

Answer 48

Three-phase transformer

Question 49

a type of transformer used to measure current.

Answer 49

Current Transformer

Question 50

It reduces high currents in power systems to a smaller, more manageable level for meters and relays.

Answer 50

Current Transformer

Question 51

a transformer used to measure voltage by stepping down high voltages to a lower level suitable for meters and relays.

Answer 51

Potential Transformer

Question 52

a transformer with a donut- shaped core that offers high efficiency and reduced electromagnetic interference (EMI).

Answer 52

Toroidal Transformer