Transformers - operating

Question 1

What is Electromagnetic induction?

Answer 1

Electromagnetic induction is when conductors cuts, or is cut by magnetic lines of a force(magnetic flux) a voltage is induced in the conductor.

Question 2

How is an Electromagnetic induction function with magnetic

Answer 2

If a conductor is held steady in a magnetic field or is moved in parallel to a magnetic field then no lines of force will be cut therefore no voltage is induce in the conductor

Question 3

What does EMF stand for?

Answer 3

Electric and magnet force.

Question 4

Define self- inductance?

Answer 4

self- inductance is when a change of a current produces a change of flux and therefore produces an induced EMF.

Question 5

What is the unit of self-inductance?

Answer 5

Henry(H)

Question 6

Define the formula for induced emf?

Answer 6

𝐈𝐧𝐝𝐮𝐜𝐞𝐝 𝐞𝐦𝐟=−𝐋.(𝐈𝟐−𝐈𝟏)𝐭𝐯𝐨𝐥𝐭𝐬𝐈𝐧𝐝𝐮𝐜𝐞𝐝 𝐞𝐦𝐟=−𝐋.(𝐈𝟐−𝐈𝟏)𝐭𝐯𝐨𝐥𝐭𝐬

Question 7

L?

Answer 7

The value of inductance in henrys(H)

Question 8

T?

Answer 8

Time in seconds (s)

Question 9

I1 and I2?

Answer 9

Values of current.

Question 10

If the current flowing through a coil of inductance of 0.7H increase from 2A TO 10A in 40 milliseconds, calculate the average value of induced EMF?

Answer 10

E

−L.(I2−I1)t−L.(I2−I1)
=
−0.7×(10−2)/40 × 10−3
=
−5.6 × 10−3/40×10−3
=
−𝟏𝟒𝟎 𝐯𝐨𝐥𝐭𝐬

Question 11

Define mutual inductance?

Answer 11

This is when the induced EMF in a circuit is due to a changing current in another circuit, ie a transformer.

Question 12

What are the two types of practical transformer?

Answer 12

Primary and secondary

Question 13

Define primary?

Answer 13

Primary are winding which produce an a.c current through the primary winding and this produces a flux in the iron core that is also alternating.

Question 14

Define secondary?

Answer 14

When alternating flux cuts to the conductor in secondary winding it induces a EMF into it secondary winding

Question 15

What is the transformer equation?

Answer 15

𝐕𝐏(primary EMF)
𝐕𝐒(secondary EMF
=
𝐍𝐏(primary turns)
𝐍𝐒 (secondary turns)
𝐨𝐫
𝐍𝐏𝐍𝐒 = 𝐕𝐏𝐕𝐒

Question 16

Define the two distinct types of transformers?

Answer 16

Voltage transformer(VT) & Current transformer(CT)

Question 17

These are collectively referred to as ______?

Answer 17

Instrument transformers

Question 18

What connect the Voltage transformer?

Answer 18

voltmeter.

Question 19

What connect to the current transformer

Answer 19

Ammeter?

Question 20

What does a voltmeter measure?

Answer 20

High-voltage values

Question 21

What does an ammeter measure?

Answer 21

High-current values.

Question 22

How does the primary and secondary instruments work?

Answer 22

The high voltage and current to be measured is connected to the primary instrument transformer whilst the instrument itself are connected to the secondary.

Question 23

What are the advantages of using an instrument transformer?

Answer 23

1. The transformer isolates the instrument from main circuit
2. The secondary side of the instrument will have lower voltage which can simplify the insulation of the measuring instrument which will make it safe to work with
3. Measuring instrument can be read easily in a remote, convenient positions connected by large leads to a instrument transformer.

Question 24

How does Voltage transformer (VT) operate?

Answer 24

Voltage transformer operate as step down transformer and is constructed very similar to a basic power transformer. Meanwhile the secondary winding is connected to the voltmeter or the volt coil of the wattmeter.

Question 25

What is the equation of voltage transformer?

Answer 25

VPVS=NPNS

Question 26

How does current transformer (CT) operate?

Answer 26

Current transformer operate has the same principle as but is slightly different from a basic power transformer. Many of the secondary winding more then the primary winding have very few turns. Which means it the opposite of VT. Secondary is connected to ammeters or current coil of the wattmeter.

Question 27

transformer already supply useful feature. what is it?

Answer 27

Isolation.

Question 28

Define the ability of isolation?

Answer 28

Has the ability to couple one circuit to another without the uses of direct wire connections.

Question 29

Define the functions of isolating transformers?

Answer 29

Isolating transformer don’t not usually step up or step down voltage and the secondary is the same as the primary, The neutral of a supply system in connected to the earth on the substation this means if you touch line and earth you will get the exact same shock as if a line and neutral.

Question 30

What will happen if you touch an earth rode or pole on an isolating transformer?

Answer 30

If you touch either or you will not get a electric shock however if you touch them at the exact same time that when you will get an electric shock.

Question 31

What is the arrangement of a shaver socket?

Answer 31

A shaver socket provides 230 v for shavers but if a normal person where to touch it they wouldn’t get a electric shock.

Question 32

What are the four types of supply transformer?

Answer 32

1. Core single-phase 2. core three-phase 3. shell single-phase 4. shell three-phase.