Transformers - operating Flashcards
What is Electromagnetic induction?
Electromagnetic induction is when conductors cuts, or is cut by magnetic lines of a force(magnetic flux) a voltage is induced in the conductor.
How is an Electromagnetic induction function with magnetic
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
What does EMF stand for?
Electric and magnet force.
Define self- inductance?
self- inductance is when a change of a current produces a change of flux and therefore produces an induced EMF.
What is the unit of self-inductance?
Henry(H)
Define the formula for induced emf?
๐๐ง๐๐ฎ๐๐๐ ๐๐ฆ๐=โ๐.(๐๐โ๐๐)๐ญ๐ฏ๐จ๐ฅ๐ญ๐ฌ๐๐ง๐๐ฎ๐๐๐ ๐๐ฆ๐=โ๐.(๐๐โ๐๐)๐ญ๐ฏ๐จ๐ฅ๐ญ๐ฌ
L?
The value of inductance in henrys(H)
T?
Time in seconds (s)
I1 and I2?
Values of current.
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?
E
โL.(I2โI1)tโL.(I2โI1)
=
โ0.7ร(10โ2)/40 ร 10โ3
=
โ5.6 ร 10โ3/40ร10โ3
=
โ๐๐๐ ๐ฏ๐จ๐ฅ๐ญ๐ฌ
Define mutual inductance?
This is when the induced EMF in a circuit is due to a changing current in another circuit, ie a transformer.
What are the two types of practical transformer?
Primary and secondary
Define primary?
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.
Define secondary?
When alternating flux cuts to the conductor in secondary winding it induces a EMF into it secondary winding
What is the transformer equation?
๐๐(primary EMF)
๐๐(secondary EMF
=
๐๐(primary turns)
๐๐ (secondary turns)
๐จ๐ซ
๐๐๐๐ = ๐๐๐๐
Define the two distinct types of transformers?
Voltage transformer(VT) & Current transformer(CT)
These are collectively referred to as ______?
Instrument transformers
What connect the Voltage transformer?
voltmeter.
What connect to the current transformer
Ammeter?
What does a voltmeter measure?
High-voltage values
What does an ammeter measure?
High-current values.
How does the primary and secondary instruments work?
The high voltage and current to be measured is connected to the primary instrument transformer whilst the instrument itself are connected to the secondary.
What are the advantages of using an instrument transformer?
- The transformer isolates the instrument from main circuit
- 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
- Measuring instrument can be read easily in a remote, convenient positions connected by large leads to a instrument transformer.
How does Voltage transformer (VT) operate?
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.
What is the equation of voltage transformer?
VPVS=NPNS
How does current transformer (CT) operate?
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.
transformer already supply useful feature. what is it?
Isolation.
Define the ability of isolation?
Has the ability to couple one circuit to another without the uses of direct wire connections.
Define the functions of isolating transformers?
Isolating transformer donโt 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.
What will happen if you touch an earth rode or pole on an isolating transformer?
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.
What is the arrangement of a shaver socket?
A shaver socket provides 230 v for shavers but if a normal person where to touch it they wouldnโt get a electric shock.
What are the four types of supply transformer?
- Core single-phase
- core three-phase
- shell single-phase
- shell three-phase.