technical information

Electromagnetism

1.Magnet

A piece of solid substance which having a property of attracting a small pieces of material like iron, steel.
Below diagram of natural magnet is best example of these which attract small pieces of iron material.

There are two types of magnet:
1. Natural magnet
2. Electromagnet

2.Natural Magnet

Natural magnet having a natural property of attracting pieces of material like iron, steel etc.
In below diagram white pieces are iron material which attract by this magnet at the  N pole and S Pole.

Natural magnet

Natural magnet doesn't required in external energy create magnetic force like electromagnet.

3.Electromagnet

Electromagnet is form by passing electric current around certain material like iron.

Electromagnet

In above diagram ,when the current start flowing through this coil the metal act as a magnet.
 the magnetic action of the electromagnet present till electric current flows through the coil which ground around the solid material like iron. After stopping of electric current of the coil of electromagnet the magnetic energy of that iron is lost.

Properties of magnet

There are some important properties of magnet are as follows:

1. Magnet attract small pieces of iron.
2. Freely suspended magnet align itself in North-south direction

4.Magnetism

Whenever electric current flow through the conductor magnetic field produce surrounding that conductor. That means whenever the  electrons movement takes place in any conductor they will create the magnetism surrounding to that conductor.

5.Electromagnetic induction

When conductor cuts magnetic field EMF is get induced in that conductor and while connecting load across that coil or conductor current will start flow through this, that is called as electromagnetic induction.

6.Permeability

What the phenomenon of magnetism and electromagnetisme is basically depends on the property of material or property of medium. The medium through which magnetic flux is passed.

Permeability of any medium is of two types
1. absolute permeability
2. relative permeability

Absolute permeability

Absolute permeability of the material is defined as the ratio of magnetic flux density(B) to the magnetic field strength(H) which product that flux density.
The unit of absolute permeability is henry per meter  or Henry/meter.
Relative permeability of free space or vacuum is equals to 1.

Relative permeability

Relative permeability is defined as the ratio of flux densityB in particular medium produced by magnet to the flux density(B) in air or vacuum.

7.Electromotive force (EMF)

In electrical circuit electromotive force To flow of electron.
EMF is also called as volt which cause flow of electron.

8.Magnetomotive force(MMF)

The force responsible for flow flux is called as magnetomotive force (MMF).
MMF=N*I
Where,
N=number of turns of magnetizing c
I=current through a coil

9.Reluctance

statically induced EMF

In this section we will see about statically induced EMF. EMF means electromotive force.
The induced EMF is basically static induced EMF and dynamically induced EMF. In statically induced EMF, conductor is stationary that means the conductor is not moving. Also there is no any physical change in magnetic field.

Statically induced EMF

The Principle of statically induced EMF
The magnitude of current which produce magnetic field that are links with the conductor is change with respect to time.
To produce electromotive force statically its required to generate alternating flux  by alternating current source.
This alternating current produce alternating flux which pass through low reluctance path and link with another coil and because of this linkage EMF is induced in that coil.

There are different type of statically induced EMF
• Self induced EMF
• Mutual induced EMF

Fleming's rules

Fleming left hand rule

Faraday's law of electromagnetic induction

Faraday's first law of electromagnetic induction states that When change in magnetic flux links with the coil EMF is induced in that coil.

Faraday's law with change in magnetic flux

Due to that EMF, current will start flow through that coil through the load when load is connected on that coil.
Same as above fan a conductor cuts constant magnetic flux the EMF induced in that conductor because of motion of that conductor. The direction of induced EMF or current depends on direction of motion of that conductor as per the the Fleming right hand rule.

What is Faraday's 2nd Law?

Faraday's second law of electromagnetic induction states that magnitude of induced EMF in a coil is exactly equal to rate of change of flux linkage to the coil.

That means EMF induced in coil or conductor is depends on change in magnetic field, if the rate of change in magnetic field is low then EMF induced is also low and if the the rate of change in magnetic field is more than EMF induced in the coil is also more.

Related searches:

1.  Fleming left hand rule
2. Fleming right hand rule
3. Working principle of transformer

Working principle of transformer

Transformer core is made up of low reluctance material that is silicon steel and the winding of transformer is highly inductive.
 Transformer having Two electrical circuits link with common magnetic circuit. One is primary circuit and another is secondary circuit. When primary energizing with AC supply alternating flux produce which flow through magnetic path and links with secondary winding due to mutual induction. And the EMF induced in secondary winding according to Faraday law of electromagnetic induction. Open the secondary winding having a closed path current flow through this secondary winding.

Construction of transformer:

Transformer consists of two inductive coils links with common magnetic path that inductor coils namely primary coils and secondary coil.

Transformer core, winding view

 Core of the transformer is made up of steel material and that acts as a magnetic path of the flux. Core of the transformer made from number of silicon steel stampings laminated are comes together. Material of transformer core made up of low reluctance, high permeable material. To minimise the eddy current loss core made up of number of laminated steel stamping. Thickness of that steel stamping about 0.30mm for 50 Hertz.
On the basis of construction transformer divided into two different types core type and shell type.

 types of transformer on construction basis

Core type transformer

As shown in figure core type transformer having two windings that is primary winding and secondary winding which links with each other by magnetic path that is core. Coils used in transformer its cylindrical, circular, rectangular type can be used.
In small size core transformer rectangular shape of core used, in large core transformer cylindrical or rectangular type of core is used. Also stepped core can be used, per stepped core circular or cylindrical type of winding is used. Core stepping gives high space factor. Stepped core is one of the most commonly used for large type of core transformer due to that stepped core I2R loss also reduced. In large power transformer more number of stepped can be used.

Shell type transformer

In this type of transformer multilayer disc type winding mounted on the same limbs of transformer core which are insulated from each other and also the core of the transformer.
In this type of transformer most commonly used transformer is berry type of transformer. This type of transformer having some advantages over core type.

• More rigid construction
• Lesser weight and size per KVA is small
• Lower iron losses at higher flux density
• Lower manufacturing cost


Large size of transformer fully airtight chamber is used for tank in which insulating oil field which work as insulating medium between winding to winding and winding 2 to outer body of transformer, this will also act as a coolant of the transformer which circulate through to the plates that is cooling plates of the transformer.
On supply basis transformer is single phase transformer and three phase transformer
On the basis of voltage conversion there is step up transformer and step down transformer.

Related post:Three phase induction motor

Transformer body part

Transformer body parts

 material of core is highly permeable which is made from silicon steel. The core of transformer is made up from number of stamping which are laminated by insulating material like varnish, that’s stampings are laminated and width of that stampings is 0.35mm for 50 hertz frequency. Number of stampings attacks each other and the core transformer
Core is divided in number of stamping because of reducing eddy current losses because in solid material eddy current losses more so, hitting is more and that's why losses that is iron loss is more. Enlarge size of transformer more. For large size of power transformer stepped core is used.
In transformer iron loss is called as constant loss.

2.Winding:

 winding of the transformer is  of high conductive material that is copper, aluminium is used. This winding is different in safe for such as small power transformer having rectangular type coil is used. For large power transformer circular or rectangular type of.
The winding of the transformer we can say primary winding and secondary winding. If the transformer is step down transformer then the turns of the primary winding is greater than secondary winding and if the transformer is step up transformer then the turns of the primary winding less then turns of secondary winding. So, the number of turns in primary winding and secondary winding will decide the types of transformer that is step up transformer or step down transformer

3.Breather:

Breather is located at the conservator tank, by the pipe arrangement
Breather have mainly two works are there sucking air inside the tank and exhaust air to the atmosphere when will temperature decreases and increases, and II work of the brother is is to remove the moisture from the air which will entering in transformer tank at the time of sucking air from the atmosphere.
Breather consists of silica gel which is bluish in colour colour at the time of fresh condition and after absorption of moisture by aging affect its will pink in colour. the colour of the silica gel will decide the condition of silica gel. When it's become pink in colour its have to be replaced with new one.

In airtight transformer tank, breather is necessary. When the transformer oil is heated size of the transformer oil expanded due to expanding properties of molecule and it's require more space at the time of expanding oil air inside the tank is exhaust in atmosphere.
When the temperature of transformer oil decreases its previous state state so with this space required to the oil is also decreases. At that time breathing is necessary and atmosphere air inside the tank the tank of the transformer.

4.Explosion vent:

Explosion vent is a protective device used for transformer protection from the internal fault.
at the time of internal fault of the transformer gases inside the transformer tank increases suddenly that that gases have to be exhausted in the atmosphere quickly otherwise the tank of the transformer will damage, to avoiding this damage explosion vent is used to exhaust gases quickly.

 5.Transformerr oil:

Transformer oil is used for mainly two purposes first is cooling and second one is to provide insulation between winding to winding and winding to body of the transformer.
Transformer oil has good insulation property, power transformer strength of the transformer oil has to be check for every 6 month to avoid any damage.

6.Buchholz relay:

Buchholz relay is placed between the transformer tank and conservative tank.
Buchholz relay is a protective device use for the transformer protection from internal faults. When the internel faults occur in transformer, number of gases produced inside the type of transformer hydrogen nitrogen etc.
When the internal faults occur in transformer winding number of gases are produced that gases force the float of the buchholz relay proper sites that's why the alarm and tripping command send to the breaker of the transformer.

 7.Conservator tank:

Conservator tank is used at the top of the transformer tank. It is used for the storage of oil.
When the temperature of transformer oil increases it is expanded and it needs some space and that space provided by the conservator tank

8.Bushing:

Transformer has two windings HV winding and LV winding. HV winding connected to HV bushing and LV winding connected to LV bushing. The electrical connection of the transformer is given through that l b and HV bushing. Depending on the type of transformer that is step up or step down that is decided  the incoming supply of the transformer and the outgoing supply of the transformer connected to which winding.
In step up transformer primary winding is connected to low voltage side and secondary winding connected to high voltage side. In step down transformer primary winding connected to high voltage side and secondary winding connected to low voltage side.

Related post:Single phase inducton motor

9.cooling plates

Cooling plates are basicaly work as heat exchanger,which are exchanged heat of transformer oil and atmosphere air.oil cooling is done by using atmosphere air.

Three phase induction motor

Contents in this chapter

• Types of three phase induction motor 

1. Structure basis
2. Speed basis 

Working

Advantages

Disadvantages

Applications

Single phase induction motor

Types of single phase inducton motor

1.Split phase Induction motor

Working principle:

Working principle: