TRANSFORMERS

DJJ2022: ELECTRICAL TECHNOLOGYPUAN FARIDAH BT. SALLEH

PRESENTED BY:

• NURAIMI KHAIRINA BT YASMIN01DKM14F1138

• SITI ZULAIKA BT ISMAIL01DKM14F1130

• VINAASHA A/P BALAKRISHNAN01DKM14F1113

• SARAH BT MD AROFF01DKM14F1143

TRANSFORMER

• A transformer is a static device.• The word ‘transformer’ comes form the word

‘transform’.• Transformer is not an energy conversion

device, but it is device that changes AC electrical power at one voltage level into AC electrical power at another voltage level through the action of magnetic field but with a proportional increase or decrease in the current ratings., without a change in frequency.

• It can be either to step-up or step down.

TRANSFORMER CONSTRUCTION

If a load is connected to the secondary circuit, electric charge will flow in the secondary winding of the transformer and transfer energy from the primary circuit to the load connected in the secondary circuit.

WORKING PRINCIPLEThe main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. The working principle of the transformer can be understood from the figure below:

TYPE OF TRANSFORMER

CORE TYPE TRANSFORMER:-•The coils used for this transformer are form-wound and are of cylindrical type. • Applicable for small sized and large sized transformers.• In the small sized type, the core will be rectangular in shape and the coils used are cylindrical. •The figure below shows the large sized type. •In the case of circular cylindrical coils, they have a fair advantage of having good mechanical strength. •The cylindrical coils will have different layers and each layer will be insulated from the other with the help of materials like paper, cloth, macerate board and so on. •The general arrangement of the core-type transformer with respect to the core is shown below. Both low-voltage (LV) and high voltage (HV) windings are shown.

CORE-TYPE TRANSFORMER

SHELL-TYPE TRANSFORMER

• The coils are form-wound but are multi layer disc type usually wound in the form of pancakes.

• Paper is used to insulate the different layers of the multi-layer discs.

• The whole winding consists of discs stacked with insulation spaces between the coils.

• These insulation spaces form the horizontal cooling and insulating ducts.

• Transformer may have the shape of a simple rectangle or may also have a distributed form.

In shell-type transformers the core surrounds a considerable portion of the windings. The comparison is shown in

the figure below.

STEP-UP TRANSFORMER• In a step up transformer,

them number of turns in secondary

coil (Ns) is greater than that of primary coil( Np).

• The primary coil is made of a thick insulated copper wire ,while secondary coil of thin insulated wire. It converts low voltage at high current into high voltage at low current.

STEP-DOWN TRANSFORMER

• In a step-down transformer the number of turns in seondary coil (Ns) is less than that in primary coil(Np).

• In a step-down transformer ,the primary coil is made of a thin wire and the secondary coil of thick wire.It converts a high voltage at low current into a low voltage at high current

APPLICATIONS• A step-down

transformer is used for obtaining large current for electric welding.

• A step-down transformer is used in induction furnace for melting the metals.

• A step-up transformer is used for the production of X-rays.

• Transformers are used in voltage regulators and stabilised power supplies.

ENERGY LOSSES IN A TRANSFORMER

• TYPES OF ENERGY LOSSESi. Flux lossesii. Copper lossesiii. Iron losses iv. Hysteresis losses

•COPPER LOSS

Transformer Efficiency

• To check the performance of the device, by comparing the output with respect to the input.

• The higher the efficiency, the better the system.

Faraday’s Law

Faraday’s law states that:

Vs=Ns.dΦ/dt where VS is the instantaneous voltage. NS is the number of turns in the secondary coil.Since the same magnetic flux passes through

both the primary and secondary coils in an ideal transformer,the instantaneous voltage across the primary coil

Vp=Np.dΦ/dt

THANK YOU...