■ The transformer is a static device which is used to transfer electrical
energy from one ac circuit to another ac circuit.
■ Input to a transformer and output from a transformer both are
alternating quantities (AC).
■ Electrical energy is generated and transmitted at an extremely high
voltages. The voltage is to be then reduced to a lower value for its
domestic and industrial use.
■ This is done by using a transformer.
3. ■ The power transmission system using transformers is
shown in figure.
■ When the transformer changes the voltage level, it
changes the current level also.
5. ■ The primary winding is connected to the single-phase ac
supply, an current starts flowing through it.
■ The ac primary current produces an alternating flux (Ф) in the core.
■ Most of this changing flux gets linked with the secondary winding
through the core.
6. ■ The varying flux will induce voltage into the secondary
winding according to the faraday’s laws of electromagnetic
■ Voltage level change but frequency i.e. time period remains
■ There is no electrical contact between the two winding, an
electrical energy gets transferred from primary to the
7. ■ A simple transformer consists of two electrical
conductors called the primary winding and the
■ Energy is coupled between the windings by the
time varying magnetic flux that passes through(
links) both primary and secondary windings.
■ For the simple construction of a transformer, you must need two coils
having mutual inductance and a laminated steel core.
■ The two coils are insulated from each other and from the steel core.
■ The device will also need some suitable container for the assembled core
and windings, a medium with which the core and its windings from its
container can be insulated.
9. ■ In order to insulate and to bring out the terminals of the winding
from the tank, apt bushings that are made from either porcelain or
capacitor type must be used.
■ In all transformers that are used commercially, the core is made out
of transformer sheet steel laminations assembled to provide a
continuous magnetic path with minimum of air-gap included.
10. ■ The steel should have high permeability and low hysteresis
■ For this to happen, the steel should be made of high silicon
content and must also be heat treated.
■ By effectively laminating the core, the eddy-current losses
can be reduced.
11. ■ The lamination can be done with the help of a light coat of
core plate varnish or lay an oxide layer on the surface.
■ For a frequency of 50 Hertz, the thickness of the
lamination varies from 0.35mm to 0.5mm for a frequency
of 25 Hertz.
12. Types of transformer
■ 2 types
• 1. Core- Type Transformer
• 2. Shell-Type Transformer
■ 1.Core-type Transformer
• the windings are given to a considerable part of the core.
• The coils used for this transformer are form-wound and are
of cylindrical type.
13. • 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
• The low voltage windings are placed nearer to the core
as it is the asiest to insulate.
• The effective core area of the transformer can be
reduced with the use of laminations and insulation.
14. ■ 2. Shell-Type Transformer
• In shell-type transformers, the core surrounds a considerable portion
of the . windings.
• The comparison is shown in the figure below.
• 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.
15. ■ Applications of a transformer
■ Transformers are used in most electronic circuits. A transformer
has only 3 applications;
■ To step up voltage and current.
■ To Step down voltage and current
■ To prevent DC – transformers can pass only Alternating
Currents so they totally prevent DC from passing to the next
17. ■ The most important uses and application of Transformer are:
■ It can rise or lower the level of level of Voltage or Current
( when voltage increases, current decreases and vice virsa
because P =V x I, and Power is same ) in an AC Circuit.
■ It can increase or decrease the value of capacitor, an inductor
or resistance in an AC circuit. It can thus act as an impedance
■ It can be used to prevent DC from passing from one circuit
to the other.
■ it can isolate two circuits electrically.
■ Here we report a facile approach to synthesize a novel nanostructured
thin film comprising Cu nanoparticles (NPs) and reduced graphene
oxide (rGO) on a glassy carbon electrode (GCE) via the direct
electrochemical reduction of a mixture of cupper and graphene oxide
■ The effect of the applied potential on the electrochemical reduction of
CO2 was investigated using linear sweep voltammetric (LSV) and
chronoampero- metric (CA) techniques.
■ Carbon monoxide and formate were found as the main products based
on our GC and HPLC analysis.
19. Results and discussion
■ As seen from the FE-SEM images, a graphene-like thin film was
formed following the electrochemical reduction of graphene oxide
(Fig. 1a), while a crystal-like cluster structure of Cu NPs appeared
subsequent to the electrochemical reduction of the CuSO4
precursor (Fig. 1b).
■ The simultaneous formation of the Cu/rGO thin film was achieved
following the electrochemical reduction of the mixed GO and CuSO4
precursor (Fig. 1c), where Cu NPs with ~20 nm were uniformly
distributed on the rGO sheets.
■ A novel nanostructured Cu/rGO thin film was directly formed on the
GCE surface via a facile one-step electrochemical reduction of their
■ The SEM images showed that Cu nanoparticles were uniformly
distributed on the rGO nanosheets.
■ LSV and CA were em-ployed to study the effect of the applied
potential on the electro-chemical reduction of CO2 and to determine
the instant and the steady- state current efficiency of the Cu/rGO
thin film, demonstrating that the Cu/rGO thin film was highly
efficient for CO2 reduction.