A transformer is a static device that allows the interchange of electrical energy between two ports at different voltage levels. It consists of two insulated windings wrapped around a magnetic core. When an alternating voltage is applied to the primary winding, it produces an alternating magnetic flux that induces a voltage in the secondary winding. The ratio of the number of turns in the windings determines the ratio of the voltages. Transformers can step voltages up or down and are used to change voltage levels in power systems. Transformers are constructed with either core-type or shell-type winding configurations and use thin laminated cores to reduce eddy currents.

1. Introduction to transformers

2. Outline
1. Introduction to Transformers
2. Transformer construction
3. Model of Transformer on no load
Performance
Management
Orientation

3. Transformer
• A transformer is a static device comprising coils coupled through a magnetic
medium connecting two ports at different voltage levels in an electric system
allowing the interchange of electrical energy between the ports
• It is used in changing voltage and current levels in electric power systems
• Other important tasks include matching source and load impedance for
maximum power transfer, and electrical isolation
• A transformer, consists essentially of two insulated windings interlinked by a
mutual magnetic field established in a core of magnetic material

4. Transformer
• When one of the windings, termed the primary, is connected to an
alternating-voltage source, an alternating flux is produced in the core
• This mutual flux links the other winding, called the secondary.
• A voltage is induced in this secondary of the same frequency as the
primary voltage but its magnitude depends on the number of
secondary turns
• The subscript “1”or “p” will be associated with the primary and “2” or “s”
with the secondary

5. Transformer
• If the secondary voltage is greater than the primary value, the
transformer is called a step-up transformer;
• if the secondary voltage is less, it is known as a step-down transformer;
• if primary and secondary voltages are equal, the transformer is said to
have a one-to-one ratio. (these are mostly used for isolation purposes)

6. TRANSFORMER CONSTRUCTION
• Construction of transformers will be dependent on a number of factors
such as:
• Winding voltage
• Current rating and operating frequency
• Heat removal from the core and windings

7. TRANSFORMER CONSTRUCTION
• The primary and secondary coils are wound on the core and are
electrically insulated from each other and from the core
Two types of cores are commonly used—core-type and shell-type
• In core-type construction, the windings are wound around the two legs
of a rectangular magnetic core
• In shell-type construction, the windings are wound on the central leg
of a three-legged core
In either case, the core is constructed of thin laminations electrically
isolated from each other in order to minimize eddy currents

8. TRANSFORMER CONSTRUCTION
• The primary and secondary windings
in a core type transformer are
wrapped one on top of the other
with the low-voltage winding
innermost
• Half of the low-voltage winding and
half of the high-voltage winding is
wound on each limb of the core

9. TRANSFORMER CONSTRUCTION
• Such an arrangement serves two
purposes:
 It simplifies the problem of
insulating the high-voltage winding
from the core.
It results in much less flux leakage
than would be the case if the two
windings were separated by a
distance on the core.

10. TRANSFORMER CONSTRUCTION
• In shell-type construction leakage is reduced by subdividing each
winding into subsections and interleaving LV and HV windings

11. TRANSFORMER CONSTRUCTION
• The shell-type construction has better mechanical support and good
provision for bracing the windings. However, it requires more
specialized fabrication facilities than core-type,
• The core type offers the additional advantage of permitting visual
inspection of coils in the case of a fault and ease of repair.
• In addition, the core type windings can easily be insulated from each
other and from the core
• For this reason, the core type transformers are commonly used in large
high-voltage installations.

12. TRANSFORMER CONSTRUCTION
• Transformer windings are made of solid or stranded copper or
aluminium strip conductors.
• The windings of huge power transformers use conductors with heavier
insulation (cloth and paper.)
• The winding layers are insulated with pressed boards and varnished
cloth