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A
single phase transformer is made up of two coils of wire, also known as
windings. These are wound on a type of core material. Typically these windings
are wound in either a rectangular or cylindrical form around a separate
core/limb which is made up from soft iron. The primary winding is the one that
connects directly to the source, the secondary is the one that connects
directly to the load. The diagram below displays what the primary and secondary
windings look like.

Although
it looks like it the two coils are not in electrical contact with one another,
in fact they are wrapped closely together around a common closed magnetic iron
circuit which is referred to as the ‘core’. The soft iron core is not actually
a complete solid, it consists of individual laminations that are combined to
avoid losses within the core. The primary and secondary windings are
magnetically linked through the common core but are completely electrically
isolated from one another. This enables electrical power to be conveyed from
one coil to another. A magnetic field can be formed when an electrical current
flows through the primary winding, this then induced a voltage through the
secondary winding.

 

A
three phase transformer can be made up in two different ways, core or shell.

The
core type consists of three individual limbs made up of individual laminations.
Each singular limb has cylindrical shaped primary and secondary windings which
are aligned concentrically. The diagram below shows what the core type
construction looks like.

 

The
alternative construction is the shell type, this type is similar to the core
construction, the difference is that within this arrangement each phase has its
own personal magnetic circuit. Also the windings are wound around the limbs
horizontally instead of vertically. The diagram below illustrates what a shell
type transformer looks like.

Single
phase transformers tend to be generally small in size and can be found on most
roads/streets. They are usually in metal shed surrounded by a fence/guard, this
is to avoid any trespassers gaining entrance and potentially causing damage or
hurting themselves. The transformer should be able to work well in warm, cold
and wet weathers. Although the transformer is in a shed it is not completely
resistant to these environments therefore it should be able to withstand them
and function properly.

 

Three
phase transformers are to be treated differently as they are potentially far
more dangerous. These transformers are sometimes stored in a safe place that is
not so easy to access. Being stored in a secured area also allows for a forced
air flow to assist the transformer in keeping cool.

A transformer under ‘no load’ conditions has no
load on the secondary side of the transformer, this means that the secondary
winding is open circuited. The current

within the secondary will remain at zero, on the
other hand the primary windings will hold a small amount of current which is
referred to as a ‘no load current’ this is typically around two to ten percent
of the rated current. This current has the responsibility of supplying iron
losses inside of the core. It is also responsible for a very small amount of
copper loss from the primary winding.

A transformer under a loaded condition has a load
connected to the secondary winding, which makes the transformer loading greater
than zero. A current travels from the secondary winding then out through the
load. The load can be one of three things; resistive, capacitive or inductive. The
secondary current is caused by the induced secondary voltage, this is set up by
the magnetic flux that is created in the core of the primary current. The
secondary current creates a self-induced secondary magnetic field which is
located inside the core of the transformer. The two magnetic fields repel each
other which creates a combined magnetic field of less magnetic strength than a
singular field produced by the primary winding alone, when the secondary
circuit was open circuited. The combination of the magnetic fields reduces the
back EMF of the primary winding, this resulting in a slight increase of the
primary current. This current will continue to increase until the cores
magnetic field returns to its original strength. To ensure to transformer
operates correctly here must be a balanced condition existing between the
primary and secondary magnetic fields. This will result in the power being
balanced and the same on both primary and secondary sides.

In
primary winding, each phase is 120 degrees out of phase with the other two
phases, this is also the same in secondary winding. The individual primary
windings are linked magnetically to a singular secondary winding through a
common core leg. In the vector diagram, sets of windings that are linked
magnetically are drawn parallel to each other. Within this type of connection
both the primary and secondary windings are connected to a neutral point. This neutral
point can be brought out to an external physical connection and can also be
grounded.

Advantages
of Star-star:

·        
Suitable for three phases four wire systems

·        
Can handle heavy loads

·        
Elimination of distortion in the secondary phase voltage

·        
Better protective relaying

Disadvantages
of Star-star

·        
There can be a large voltage drop for unbalanced phase to neutral loads

·        
Transformer tank overheating

·        
Over voltage at light load

Within
the Delta-star connection, the primary is connected in a delta arrangement and secondary
is connected to star. The main application of this connection is to step up the
voltage. For example, this could be at the beginning of a high tension
transmission system. Between both the primary and secondary line voltage you
can find a phase shift of 30 degrees.

Below
is images of the Delta-Star connection and the Phase shift of 30 degrees
between both primary and secondary line voltage.

Due
to the primary being delta connected, the line voltage on the primary side is equal
to the phase voltage on the secondary side. Now transformation ration, also
known as (K) is equal to the secondary phase voltage divided by the primary
phase voltage. The secondary phase voltage is equal to (K) times primary phase
voltage.

Due
to the secondary being star connected the line voltage on the secondary side is
equal to  times the phase voltage on the secondary side.

Line voltage
on the secondary side =  x (K) x primary phase voltage.

Line voltage
on tA
single phase transformer is made up of two coils of wire, also known as
windings. These are wound on a type of core material. Typically these windings
are wound in either a rectangular or cylindrical form around a separate
core/limb which is made up from soft iron. The primary winding is the one that
connects directly to the source, the secondary is the one that connects
directly to the load. The diagram below displays what the primary and secondary
windings look like.

Although
it looks like it the two coils are not in electrical contact with one another,
in fact they are wrapped closely together around a common closed magnetic iron
circuit which is referred to as the ‘core’. The soft iron core is not actually
a complete solid, it consists of individual laminations that are combined to
avoid losses within the core. The primary and secondary windings are
magnetically linked through the common core but are completely electrically
isolated from one another. This enables electrical power to be conveyed from
one coil to another. A magnetic field can be formed when an electrical current
flows through the primary winding, this then induced a voltage through the
secondary winding.

 

A
three phase transformer can be made up in two different ways, core or shell.

The
core type consists of three individual limbs made up of individual laminations.
Each singular limb has cylindrical shaped primary and secondary windings which
are aligned concentrically. The diagram below shows what the core type
construction looks like.

 

The
alternative construction is the shell type, this type is similar to the core
construction, the difference is that within this arrangement each phase has its
own personal magnetic circuit. Also the windings are wound around the limbs
horizontally instead of vertically. The diagram below illustrates what a shell
type transformer looks like.

Single
phase transformers tend to be generally small in size and can be found on most
roads/streets. They are usually in metal shed surrounded by a fence/guard, this
is to avoid any trespassers gaining entrance and potentially causing damage or
hurting themselves. The transformer should be able to work well in warm, cold
and wet weathers. Although the transformer is in a shed it is not completely
resistant to these environments therefore it should be able to withstand them
and function properly.

 

Three
phase transformers are to be treated differently as they are potentially far
more dangerous. These transformers are sometimes stored in a safe place that is
not so easy to access. Being stored in a secured area also allows for a forced
air flow to assist the transformer in keeping cool.

A transformer under ‘no load’ conditions has no
load on the secondary side of the transformer, this means that the secondary
winding is open circuited. The current

within the secondary will remain at zero, on the
other hand the primary windings will hold a small amount of current which is
referred to as a ‘no load current’ this is typically around two to ten percent
of the rated current. This current has the responsibility of supplying iron
losses inside of the core. It is also responsible for a very small amount of
copper loss from the primary winding.

A transformer under a loaded condition has a load
connected to the secondary winding, which makes the transformer loading greater
than zero. A current travels from the secondary winding then out through the
load. The load can be one of three things; resistive, capacitive or inductive. The
secondary current is caused by the induced secondary voltage, this is set up by
the magnetic flux that is created in the core of the primary current. The
secondary current creates a self-induced secondary magnetic field which is
located inside the core of the transformer. The two magnetic fields repel each
other which creates a combined magnetic field of less magnetic strength than a
singular field produced by the primary winding alone, when the secondary
circuit was open circuited. The combination of the magnetic fields reduces the
back EMF of the primary winding, this resulting in a slight increase of the
primary current. This current will continue to increase until the cores
magnetic field returns to its original strength. To ensure to transformer
operates correctly here must be a balanced condition existing between the
primary and secondary magnetic fields. This will result in the power being
balanced and the same on both primary and secondary sides.

In
primary winding, each phase is 120 degrees out of phase with the other two
phases, this is also the same in secondary winding. The individual primary
windings are linked magnetically to a singular secondary winding through a
common core leg. In the vector diagram, sets of windings that are linked
magnetically are drawn parallel to each other. Within this type of connection
both the primary and secondary windings are connected to a neutral point. This neutral
point can be brought out to an external physical connection and can also be
grounded.

Advantages
of Star-star:

·        
Suitable for three phases four wire systems

·        
Can handle heavy loads

·        
Elimination of distortion in the secondary phase voltage

·        
Better protective relaying

Disadvantages
of Star-star

·        
There can be a large voltage drop for unbalanced phase to neutral loads

·        
Transformer tank overheating

·        
Over voltage at light load

Within
the Delta-star connection, the primary is connected in a delta arrangement and secondary
is connected to star. The main application of this connection is to step up the
voltage. For example, this could be at the beginning of a high tension
transmission system. Between both the primary and secondary line voltage you
can find a phase shift of 30 degrees.

Below
is images of the Delta-Star connection and the Phase shift of 30 degrees
between both primary and secondary line voltage.

Due
to the primary being delta connected, the line voltage on the primary side is equal
to the phase voltage on the secondary side. Now transformation ration, also
known as (K) is equal to the secondary phase voltage divided by the primary
phase voltage. The secondary phase voltage is equal to (K) times primary phase
voltage.

Due
to the secondary being star connected the line voltage on the secondary side is
equal to  times the phase voltage on the secondary side.

Line voltage
on the secondary side =  x (K) x primary phase voltage.

Line voltage
on the secondary side =  x (K) x primary line voltage.

 

The advantages
of Delta-Star connection:

 

·        
Cross section area in winding is less at primary
side

·        
Used at three phase four wire systems

·        
Can handle large unbalanced loads

·        
No distortion of secondary voltage

 

The
disadvantages of Delta-Star connection:

 

·        
Cannot operate in parallel as the secondary voltage
is not in phase with the primary

·        
Secondary voltage is shifted by 30 degrees with
respect to primary voltage. This becomes a problem when paralleling three phase
transformers.

 

As previously
stated, this type of connection is typically used in a step up transformer. It is
commonly used within the commercial and industrial sector, also high-density
residential locations. This is to supply three phase distribution systems.he secondary side =  x (K) x primary line voltage.

 

The advantages
of Delta-Star connection:

 

·        
Cross section area in winding is less at primary
side

·        
Used at three phase four wire systems

·        
Can handle large unbalanced loads

·        
No distortion of secondary voltage

 

The
disadvantages of Delta-Star connection:

 

·        
Cannot operate in parallel as the secondary voltage
is not in phase with the primary

·        
Secondary voltage is shifted by 30 degrees with
respect to primary voltage. This becomes a problem when paralleling three phase
transformers.

 

As previously
stated, this type of connection is typically used in a step up transformer. It is
commonly used within the commercial and industrial sector, also high-density
residential locations. This is to supply three phase distribution systems.

Post Author: admin