TRANSFORMER
A transformer is a device that
transfers electrical energy between two or more circuits (primary and secondary)
through mutual inductance. In voltage applied one circuit produces magnetic
field into the other circuits.
As the name implies, transformer
transforms voltage from one form to the other i.e from low voltage to high
voltage, and vice versa. In power generating companies, electrical powers are
generated at low voltages and then transform these voltages into a much higher
voltage for transmission but these voltages cannot be consumed by our
appliances. At the distribution level, this is then transformed into low
voltages for our appliances to consumed. The reason for transforming the
voltage to a much higher level is that higher distribution voltages implies
lower currents for the same power and therefore lower I(square)R losses along
the networked grid of cables.
In most electronic devices,
transformers are mostly used to step down 230VAC to lower voltages such as 6,9,12,15,24,60,
and 110volts etc. but in the case of inverter, the transformer is used in step
up operation to step up low voltage from the oscillator into high voltage such
as 230vav.
The two coils of the transformer
are not electrically connected with each other but are instead wrapped together
around a common closed magnetic iron circuit called the “core”. The two coil
windings are electrically isolated from each other but are magnetically linked
through the common core allowing electrical power to be transferred from one
coil to the other. When an electric current passed through the primary winding,
a magnetic field is developed which induces a voltage into the secondary
winding
TRANSFORMER CONSTRUCTION
In the diagram above;
Vp - Primary Voltage
Vs - Secondary
Voltage
Np - Primary Turns
Ns - Secondary Turns
Φ (phi) -
Flux Linkage
When a transformer is used to
“increase” the voltage on its secondary winding with respect to the primary, it
is called a step-up transformer.
When it is used to “decrease” the
voltage on its secondary windings with respect to the primary, it is called a step-down transformer. When a
transformer produces the same voltage on both the primary and secondary
windings, we say its output are identical with respect to the voltage, current,
and power transferred. This type of transformer is called impedance transformer and it is mainly used for impedance matching
network or the isolation of adjoining electrical circuits.
TRANSFORMER TURNS RATIO
Assuming an ideal
transformer and the phase angles: Φp – Φs