TRANSFORMERS
TRANSFORMERS
• is an electrical device that allows
us to maintain power when
increasing or decreasing the
voltage in an alternating current
electrical circuit by means of
electromagnetic induction
• In the case of a perfect
transformer, the power entering
the equipment is equal to the
power received at the output
COMPONENTS
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TYPES OF TRANSFORMERS
Step-up Transformer: A step-up transformer is used to
increase the voltage of an electrical current. It does this
by taking a low voltage input and increasing it to a
higher voltage output. The step-up transformer
accomplishes this by using a larger number of turns in
the secondary coil.
A step-down transformer is used to decrease the
voltage of an electrical current. It does this by using a
larger number of turns in the primary coil.
TYPES OF
TRANSFORMERS
ENERGY LOSSES IN TRANSFORMERS
Transformers, like all devices, are not perfect.
While ideal transformers do not have losses, real
transformers have power losses. A transformer's
output power is always slightly less than the
transformer's input power. These power losses end
up as heat that must be removed from the
transformer. The four main types of loss are resistive
loss, eddy currents, hysteresis, and flux loss.
ENERGY LOSSES IN TRANSFORMERS
Resistive loss, or I2R loss, or copper loss, is the power loss in a
transformer caused by the resistance of the copper wire used to
make the windings. Since higher frequencies cause the electrons to
travel more toward the outer circumference of the conductor (skin
effect), electrical disturbances called harmonics have the effect of
reducing the wire size and increasing resistive loss. These losses are
the same as the power losses in any conductor and are calculated as
follows:
P=I^2R
where
P = power (in W)
I = current (in A)
R = resistance (in Ω)
ENERGY LOSSES IN TRANSFORMERS
ENERGY LOSSES IN TRANSFORMERS
ENERGY LOSSES IN TRANSFORMERS
ENERGY LOSSES IN TRANSFORMERS
Flux loss occurs in a transformer when some
of the flux lines from the primary do not pass
through the core to the secondary, resulting in a
power loss. There are two main reasons for flux lines
to travel through the air instead of through the core.
First, the iron core can become saturated so that the
core cannot accept any more flux lines.
EFFICIENCY OF TRANSFORMERS
• The ratio of a transformer's output power to its input
power is known as transformer efficiency. The effect of
transformer losses is measured by transformer
efficiency, which is typically expressed as a percentage.
The following formula is used to measure transformer
efficiency.
• The efficiencies of power transformers normally vary
from 97 to 99 percent. The power supplied to the load
plus resistive, eddy current, hysteresis, and flux losses
must equal the input power. The input power is always
greater than the output power.
EFFICIENCY OF TRANSFORMERS
MOST
COMMON
CALCULATIONS
MOST
COMMON
CALCULATIONS
SAMPLE
PROBLEMS
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• If a primary coil is rated at 7200 VAC and has 1620 turns, what is
the volts per turn value of the transformer? The transformer
drops 7200 VAC across 1620 turns.
• The number of primary and secondary windings is 90 and 120
respectively. The secondary voltage is given by 310V, which
determines the primary voltage.
• What is the current flowing through the secondary winding if
the primary and secondary windings has 480 turns and 300
turns respectively: assuming that the main source has 12A.
THANK YOU
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