6 Types of Losses in a Transformer

Since a perfect  transformer is extremely efficient and doesn’t lose power, the power applied to its input side should be equal to the power applied to its output side. As a result, a perfect transformer has no friction, no static losses, and equal input and output power. However, in reality, the transformer’s electrical input and output power won’t be equal because of internal electrical losses. Because it is an electrical static device without any moving parts, we cannot see mechanical losses, but there will be electrical losses like those from copper and iron. This article describes the different types of significant losses that can happen in transformers.

Types of Losses in a Transformer

1-Iron loss, 2—copper loss, 3—hysteresis loss, 4—eddy loss, 5—stray loss, and 6—dielectric loss, among other types of power and distribution transformer losses, will all occur in the transformer. While copper loss is primarily brought on by resistance in the transformer’s two windings, hysteresis losses are based on a change in magnetization within the transformer core.

Loss of iron in a power and distribution transformer

The alternating flux inside the transformer’s core is the primary cause of iron losses. Core loss refers to this loss when it occurs inside the core. The core loss is mostly caused by the electromagnetic properties of the material in the power and distribution transformer cores. These losses are known as “iron losses” because iron may be used to produce the transformer’s core. Hysteresis and eddy current losses are comparable to this loss.

The magnetic field of a transformer is altered when alternating current (AC) is applied to its core, which frequently results in this loss. The transformer’s core material has a major impact on this loss. The usage of the top quality core material might minimize this loss. In order to decrease hysteresis loss, CRGO- Cold rolled grain-oriented Silicon steel sheet—is regularly utilized as a transformer core. This core loss can be described using the below following equation :

Ph = Khxf Bxm

The transformer’s “kh” constant is based on  the quality and quantity of the T/F core material.

The core’s maximum flux density is designated as “Bm.”

“F” is the alternating change able flux 

The Steinmetz constant is “x,” and its value typically falls between 1.5 and 2.5 tesla.

The Eddy Current (Io) Losses in a power and distribution  transformer core

Ferromagnetic material is a good conductor as well, and a core constructed of one of these materials has a single short-circuited turn along the length of it. As a result, eddy currents go through the transformer core in a plane normal to the magnetic flux, which causes the core material to heat up resistively.

The eddy current loss is a complicated function of the inverse square ^2 of the material thickness and the square ^2 of the supply frequency. When compared to a solid block, a stack of plates with an electrically isolated core will have less eddy current losses than a solid block. All transformers that operate at low frequencies have laminated or related cores.

Pe = KeBm2t2f2V watts

Where,

“Ke” is used for  eddy current coefficients. This number mostly depends on the properties of the magnetic materials, such as resistivity, core material volume, and lamination width.

“Bm” is the rate of the flux Φ  density in wb/m2

“T” is the  Width of core lamination in meters

“F” is the magnetic field’s reversal frequency, represented in Hz.

The amount of core magnetic materials in m3 is represented by the symbol “V.”

 Loss of copper in a transformer winding

I2R loss in the transformer’s both windings causes the copper loss, which results in energy loss as heat. The current rises as the transformer load increases because the primary input and secondary output currents are proportional to the % percentage of loading. As both the primary input and secondary output currents rise, the full load on the transformer makes the copper loss go up.

As the full load  on the  transformer is raised, the copper loss value changes and is not constant. The both windings copper losses are sometimes referred to as “changeable losses” because of this.

the services and increase the transformer’s total winding copper loss (I2R) loss. The square ^2 of the RMS current flowing through the winding and the resistance (Ohm) of the winding are both related to the copper losses. As the temperature rises, the conductor’s resistance changes.

The copper losses in the transformer are based on the relationship between the rated current flowing through the winding and its square. Because of the increased output current and higher resistance brought on by a change in temperature, the both winding copper loss fluctuates when the output load on the transformer is raised.

The resistance in ohms of the copper material or aluminum material must be changed in order to increase the transformer winding as much as is permitted while maintaining the transformer’s rated capacity. For an oil cooled power and distribution  transformer, the HV and LV resistance of the both winding is measured at 25° C or  must be changed for 75° C.

The following formula can be used to evaluate the increase in resistance with temperature.

Temperature MF = (235+75° C)/(235+Ambient temperature Or 25° C)

A stray loss in the active part of a  power and distribution transformer

Stray losses are caused by a flux leak in the  transformer. This leakage flux causes eddy currents, also known as stray losses, to occur everywhere in metal components that are exposed to the magnetic leakage field.

The leakage flux can be minimized to prevent stray losses.

Dielectric Losses in transformer Oil and active part

It occurs in the transformer’s insulating materials, which is dissolved in its oil. It happens when the oil and insulating materials start to degrade. The properties of transformer oils can alter, including their dielectric strength, tan, moisture content, chemical parameters (dissolved contaminants – copper dissolution), physical parameters, etc.

Dielectric loss may be effectively reduced by routine oil testing and maintaining high-quality insulation.

Auxiliary losses in Transformer

These losses are based on by the energy required to power pumps or fans that help cool larger transformers.

Extra losses resulting from harmonics and unbalance

Extra losses come from distorted or imbalanced voltages or currents.
Eddy current power losses are directly related to the square of the frequency of the supply. Since harmonic frequencies are higher than the rated frequency, this means that the core and windings lose more power.
Negative sequence voltages are transformed by transformers the same way positive sequence voltages are transformed. The behavior in relation to homopolar voltages is influenced by the primary and secondary connections, and more specifically by the presence of a neutral conductor.