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Power Transformers Encyclopedia

Author: Apogeeweb
Date: 11 Jan 2018
 7050
transformer design calculations

Warm hints: The word in this article is about 3000 and reading time is about 15 minutes.

Introduction

A power transformer is a static machine used for transforming power from one circuit to another without changing frequency. Power transformers are used in the high voltage transmission network to step up and step down the voltage. These transformers are generally used for the purpose of transmission of heavy loads. In more technical terms, when a primary winding is connected to alternating current, it produces alternating magnetic flux. Alternating magnetic flux induces the AC electromotive force in the two winding through magnetic core conduction. This paper will mainly introduces about power transformer, such as the working principle, function of power transformer; the main power transformers or differences between power and distribution transformer.

 

Catalog

Introduction

I What is a Power Transformer?

II Power Transformer Design

III Working Principle of Power Transformer

Ⅳ Power Transformer Parts

  4.1.Original & auxiliary side coil of the ordinary transformer

  4.2. The main power transformers

Ⅴ Why Do We Use Power Transformers?

Ⅵ Distribution Transformer

  6.1 Distribution Transformer Overview

  6.2 Differences Between Power and Distribution Transformer

Ⅶ Frequently Asked Questions about Power Transformer


I What is a Power Transformer?

The power transformer is a static electrical device, which is used to transform a numerical value of alternating voltage (current) into another frequency or the same number of different voltage (current) devices. When a primary winding is connected to alternating current, it produces alternating magnetic flux. Alternating magnetic flux induces the AC electromotive force in the two winding through magnetic core conduction. The height of the two induction electromotive force is related to the number of turns of the one or two winding, that is, the size of the voltage is proportional to the number of turns.

 

The main function is to transmit electric energy, so the rated capacity is its main parameter. Rated capacity is a manifestation of the value of conventional power, it is a characterization of the power transmission size, using kVA or MVA to express, when the rated voltage is applied to the transformer, according to it to determine under specified conditions does not exceed the rated current value of temperature rise.

 

The most energy saving power transformer is the amorphous alloy iron core distribution transformer, its greatest advantage is that the value of the no-load loss is very low. It is the core problem to be considered in the whole process of the whole design. When the product structure is arranged, the amorphous alloy core itself is not affected by external force. Meanwhile, the characteristic parameters of amorphous alloy must be selected accurately and reasonably when calculating.

 

II Power Transformer Design

oil immersed power transformer

Shape Diagram of Three Phase Oil Immersed Power Transformer

In the above picture: The number corresponding to the name is as following:

1 - nameplate

2 - signal thermometer

3 - humidifier

4 - oil mark

5 - oil storage cabinet

6 - safe airway

7 - gas relay

8 - high pressure casing

9 - low voltage casing

10 - tap change

11 - oil tank

12 - oil discharge valve

13 - body

14 - floor

15 - car


Power supply and distribution mode: 10KV high voltage power grid adopts three phase three line neutral point ungrounded system operation mode. The user transformer power supply mostly chooses the neutral point direct grounding system operation mode of Y/Yno junction mode, which can realize three phase four wire system or five wire system power supply, such as TN-S system.

 

III Working Principle of Power Transformer

Do you know how does a power transormer work? Let's see a vedio firstly:

This video gives a detailed animated illustration on the working of electrical Transformers. The basic working principle and

construction of transformer, step-up transformer, step-down transformer, transformer winding and core construction are well illustrated.

The high voltage windings used in domestic transformers are usually connected to Y connection, and the connection between the middle voltage windings and the low voltage windings depends on the system conditions. The system condition refers to the relationship between the voltage phase of the high voltage transmission system and the voltage phase of the medium voltage or low voltage transmission system. If the low voltage system distribution system, it can be determined according to the standard. High voltage winding connection method is often Liancheng Y due to the phase voltage line voltage can be equal to 57.7%, each turn voltage can be lower.

 

(1) The voltage phasors of 500, 330, 220 and 110kV transmission systems are all the same phase in China. 

 

Therefore, the three phase three winding or three phase autotransformer with the following voltage ratio should be connected by star connection. When the iron core structure of three-phase column, low voltage winding can also adopt star connection or angle connection, it depends on the voltage of low voltage power transmission system is phase voltage and high voltage transmission system voltage phasor for the same phase or lag 30 degrees electric angle.

  • 500/220/LVkV - YN, yn0, yn0 or YN, yn0, D11

  • 220/110/LVkV - YN, yn0, yn0 or YN, yn0, D11

  • 330/220/LVkV - YN, yn0, yn0 or YN, yn0, D11

  • 330/110/LVkV - YN, yn0, yn0 or YN, yn0, D11

 

(2) There are two different phase angles in the transmission system voltage of 60 and 35kV.

 

For example, 220/60kV transformer adopts YNd11 connection, and 220/69/10kV transformer is connected with YN, yn0, D11, and the two 60kV transmission systems have a difference of 30 degrees of electrical angle.

 

When 220/110/35kV transformer adopts YN, yn0 and D11 connection, 110/35/10kV transformer adopts YN, yn0 and D11 connection. The voltage phase of the above two 35kV transmission systems is also 30 degrees electric angle.

 

Therefore, it is prudent to determine the connection between the 60 and the 35kV winding, and the connection method must meet the requirements of the voltage phasor of the transmission system. The connection between the 60 and the 35kV stage windings is determined according to the relative relation of the voltage phase quantity. Otherwise, even if the capacity is right, the voltage ratio is also right, the transformer can not be used, the connection is wrong, the transformer can not be connected with the transmission system.

power transformer parts

(3) There are also two phases of the domestic 10, 6, 3 and 0.4kV transmission and distribution systems. 

 

In some Asian areas, there is a 10kV and 110kV transmission system voltage phase difference of 60 degrees electric angle, can use 110/35/10kV at the voltage ratio with YN, yn0, Y10 connection of the three-phase three winding power transformer, but limit the use of three-phase three limb core heart.

 

(4) But note: single-phase transformers connected in three-phase connection method, cannot use the YNy0 connection of the three-phase group. YNy0 connection can not be used in three phase shell transformer.

 

Three-phase five pole transformer must be used in YN, yn0, yn0 connection, in the transformer to be connected into a corner fourth winding connection, it leads to the top (the structure to do electrical test leads out not in this case).

 

(5) When the transformer is in parallel operation in different joint groups, the general regulation is that the connection number must be the same.

 

(6) Distribution transformer is used for lightning intensified area, can use the Yzn11 connection, when using Z method, impedance voltage algorithm and Yyn0 method, and Z method of winding copper consumption to more. The lightning protection performance of Yzn11 distribution transformer is better.

 

(7) The YNy0 connection can not be used when the three-phase transformer uses four coiled core frames.

 

(8) All of the above are used for the connection of domestic transformers. When the export is exported, a suitable connection and joint group label should be supplied as required.

 

(9) In general, the joint and the split switch are connected in the high voltage windings. Therefore, when the selection switch (including load tap changer and no excitation voltage regulating tap switch), must pay attention to the connection with the transformer tap switch connected with (including grounding method, test voltage, rated current, each voltage level, voltage range etc.). The YN connection of the load tap for on load tap changer in transformer, but also pay attention to the midpoint must be able to lead.

 

Ⅳ Power Transformer Parts

4.1. Original & auxiliary side coil of the ordinary transformer

power transformer image

The side coil is concentrically placed on a core column with a low voltage winding and a high voltage winding. The original and secondary coils of the welder transformer are respectively mounted on two iron core columns. When the transformer is running on load, when the secondary side current increases, the transformer must maintain the main flux in the core, and the primary side current must also increase correspondingly to achieve the balance of the secondary side current. The two active power of the transformer is generally equal to the rated capacity of the transformer (KVA) * 0.8 (transformer power factor) = KW.

4.2. The main power transformers

electric transformer

  • Breathers (silica gel tube)

Inside the silicone oil storage cabinet (oil pillow) insulating oil within the breather is communicated with air through the desiccant to absorb moisture in the air and impurities, in order to maintain good insulation performance of transformer winding; silicone discoloration, metamorphic easily lead to clogging.

  • Oil Level Gauge

Reflect the transformer oil level state, in general about +20O, high oil, gas is too low; the winter temperature is low, when the load is light level changes little, or level slightly decreased; the summer temperature rises when the load is heavy, the oil level also increased slightly; two of them are normal.

  • Oil Pillow

Adjust the oil volume of the tank to prevent the overspeed oxidation of the transformer oil, and the upper gas hole.

  • Explosion-proof Pipe

Prevent sudden accident against oil. The increase of pressure in the box causes the danger of explosion.

  • Signal Thermometer

Monitor transformer operating temperature and send out signal. It indicates the oil temperature in the upper layer of the transformer, and the temperature of the transformer coil is 10 degrees centigrade higher than the upper oil temperature. The national standard provides that the limit working temperature of the transformer winding is 105OC, that is, when the ambient temperature is 40OC, the upper layer temperature should not exceed 95OC, usually the monitoring temperature (the upper oil temperature) is set at 85OC or below.

  • Split Switch

By changing the head of the high voltage winding, increasing or reducing the number of winding turns to change the voltage ratio.

where U1/U2=W1/W2,U1W2=U2W1

U2=U1W2/W1

All transformers are no load voltage regulation. They need power outage. They are often divided into +5%, 0% and -5% three, II and III, the first one is 10.5KV, 10KV and 0.95KV are 380V, 400V and 420V two times. G, gas signal relay: (gas relay) light gas, heavy gas signal protection. On the contact point for the light gas signal is generally applied to signal to the alarm, said transformer abnormal operation; under the contact point for the heavy gas signal, at the same time after the action signal to trip the circuit breaker and drop alarm; general gas relay filled with oil description without gas tank, gas will enter the gas relay within reach to some extent, crowding out the gas oil contact action; open the gas relay cover, the top two adjusting rod, unscrew one cap can be released within the gas relay; the other is the adjusting rod protection test button; charged operating gloves and safety must be emphasized.

transformer

Ⅴ Why Do We Use Power Transformers?

Power transformers are one of the main equipment for power plants and substations. The functions of transformers are manifold. They can not only increase the voltage, but also reduce the voltage to voltage at all levels, so as to meet the need of electricity. In a word, both the boost and the depressurization must be done by the transformer. In the process of power transmission, there will be two parts of voltage and power loss. When transporting the same power, the voltage loss is inversely proportional to the voltage, and the power loss is inversely proportional to the square of the voltage. The voltage is raised by using the transformer, and the loss of power supply is reduced.

 

The transformer is composed of two or more than two winding coils that are wound around the same core. The winding is connected by alternating magnetic field, and works according to the electromagnetic induction principle. The installation position of the transformer should be considered for easy operation, maintenance and transportation, and the safe and reliable place should be selected. The rated capacity of the transformer must be reasonably selected when the transformer is used.

 

When the transformer is running in no-load, it needs greater reactive power. The reactive power is supplied by the power supply system. If the capacity of the transformer is too large, it will not only increase the initial investment, but also make the transformer run at no load or light load for a long time. It will increase the proportion of no load loss, reduce the power factor and increase the network loss. So the operation is neither economical nor unreasonable. The transformer capacity is too small, which will make the transformer overload for a long time and easily damage the equipment. Therefore, the rated capacity of the transformer should be selected according to the needs of the electric load, so it should not be too large or too small. More detailed please look at Part Five.

 

Ⅵ Distribution Transformer

6.1 Distribution Transformer Overview

When it comes to power transformer, people think of a distribution transformer. Let’s also understand something about distribution transformer.

 

The distribution power transformer is a static electrical equipment, which is used to transform a numerical value of alternating voltage (flow) into another frequency or the same number of different voltage (current) devices. When a primary winding is connected to alternating current, it produces alternating magnetic flux. Alternating magnetic flux induces the AC electromotive force in the two winding through magnetic core conduction. The height of the two induction electromotive force is related to the number of turns of the one or two winding, that is, the size of the voltage is proportional to the number of turns.

 

The main function is to transmit electric energy, so the rated capacity is its main parameter. Rated capacity is a manifestation of the value of conventional power, it is a characterization of the power transmission size, with kVA or MVA, when the rated voltage is applied to the transformer, according to it to determine under specified conditions does not exceed the rated current value of temperature rise. The most energy saving power transformer is the amorphous alloy iron core distribution transformer, its greatest advantage is that the value of the no-load loss is very low. It is the core problem to be considered in the whole process of the whole design. When the product structure is arranged, the amorphous alloy core itself is not affected by external force. Meanwhile, the characteristic parameters of amorphous alloy must be selected accurately and reasonably when calculating.

electrical transformer

6.2 Differences Between Power and Distribution Transformer

All the transformers used in the power network are called power transformers, which are all levels of transformer used before distribution, and the general low voltage is 3kV and above. The transformer that reduces the voltage to the working voltage of the electrical equipment is called the distribution transformer, which is used for daily lighting and factory power, and the general low voltage is 0.4kV or less.

 

The distribution power transformer is a static electrical equipment, which is used to transform a numerical value of alternating voltage (current) into another frequency or the same number of different voltage (current) devices. When a primary winding is connected to alternating current, it produces alternating magnetic flux. Alternating magnetic flux induces the AC electromotive force in the two winding through magnetic core conduction. The height of the two induction electromotive force is related to the number of turns of the one or two winding, that is, the size of the voltage is proportional to the number of turns.

 

The main function is to transmit electric energy, so the rated capacity is its main parameter. Rated capacity is a manifestation of the value of conventional power, it is a characterization of the power transmission size, with kVA or MVA, when the rated voltage is applied to the transformer, according to it to determine under specified conditions does not exceed the rated current value of temperature rise. Now the more energy saving power transformer is the amorphous alloy iron core distribution transformer, its biggest advantage is that the value of the no-load loss is very low. It is the core problem to be considered in the whole process of the whole design. When the product structure is arranged, the amorphous alloy core itself is not affected by external force. Meanwhile, the characteristic parameters of amorphous alloy must be selected accurately and reasonably when calculating.

 

Relevant information about "Power Transformers Encyclopedia"

About the article "Power Transformers Encyclopedia", If you have better ideas, don't hesitate to  write your thoughts in the following comment area. You also can find more articles about electronic semiconductor through Google search engine, or refer to the following related articles.

 

Ⅶ Frequently Asked Questions about Power Transformer

1. What is power transformer?
One of the important and commonly used Transformer is Power transformer. It is very widely used for stepping up and stepping down the voltage at the electrical power generating station and distribution station (or substation) respectively. Power transformer is used two times while delivering electric power to a consumer who is far away from the generating station.

 

2. How does a power transformer work?
A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. It can be designed to "step up" or "step down" voltages and works on the magnetic induction principle. ... A voltage is then induced in the other coil, called the secondary or output coil. Power transformer is used two times while delivering electric power to a consumer who is far away from the generating station.

 

3. What is the purpose of a power transformer?

A transformer is an electrical device that trades voltage for current in a circuit, while not affecting the total electrical power. This means it takes high-voltage electricity with a small current and changes it into low-voltage electricity with a large current, or vice versa.

 

4. What is the difference between a power transformer and a distribution transformer?
Main Differences. Power transformers are used in transmission network of higher voltages for step-up and step down application (400 kV, 200 kV, 110 kV, 66 kV, 33kV) and are generally rated above 200MVA. Distribution transformers are used for lower voltage distribution networks as a means to end user connectivity.

 

5. What is in a power transformer?
Three Phase Transformer
The skeleton has three columns on which windings of three phases are wound. The lower voltage winding is wound first and is wound closer to the core while higher voltage winding is wound on top of the lower-voltage winding. Do remember, both the windings are separated by an insulation layer.

 

6. What is the efficiency of power transformer?
Efficiency of Transformer
Transformers are the most highly efficient electrical devices. Most of the transformers have full load efficiency between 95% to 98.5%.

 

7. How much is a power transformer?
As for power transformer price
Power pole transformers cost anywhere from $3,000 to $7,000 each, depending on how much electricity they're designed to handle. The money comes from utility customers.

 

8. Where are power transformers used?
Power transformers are used in transmission network of higher voltages for step-up and step down application (400 kV, 200 kV, 110 kV, 66 kV, 33kV) and are generally rated above 200MVA. Distribution transformers are used for lower voltage distribution networks as a means to end user connectivity.

 

9. Why do we use power transformers?
Power transformers are used in the high voltage transmission network to step up and step down the voltage. These transformers are generally used for the purpose of transmission of heavy loads. ... Naturally, power transformers have the corresponding copper losses and iron losses at higher load.

 

10. How do I know if my power transformer is bad?
A bad transformer will have weak power or none at all. If there is power to the unit, it may not be faulty. However, if there is little or no power going to the unit, it may need replacement or repairs. A simple way to check the power is to turn the unit off and on again.

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pinglun 2 comments

    • pingluntus
    • Kent on 2018/8/24 3:42:58

    It works really well for me

    • pingluntus
    • Www.Googleplusghosts.Com on 2018/8/29 19:02:41

    It works quite well for me

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