Power Transformer Buying Guide
It is universally acknowledged that power transformer stands as INGBO VILLE ENTERPRISE CO.,LTD.'s main and featured product. We have gained wide recognition and high appraises from all over the world for the product with our pro-environment adherence and strong dedication to sustainable development. Research and development and comprehensive market research have been thoroughly conducted before it is launched so that it highly meets the market demand.
The Ville Transformer branded products in our company are warmly welcome. Statistics show that nearly 70% of the visitors to our website will click specific product pages under the brand. The quantity of order and sales volume are both evidence. In China and foreign countries, they enjoy high reputation. Many producers may set them as examples during manufacturing. They are strongly recommended by our distributors in their districts.
We can match your current design specification or custom-design new packaging for you. Either way, our world-class design team will review your needs and suggest realistic options, taking into consideration your time frame and budget. Over the years we have invested heavily in state-of-the-art technology and equipment, enabling us to produce samples of products at with ultimate quality and precision in-house.
no data
1
Causes and Preventive Measures of Power Transformer Burning
(1) Lightning strike. Most of the high-voltage and low-voltage lines of power transformers are introduced by overhead lines. Because they are located in mountainous forest land, the probability of lightning stroke is high. Therefore, in the annual thunderstorm season, the proportion of distribution transformers damaged by lightning stroke accounts for more than 30% of the overhaul.
(2) Ferromagnetic resonance occurs in the system. The rural 10kV distribution line has the condition of overvoltage. When the system resonance overvoltage occurs, the primary current of the transformer will surge. At this time, in addition to fusing the fuse at the primary side of the transformer, it will also damage the transformer winding. In some cases, it will also cause flashover or explosion of transformer bushing.
(1) The short-circuit fault of low-voltage line and the sharp increase of load make the current of transformer exceed dozens of times of rated current. At this time, the winding is displaced and deformed due to the influence of great electromagnetic torque. Due to the sharp increase of current, the temperature rises rapidly, resulting in accelerated aging of insulation.
(2) The winding insulation is damp. This is caused by poor insulation oil quality or low oil level. First, during the storage, transportation or operation and maintenance of transformer insulating oil, water, impurities or other oil stains are inadvertently mixed into the oil, which greatly reduces the insulation strength. Second, during manufacturing, the inner layer of the winding is not fully impregnated and dried, the winding lead joint is poorly welded, and the insulation is incomplete, resulting in inter turn and inter layer short circuit. Third, the decrease of oil level will increase the contact surface between insulating oil and air, accelerate the water in the air into the oil, and also reduce its insulation strength. When the insulation is reduced to a certain value, a short circuit will occur.
(1) Oil leakage of transformer makes the tap changer exposed in the air, and the performance decreases after the insulation is damp, resulting in discharge short circuit and damage to the transformer.
(2) The oil temperature is too high. The oil in the transformer mainly plays the role of insulation, heat dissipation and moisture-proof for the winding. If the oil temperature in the transformer is too high, it will directly affect the normal operation and service life of the transformer.
(3) The tap changer has poor quality, unreasonable structure, insufficient pressure and unreliable contact. The position of the external word wheel is not completely consistent with the internal actual position, resulting in incomplete contact of the star moving contact. The misplaced moving and static contacts reduce the insulation distance between the two taps, and short circuit or ground discharge occurs under the action of the potential between the two taps, The short-circuit current will soon burn out the tap turns and even damage the whole winding.
Oil leakage is the most common appearance abnormality of the transformer. Because the transformer body is full of oil, rubber beads and rubber pads are clamped at each connecting part to prevent leakage. After long-term operation of the transformer, the rubber beads and rubber pads will age and crack, resulting in oil leakage. Of course, if the screw is loose or the oil drain valve is not closed tightly, there will be sand holes or poor welding quality during manufacturing.
(1) The multi-point grounding of 10kV distribution transformer iron core is not easy to find and test, because the iron core grounding of distribution transformer is internally clamped with a very thin red copper sheet, one end is clamped between the iron core (silicon steel sheet), and the other end is pressed on the iron core clamp plate and directly connected with the transformer shell.
(2) Short circuit between iron core and silicon steel sheet. Although the silicon steel sheets are coated with insulating paint, the insulation resistance is very small, which can only isolate the eddy current and can not prevent the high-voltage induced current. If the insulating paint on the surface of silicon steel sheet is naturally aged, it will produce great eddy current loss and increase the local overheating of the iron core.
(1) The uneven three-phase load distribution of distribution transformer leads to the asymmetry of three-phase current. The asymmetric current makes the transformer impedance step-down asymmetric, so the low-voltage three-phase voltage is unbalanced, which is unfavorable to the transformer and users' electrical equipment.
(2) When grounding and phase-to-phase short circuit occur at the low-voltage side of the transformer, a short-circuit current 20 30 times higher than the rated current will be generated. Such a large current acts on the high-voltage winding, and a large mechanical stress will be generated inside the coil. This mechanical stress will cause the coil to compress, and the stress will disappear after the short-circuit fault is removed. If the coil is repeatedly subjected to the mechanical stress, The insulating pad and backing plate will loosen and fall off; The iron core clamping plate screws will also be loose, and the high-voltage coil will be distorted or cracked. In addition, the temperature will be several times higher than the allowable temperature rise, resulting in the burning of the transformer in a very short time.
(1) The outgoing line of the transformer is a copper screw, while the overhead line generally adopts aluminum core rubber wire, so it is easy to produce electrochemical corrosion between copper and aluminum. Under the action of ionization, an oxide film is formed between copper and aluminum, increasing the contact resistance, burning or melting the screw, nut and lead at the lead.
(2) Bushing flashover discharge is also one of the common appearance abnormalities of transformer. Metal dust with conductive properties in the air is attached to the surface of the bushing. In case of rain, snow and humid weather, resonance of the power grid system and lightning overvoltage, the bushing flashover discharge or explosion will occur.
(3) In the process of fastening or loosening the lead nut of the transformer, the conductive screw rotates, resulting in the torsion of the lead of the high-voltage coil inside the transformer or the collision of the soft copper strip led out by the low-voltage, resulting in phase to phase short circuit.
(4) When overhauling the hanging core, it is not carried out according to the maintenance procedures and process standards. It is often careless to damage the insulation of coils, leads, tap changers, etc., or leave tools in the transformer. In some cases, flickering occurs, or short-circuit grounding occurs.
(1) Regularly check whether the three-phase current is balanced or exceeds the rated value. If the three-phase load current is seriously unbalanced, take measures to adjust it in time; Check whether the oil level of the transformer is normal and whether there is leakage. If any, replenish the oil as soon as possible to avoid the tap changer and coil exposed to moisture in the air.
(2) Regularly clean the dirt on the surface of distribution transformer bushing: check whether the bushing has flashover marks, whether the grounding is good, and whether the grounding lead has broken strands, desoldering and fracture; The grounding resistance detected with a megger shall not be greater than 4 .
(3) Reasonably select the wiring mode of low-voltage side conductor, such as copper aluminum transition clamp or terminal block. Apply conductive paste on the contact surface to increase the contact area and prevent heating and oxidation.
(4) According to the technical requirements of 10 / 0.4kV distribution transformer, a set of lightning arresters shall be installed at the high and low voltage sides close to the transformer.
(5) When switching the tap changer, the DC resistance values of the first and second times must be measured with an electric bridge, and records must be made to compare whether the three-phase DC resistance is balanced (the phase to phase difference is no more than 4%, and the line to line difference is no more than 2%). Compare the DC resistance value after switching with the previous records before switching, and put into operation after confirming that the switching is normal.
![]()
(2) Ferromagnetic resonance occurs in the system. The rural 10kV distribution line has the condition of overvoltage. When the system resonance overvoltage occurs, the primary current of the transformer will surge. At this time, in addition to fusing the fuse at the primary side of the transformer, it will also damage the transformer winding. In some cases, it will also cause flashover or explosion of transformer bushing.
(1) The short-circuit fault of low-voltage line and the sharp increase of load make the current of transformer exceed dozens of times of rated current. At this time, the winding is displaced and deformed due to the influence of great electromagnetic torque. Due to the sharp increase of current, the temperature rises rapidly, resulting in accelerated aging of insulation.
(2) The winding insulation is damp. This is caused by poor insulation oil quality or low oil level. First, during the storage, transportation or operation and maintenance of transformer insulating oil, water, impurities or other oil stains are inadvertently mixed into the oil, which greatly reduces the insulation strength. Second, during manufacturing, the inner layer of the winding is not fully impregnated and dried, the winding lead joint is poorly welded, and the insulation is incomplete, resulting in inter turn and inter layer short circuit. Third, the decrease of oil level will increase the contact surface between insulating oil and air, accelerate the water in the air into the oil, and also reduce its insulation strength. When the insulation is reduced to a certain value, a short circuit will occur.
(1) Oil leakage of transformer makes the tap changer exposed in the air, and the performance decreases after the insulation is damp, resulting in discharge short circuit and damage to the transformer.
(2) The oil temperature is too high. The oil in the transformer mainly plays the role of insulation, heat dissipation and moisture-proof for the winding. If the oil temperature in the transformer is too high, it will directly affect the normal operation and service life of the transformer.
(3) The tap changer has poor quality, unreasonable structure, insufficient pressure and unreliable contact. The position of the external word wheel is not completely consistent with the internal actual position, resulting in incomplete contact of the star moving contact. The misplaced moving and static contacts reduce the insulation distance between the two taps, and short circuit or ground discharge occurs under the action of the potential between the two taps, The short-circuit current will soon burn out the tap turns and even damage the whole winding.
Oil leakage is the most common appearance abnormality of the transformer. Because the transformer body is full of oil, rubber beads and rubber pads are clamped at each connecting part to prevent leakage. After long-term operation of the transformer, the rubber beads and rubber pads will age and crack, resulting in oil leakage. Of course, if the screw is loose or the oil drain valve is not closed tightly, there will be sand holes or poor welding quality during manufacturing.
(1) The multi-point grounding of 10kV distribution transformer iron core is not easy to find and test, because the iron core grounding of distribution transformer is internally clamped with a very thin red copper sheet, one end is clamped between the iron core (silicon steel sheet), and the other end is pressed on the iron core clamp plate and directly connected with the transformer shell.
(2) Short circuit between iron core and silicon steel sheet. Although the silicon steel sheets are coated with insulating paint, the insulation resistance is very small, which can only isolate the eddy current and can not prevent the high-voltage induced current. If the insulating paint on the surface of silicon steel sheet is naturally aged, it will produce great eddy current loss and increase the local overheating of the iron core.
(1) The uneven three-phase load distribution of distribution transformer leads to the asymmetry of three-phase current. The asymmetric current makes the transformer impedance step-down asymmetric, so the low-voltage three-phase voltage is unbalanced, which is unfavorable to the transformer and users' electrical equipment.
(2) When grounding and phase-to-phase short circuit occur at the low-voltage side of the transformer, a short-circuit current 20 30 times higher than the rated current will be generated. Such a large current acts on the high-voltage winding, and a large mechanical stress will be generated inside the coil. This mechanical stress will cause the coil to compress, and the stress will disappear after the short-circuit fault is removed. If the coil is repeatedly subjected to the mechanical stress, The insulating pad and backing plate will loosen and fall off; The iron core clamping plate screws will also be loose, and the high-voltage coil will be distorted or cracked. In addition, the temperature will be several times higher than the allowable temperature rise, resulting in the burning of the transformer in a very short time.
(1) The outgoing line of the transformer is a copper screw, while the overhead line generally adopts aluminum core rubber wire, so it is easy to produce electrochemical corrosion between copper and aluminum. Under the action of ionization, an oxide film is formed between copper and aluminum, increasing the contact resistance, burning or melting the screw, nut and lead at the lead.
(2) Bushing flashover discharge is also one of the common appearance abnormalities of transformer. Metal dust with conductive properties in the air is attached to the surface of the bushing. In case of rain, snow and humid weather, resonance of the power grid system and lightning overvoltage, the bushing flashover discharge or explosion will occur.
(3) In the process of fastening or loosening the lead nut of the transformer, the conductive screw rotates, resulting in the torsion of the lead of the high-voltage coil inside the transformer or the collision of the soft copper strip led out by the low-voltage, resulting in phase to phase short circuit.
(4) When overhauling the hanging core, it is not carried out according to the maintenance procedures and process standards. It is often careless to damage the insulation of coils, leads, tap changers, etc., or leave tools in the transformer. In some cases, flickering occurs, or short-circuit grounding occurs.
(1) Regularly check whether the three-phase current is balanced or exceeds the rated value. If the three-phase load current is seriously unbalanced, take measures to adjust it in time; Check whether the oil level of the transformer is normal and whether there is leakage. If any, replenish the oil as soon as possible to avoid the tap changer and coil exposed to moisture in the air.
(2) Regularly clean the dirt on the surface of distribution transformer bushing: check whether the bushing has flashover marks, whether the grounding is good, and whether the grounding lead has broken strands, desoldering and fracture; The grounding resistance detected with a megger shall not be greater than 4 .
(3) Reasonably select the wiring mode of low-voltage side conductor, such as copper aluminum transition clamp or terminal block. Apply conductive paste on the contact surface to increase the contact area and prevent heating and oxidation.
(4) According to the technical requirements of 10 / 0.4kV distribution transformer, a set of lightning arresters shall be installed at the high and low voltage sides close to the transformer.
(5) When switching the tap changer, the DC resistance values of the first and second times must be measured with an electric bridge, and records must be made to compare whether the three-phase DC resistance is balanced (the phase to phase difference is no more than 4%, and the line to line difference is no more than 2%). Compare the DC resistance value after switching with the previous records before switching, and put into operation after confirming that the switching is normal.
2
What Is the Difference Between Rectifier Transformer and Power Transformer
1 What is rectifier transformer
Converter is the general name of three working modes: rectifier, countercurrent and frequency conversion. Rectifier is the most widely used one. The characteristic of rectifier equipment is to output the input AC to DC after rectification and filtering. Rectifier transformer is the power transformer of rectifier equipment. Most industrial rectifier DC power supplies are obtained by rectifier transformer and rectifier equipment.
2 What is a power transformer
Power transformer generally refers to the transformer that supplies power to the electric drive system. Most of the transformers in the power grid are power transformers.
3 Difference between rectifier transformer and power transformer
(1) Functional difference
Functions of rectifier transformer: 1. Supply appropriate voltage to rectifier system; 2. It is to reduce the pollution of power grid caused by waveform distortion caused by rectifier system.
The output of rectifier transformer is still AC, which only provides power for rectifier equipment. Usually, the primary side is connected into a star shape and the secondary side is connected into an angle shape to suppress high-order harmonics. The secondary side is connected into an angle, and the neutral point is not grounded. When the rectifier equipment is grounded at one point, it will not cause equipment damage, and the grounding fault alarm signal will be sent through the grounding detection equipment. 1 Shielding isolation is added between the secondary.
Rectifier transformers are mainly used in electrolysis, smelting, excitation, transmission, cascade speed regulation, electrostatic dust removal and high-frequency welding. The structure is a little different. In order to make the waveform smooth, some rectifier transformers for electrolysis are made into six phase output, and a six phase rectifier bridge is added outside to get a relatively smooth waveform. According to the current waveform characteristics and anti harmonic requirements of thyristor rectifier circuit for smelting and high-frequency welding, the eddy current loss in rectifier transformer winding and stray loss in structural parts are optimized for some data and processes. In fact, the general structure is also similar.
The power transformer is usually Y / y connected neutral grounding (providing single-phase power supply). If it is used for rectifier equipment, the rectifier equipment will be damaged in case of grounding fault, and its ability to suppress high-order harmonics generated by rectifier equipment is also poor.
(2) Different uses
The transformer used as the power supply of rectifier is called rectifier transformer. Most of the rectifier DC power supply used in industry is obtained by the rectifier equipment composed of rectifier transformer and rectifier in AC power grid. In today's highly modern society, its great use can be seen directly or indirectly in almost every field. Power transformer is mainly used for power system, daily lighting and plant power. The main purposes of rectifier transformer are as follows:
1. Electrochemical industry;
2. DC power supply for traction;
3. DC power supply for transmission;
4. DC power supply for DC transmission;
5. DC power supply for electroplating or machining;
6. DC power supply for excitation;
7. DC power supply for charging;
8. DC power supply for electrostatic precipitator;
(1) Differences in address
Due to the close combination with the rectifier, the output voltage of the rectifier transformer is called valve side voltage, which is named because of the unidirectional conductivity of the diode.
(2) Differences in calculation methods
Due to the different waveforms of load current of rectifier, the calculation method of output current is not only very different from that of power transformer, but also different for different rectifier circuits.
4 Differences in design and manufacturing
![]()
Converter is the general name of three working modes: rectifier, countercurrent and frequency conversion. Rectifier is the most widely used one. The characteristic of rectifier equipment is to output the input AC to DC after rectification and filtering. Rectifier transformer is the power transformer of rectifier equipment. Most industrial rectifier DC power supplies are obtained by rectifier transformer and rectifier equipment.
2 What is a power transformer
Power transformer generally refers to the transformer that supplies power to the electric drive system. Most of the transformers in the power grid are power transformers.
3 Difference between rectifier transformer and power transformer
(1) Functional difference
Functions of rectifier transformer: 1. Supply appropriate voltage to rectifier system; 2. It is to reduce the pollution of power grid caused by waveform distortion caused by rectifier system.
The output of rectifier transformer is still AC, which only provides power for rectifier equipment. Usually, the primary side is connected into a star shape and the secondary side is connected into an angle shape to suppress high-order harmonics. The secondary side is connected into an angle, and the neutral point is not grounded. When the rectifier equipment is grounded at one point, it will not cause equipment damage, and the grounding fault alarm signal will be sent through the grounding detection equipment. 1 Shielding isolation is added between the secondary.
Rectifier transformers are mainly used in electrolysis, smelting, excitation, transmission, cascade speed regulation, electrostatic dust removal and high-frequency welding. The structure is a little different. In order to make the waveform smooth, some rectifier transformers for electrolysis are made into six phase output, and a six phase rectifier bridge is added outside to get a relatively smooth waveform. According to the current waveform characteristics and anti harmonic requirements of thyristor rectifier circuit for smelting and high-frequency welding, the eddy current loss in rectifier transformer winding and stray loss in structural parts are optimized for some data and processes. In fact, the general structure is also similar.
The power transformer is usually Y / y connected neutral grounding (providing single-phase power supply). If it is used for rectifier equipment, the rectifier equipment will be damaged in case of grounding fault, and its ability to suppress high-order harmonics generated by rectifier equipment is also poor.
(2) Different uses
The transformer used as the power supply of rectifier is called rectifier transformer. Most of the rectifier DC power supply used in industry is obtained by the rectifier equipment composed of rectifier transformer and rectifier in AC power grid. In today's highly modern society, its great use can be seen directly or indirectly in almost every field. Power transformer is mainly used for power system, daily lighting and plant power. The main purposes of rectifier transformer are as follows:
1. Electrochemical industry;
2. DC power supply for traction;
3. DC power supply for transmission;
4. DC power supply for DC transmission;
5. DC power supply for electroplating or machining;
6. DC power supply for excitation;
7. DC power supply for charging;
8. DC power supply for electrostatic precipitator;
(1) Differences in address
Due to the close combination with the rectifier, the output voltage of the rectifier transformer is called valve side voltage, which is named because of the unidirectional conductivity of the diode.
(2) Differences in calculation methods
Due to the different waveforms of load current of rectifier, the calculation method of output current is not only very different from that of power transformer, but also different for different rectifier circuits.
4 Differences in design and manufacturing
3
Internal Structure and Working Principle of Power Transformer
Power transformer is a static electrical equipment, which is used to change the AC voltage (current) of a certain value into another voltage (current) with the same frequency or several different values.
Transformer is a static electrical equipment used to transform AC voltage and current to transmit AC energy. It realizes electric energy transmission according to the principle of electromagnetic induction. Transformers can be divided into power transformers, test transformers, instrument transformers and transformers for special purposes: power transformers are necessary equipment for power transmission and distribution and power user distribution; The test transformer is used to conduct withstand voltage (step-up) test on electrical equipment; Instrument transformer is used for electrical measurement and relay protection of distribution system (PT, CT); Transformers for special purposes include furnace transformers for smelting, welding transformers, rectifier transformers for electrolysis, small voltage regulating transformers, etc.
Power transformer is a static electrical equipment, which is used to change the AC voltage (current) of a certain value into another voltage (current) with the same frequency or several different values. When the primary winding is connected with AC, alternating magnetic flux is generated. The alternating magnetic flux induces AC electromotive force in the secondary winding through the magnetic conduction of the iron core. The secondary induced electromotive force is related to the number of turns of the primary and secondary windings, that is, the voltage is directly proportional to the number of turns.
The main function is to transmit electric energy. Therefore, the rated capacity is its main parameter. Rated capacity is a customary value of power, which represents the size of transmitted electric energy, expressed in KVA or MVA. When the rated voltage is applied to the transformer, the rated current that does not exceed the temperature rise limit under specified conditions shall be determined according to it. The more energy-saving power transformer is amorphous alloy core distribution transformer. Its biggest advantage is that the no-load loss value is very low. Whether the no-load loss can be ensured is the core problem to be considered in the whole design process. When arranging the product structure, in addition to considering that the amorphous alloy core itself is not affected by external forces, the characteristic parameters of the amorphous alloy must be accurately and reasonably selected in the calculation.
A transformer is a static electric energy converter that transmits electric energy without changing its frequency.
Transformer is a large number of electrical equipment in the power system and plays a very important role. The total capacity of transformer is about 9 times that of generator. Its function is to increase or decrease the voltage of electric energy in the power system, so as to facilitate the rational transmission, distribution and use of electric energy.
In the power system, the higher the voltage, the smaller the current and the smaller the power loss on the transmission line; The cross-sectional area of the transmission line can also be reduced, which can reduce the metal consumption of the conductor.
Figure 1
Due to manufacturing difficulties, the generator voltage cannot be very high (below 20kV at present). Therefore, in the power plant, it is necessary to use step-up transformer to raise the generator voltage very high, so as to send a large amount of electric energy to distant power consumption areas, such as 35kV, 66kV, 110kV, 220kV, 330kV, 500kV, etc.
At the power load, the step-down transformer is used to reduce the voltage to an appropriate value for the user's electrical equipment. When the power transformer transmits electric energy, it also has some active power loss, but the number is small, so the transmission efficiency is very high. The efficiency of small and medium-sized transformers shall not be less than 95%, and the efficiency of large transformers can reach more than 98%.
2 Classification of power transformers
1. By function:
Power transformers are divided into step-up transformers and step-down transformers according to their functions. Step down transformers are used in plant substations. Step down transformer of terminal substation, also known as distribution transformer.
2. By capacity:
According to the capacity series, power transformers are divided into R8 capacity series and R10 capacity series.
R8 capacity series refers to that the capacity grade increases by R8 1.33 times. This series is adopted for the old transformer capacity grade in China, such as 100kVA, 135kva, 180KVA, 240kVA, 320kva, 420kva, 560kva, 750kva, 1000KVA, etc.
R10 capacity series means that the capacity grade is increased by multiple of R10 1.26. R10 series has dense capacity grade, which is convenient for reasonable selection and is recommended by IEC (International Electrotechnical Commission). This series is adopted for the new transformer capacity grade in China, such as 100kVA, 125kva, 160KVA, 200KVA, 250kVA, 315KVA, 400KVA, 500KVA, 630kVA, 800kVA and 1000KVA.
3. Divided by phase number:
Power transformers are divided into single-phase and three-phase according to the number of phases. Factory substations usually use three-phase power transformers.
4. According to voltage regulation mode:
According to the voltage regulation mode, power transformers are divided into on load voltage regulation (also known as off excitation voltage regulation) and on load voltage regulation. Most factory substations use no-load voltage regulating transformers.
5. According to winding structure:
According to the winding structure, power transformers include single winding autotransformer, double winding transformer and three winding transformer. Most factory substations use double winding transformers.
6. Classification by winding insulation and cooling mode:
Power transformers are divided into oil immersed, dry-type and inflatable (SF6) according to winding insulation and cooling mode. Oil immersed transformers include oil immersed self cooling type, oil immersed air cooling type, oil immersed water cooling type and forced oil circulating cooling type. Most factory substations use oil immersed self cooling transformers.
Figure 2
The so-called inflatable transformer refers to the transformer whose magnetic circuit (core) and winding are located in a shell filled with insulating gas. In the past, SF6 gas was generally used, so it is also called gas insulated transformer
7. By winding conductor material:
Power transformers are divided into copper winding transformers and aluminum winding transformers according to the material of winding conductors. In the past, aluminum winding transformers were mostly used in factory substations, but copper winding transformers with low loss have been more and more widely used.
![]()
Transformer is a static electrical equipment used to transform AC voltage and current to transmit AC energy. It realizes electric energy transmission according to the principle of electromagnetic induction. Transformers can be divided into power transformers, test transformers, instrument transformers and transformers for special purposes: power transformers are necessary equipment for power transmission and distribution and power user distribution; The test transformer is used to conduct withstand voltage (step-up) test on electrical equipment; Instrument transformer is used for electrical measurement and relay protection of distribution system (PT, CT); Transformers for special purposes include furnace transformers for smelting, welding transformers, rectifier transformers for electrolysis, small voltage regulating transformers, etc.
Power transformer is a static electrical equipment, which is used to change the AC voltage (current) of a certain value into another voltage (current) with the same frequency or several different values. When the primary winding is connected with AC, alternating magnetic flux is generated. The alternating magnetic flux induces AC electromotive force in the secondary winding through the magnetic conduction of the iron core. The secondary induced electromotive force is related to the number of turns of the primary and secondary windings, that is, the voltage is directly proportional to the number of turns.
The main function is to transmit electric energy. Therefore, the rated capacity is its main parameter. Rated capacity is a customary value of power, which represents the size of transmitted electric energy, expressed in KVA or MVA. When the rated voltage is applied to the transformer, the rated current that does not exceed the temperature rise limit under specified conditions shall be determined according to it. The more energy-saving power transformer is amorphous alloy core distribution transformer. Its biggest advantage is that the no-load loss value is very low. Whether the no-load loss can be ensured is the core problem to be considered in the whole design process. When arranging the product structure, in addition to considering that the amorphous alloy core itself is not affected by external forces, the characteristic parameters of the amorphous alloy must be accurately and reasonably selected in the calculation.
A transformer is a static electric energy converter that transmits electric energy without changing its frequency.
Transformer is a large number of electrical equipment in the power system and plays a very important role. The total capacity of transformer is about 9 times that of generator. Its function is to increase or decrease the voltage of electric energy in the power system, so as to facilitate the rational transmission, distribution and use of electric energy.
In the power system, the higher the voltage, the smaller the current and the smaller the power loss on the transmission line; The cross-sectional area of the transmission line can also be reduced, which can reduce the metal consumption of the conductor.
Figure 1
Due to manufacturing difficulties, the generator voltage cannot be very high (below 20kV at present). Therefore, in the power plant, it is necessary to use step-up transformer to raise the generator voltage very high, so as to send a large amount of electric energy to distant power consumption areas, such as 35kV, 66kV, 110kV, 220kV, 330kV, 500kV, etc.
At the power load, the step-down transformer is used to reduce the voltage to an appropriate value for the user's electrical equipment. When the power transformer transmits electric energy, it also has some active power loss, but the number is small, so the transmission efficiency is very high. The efficiency of small and medium-sized transformers shall not be less than 95%, and the efficiency of large transformers can reach more than 98%.
2 Classification of power transformers
1. By function:
Power transformers are divided into step-up transformers and step-down transformers according to their functions. Step down transformers are used in plant substations. Step down transformer of terminal substation, also known as distribution transformer.
2. By capacity:
According to the capacity series, power transformers are divided into R8 capacity series and R10 capacity series.
R8 capacity series refers to that the capacity grade increases by R8 1.33 times. This series is adopted for the old transformer capacity grade in China, such as 100kVA, 135kva, 180KVA, 240kVA, 320kva, 420kva, 560kva, 750kva, 1000KVA, etc.
R10 capacity series means that the capacity grade is increased by multiple of R10 1.26. R10 series has dense capacity grade, which is convenient for reasonable selection and is recommended by IEC (International Electrotechnical Commission). This series is adopted for the new transformer capacity grade in China, such as 100kVA, 125kva, 160KVA, 200KVA, 250kVA, 315KVA, 400KVA, 500KVA, 630kVA, 800kVA and 1000KVA.
3. Divided by phase number:
Power transformers are divided into single-phase and three-phase according to the number of phases. Factory substations usually use three-phase power transformers.
4. According to voltage regulation mode:
According to the voltage regulation mode, power transformers are divided into on load voltage regulation (also known as off excitation voltage regulation) and on load voltage regulation. Most factory substations use no-load voltage regulating transformers.
5. According to winding structure:
According to the winding structure, power transformers include single winding autotransformer, double winding transformer and three winding transformer. Most factory substations use double winding transformers.
6. Classification by winding insulation and cooling mode:
Power transformers are divided into oil immersed, dry-type and inflatable (SF6) according to winding insulation and cooling mode. Oil immersed transformers include oil immersed self cooling type, oil immersed air cooling type, oil immersed water cooling type and forced oil circulating cooling type. Most factory substations use oil immersed self cooling transformers.
Figure 2
The so-called inflatable transformer refers to the transformer whose magnetic circuit (core) and winding are located in a shell filled with insulating gas. In the past, SF6 gas was generally used, so it is also called gas insulated transformer
7. By winding conductor material:
Power transformers are divided into copper winding transformers and aluminum winding transformers according to the material of winding conductors. In the past, aluminum winding transformers were mostly used in factory substations, but copper winding transformers with low loss have been more and more widely used.
4
Use of Power Transformer
Transformer is the main equipment of substation, and its basic working principle is electromagnetic induction. At present, it is an indispensable part in our daily life.
Power transformer (transformer for short) is an electrical equipment used to change the AC voltage. According to the principle of electromagnetic induction, it exchanges one level of AC voltage with another level of AC voltage to meet the needs of different loads. Therefore, transformer plays a very important role in power system and power supply and consumption system.
The output voltage of the generator is usually 6.3kV, 10.5kv and no more than 20kV due to the limitation of the insulation level of the generator. It is difficult to carry out long-distance transmission with such a low voltage. Because when transmitting a certain power of electric energy, the lower the voltage, the greater the current, and most of the electric energy may be consumed in the resistance of the transmission line. Therefore, the step-up transformer can only be used to increase the terminal voltage of the generator to tens of thousands of volts to hundreds of thousands of volts, so as to reduce the transmission current and reduce the energy loss on the transmission line without increasing the conductor section to transmit the electric energy over a long distance.
After the transmission line transmits tens of thousands of volts or hundreds of thousands of volts of high voltage to the load area, the high voltage must be reduced to a low voltage suitable for electrical equipment through a step-down transformer. Therefore, in the power supply and consumption system, step-down transformers are needed to convert the high voltage transmitted by the transmission line into various levels of voltage to meet various composite needs.
Function of power transformer
1. Transmission and distribution of electrical energy. If it is a step-up transformer, it can send out electric energy. If it is a step-down transformer or distribution transformer, the electric energy can be transmitted or distributed respectively;
2. The rated voltage at the primary and secondary sides can be changed;
3. The phase angle of the primary and secondary sides can be changed;
4. Mainly the above items, of course, can also include: improving or protecting the role of the power grid, reducing or increasing the number of phases, etc.
Purpose of transformer
Current converter is a kind of transformer with closed core and no air gap. The advantage is that when the core is unsaturated, the waveform of the secondary current is the same as that of the primary side. The disadvantage is that it is easy to saturate and has poor linearity under the action of aperiodic component of current. Current converter is generally used in microcomputer protection. This equipment shall be used in the voltage forming circuit of input current by microcomputer protection device. The working principle is to convert the current into a linear DC voltage signal through impedance for use by the measuring circuit.
A transformer is an element that converts voltage. In our daily work, we often need to get voltages of different amplitudes, so we need to use transformers. For example, the voltage amplitude commonly used in our Chinese families is 220 V, that is to say, most household appliances are equipped with 220V voltage. For mobile phones used in our daily life, we need to reduce the voltage of 220V to a safe voltage relative to human body, which requires a transformer. In addition, when our students do some electrical experiments, for the sake of safety, we need to use a transformer to reduce the voltage to a safe voltage. When we transmit voltage, in order to reduce power loss, we need to use a transformer to increase the voltage.
The power transformer is composed of a closed iron core and two coils (also known as windings) wound around the iron core. One coil is connected to the power supply, which is called the primary coil (also called the primary coil); The other coil is connected to the load, which is called the secondary coil (also known as the secondary coil). Both coils are made of insulated wires, and the iron core is made of silicon steel sheets coated with insulating paint. With different turns of the coil, we can make various step-up transformers and step-down transformers to achieve different purposes.
Application of transformer in various aspects
There are many classifications of transformers. Different transformers are used in different places. as
Oil immersed distribution transformer is mainly applicable to pole erection, box type substation and distribution room and substation with separate distribution transformer room; Thousand type distribution transformer is mainly suitable for indoor distribution; The single-phase distribution transformer is easy to go deep into the load center for power supply because of its small volume and single pole erection. The single-phase distribution transformer has low loss and can supply power near the residential end, which greatly reduces the loss of low-voltage line, so it has also been widely used. Because some rural areas have the characteristics of small villages, few power users and relatively concentrated load, the use of transformers is very important. In rural areas, if a distribution transformer is needed for power supply, according to the existing load and development planning, we should consider that the distribution transformer should be installed in the center of the load as much as possible. For places with large population and large number of electricity users in rural areas, multiple distribution transformers are needed to supply power and distributed in different places, so as to achieve better power supply effect.
In the classification of transformers, there is a kind of transformer called box type, which is generally used in power engineering construction. According to the specific construction engineering requirements, it generally fluctuates between 102% 125% of the power consumption, so as to prevent the transformer from being burned out due to excessive voltage. Appropriate voltage switch shall be installed at the high-voltage end of the box transformer. The power consumption in the project construction shall be obtained through calculation at the high-voltage end. At the same time, voltage monitoring device and useless power compensation equipment with O.95 power coefficient shall be installed. In addition, it should be operated in strict accordance with the instructions.
Transformer type
There are many types of transformers, which can be classified according to voltage rise and fall, phase number, purpose, structure, cooling mode, etc.
Classified by voltage rise and fall: there are two types of step-up transformer and step-down transformer.
Classification by phase number: there are three types of single-phase transformer, three-phase transformer and multiple transformers.
Classification by purpose: there are power transformers used in power supply system; Instrument transformers (voltage transformers and current transformers) for measurement and relay protection; Pressure transformer for withstand voltage test of high voltage power supply equipment; There are special purpose transformers such as electric furnace transformer, welding transformer and rectifier transformer.
Classification by cooling mode and cooling medium: there are dry-type transformers cooled by air; Oil immersed transformer with oil cooling; There is a water-cooled transformer cooled by water.
The 21st century is an era of rapid development of high technology. Electricity is generally used in all aspects of people's life, so the status of transformer is becoming more and more important, especially the demand for electronic transformer is particularly strong. In daily life, the demand for low-voltage electronic transformers is relatively large. In other words, the development prospect of transformer is still relatively good. Therefore, it is necessary for us to have a certain understanding of the transformer. We should pay close attention to its principle, application and problems needing attention.
![]()
Power transformer (transformer for short) is an electrical equipment used to change the AC voltage. According to the principle of electromagnetic induction, it exchanges one level of AC voltage with another level of AC voltage to meet the needs of different loads. Therefore, transformer plays a very important role in power system and power supply and consumption system.
The output voltage of the generator is usually 6.3kV, 10.5kv and no more than 20kV due to the limitation of the insulation level of the generator. It is difficult to carry out long-distance transmission with such a low voltage. Because when transmitting a certain power of electric energy, the lower the voltage, the greater the current, and most of the electric energy may be consumed in the resistance of the transmission line. Therefore, the step-up transformer can only be used to increase the terminal voltage of the generator to tens of thousands of volts to hundreds of thousands of volts, so as to reduce the transmission current and reduce the energy loss on the transmission line without increasing the conductor section to transmit the electric energy over a long distance.
After the transmission line transmits tens of thousands of volts or hundreds of thousands of volts of high voltage to the load area, the high voltage must be reduced to a low voltage suitable for electrical equipment through a step-down transformer. Therefore, in the power supply and consumption system, step-down transformers are needed to convert the high voltage transmitted by the transmission line into various levels of voltage to meet various composite needs.
Function of power transformer
1. Transmission and distribution of electrical energy. If it is a step-up transformer, it can send out electric energy. If it is a step-down transformer or distribution transformer, the electric energy can be transmitted or distributed respectively;
2. The rated voltage at the primary and secondary sides can be changed;
3. The phase angle of the primary and secondary sides can be changed;
4. Mainly the above items, of course, can also include: improving or protecting the role of the power grid, reducing or increasing the number of phases, etc.
Purpose of transformer
Current converter is a kind of transformer with closed core and no air gap. The advantage is that when the core is unsaturated, the waveform of the secondary current is the same as that of the primary side. The disadvantage is that it is easy to saturate and has poor linearity under the action of aperiodic component of current. Current converter is generally used in microcomputer protection. This equipment shall be used in the voltage forming circuit of input current by microcomputer protection device. The working principle is to convert the current into a linear DC voltage signal through impedance for use by the measuring circuit.
A transformer is an element that converts voltage. In our daily work, we often need to get voltages of different amplitudes, so we need to use transformers. For example, the voltage amplitude commonly used in our Chinese families is 220 V, that is to say, most household appliances are equipped with 220V voltage. For mobile phones used in our daily life, we need to reduce the voltage of 220V to a safe voltage relative to human body, which requires a transformer. In addition, when our students do some electrical experiments, for the sake of safety, we need to use a transformer to reduce the voltage to a safe voltage. When we transmit voltage, in order to reduce power loss, we need to use a transformer to increase the voltage.
The power transformer is composed of a closed iron core and two coils (also known as windings) wound around the iron core. One coil is connected to the power supply, which is called the primary coil (also called the primary coil); The other coil is connected to the load, which is called the secondary coil (also known as the secondary coil). Both coils are made of insulated wires, and the iron core is made of silicon steel sheets coated with insulating paint. With different turns of the coil, we can make various step-up transformers and step-down transformers to achieve different purposes.
Application of transformer in various aspects
There are many classifications of transformers. Different transformers are used in different places. as
Oil immersed distribution transformer is mainly applicable to pole erection, box type substation and distribution room and substation with separate distribution transformer room; Thousand type distribution transformer is mainly suitable for indoor distribution; The single-phase distribution transformer is easy to go deep into the load center for power supply because of its small volume and single pole erection. The single-phase distribution transformer has low loss and can supply power near the residential end, which greatly reduces the loss of low-voltage line, so it has also been widely used. Because some rural areas have the characteristics of small villages, few power users and relatively concentrated load, the use of transformers is very important. In rural areas, if a distribution transformer is needed for power supply, according to the existing load and development planning, we should consider that the distribution transformer should be installed in the center of the load as much as possible. For places with large population and large number of electricity users in rural areas, multiple distribution transformers are needed to supply power and distributed in different places, so as to achieve better power supply effect.
In the classification of transformers, there is a kind of transformer called box type, which is generally used in power engineering construction. According to the specific construction engineering requirements, it generally fluctuates between 102% 125% of the power consumption, so as to prevent the transformer from being burned out due to excessive voltage. Appropriate voltage switch shall be installed at the high-voltage end of the box transformer. The power consumption in the project construction shall be obtained through calculation at the high-voltage end. At the same time, voltage monitoring device and useless power compensation equipment with O.95 power coefficient shall be installed. In addition, it should be operated in strict accordance with the instructions.
Transformer type
There are many types of transformers, which can be classified according to voltage rise and fall, phase number, purpose, structure, cooling mode, etc.
Classified by voltage rise and fall: there are two types of step-up transformer and step-down transformer.
Classification by phase number: there are three types of single-phase transformer, three-phase transformer and multiple transformers.
Classification by purpose: there are power transformers used in power supply system; Instrument transformers (voltage transformers and current transformers) for measurement and relay protection; Pressure transformer for withstand voltage test of high voltage power supply equipment; There are special purpose transformers such as electric furnace transformer, welding transformer and rectifier transformer.
Classification by cooling mode and cooling medium: there are dry-type transformers cooled by air; Oil immersed transformer with oil cooling; There is a water-cooled transformer cooled by water.
The 21st century is an era of rapid development of high technology. Electricity is generally used in all aspects of people's life, so the status of transformer is becoming more and more important, especially the demand for electronic transformer is particularly strong. In daily life, the demand for low-voltage electronic transformers is relatively large. In other words, the development prospect of transformer is still relatively good. Therefore, it is necessary for us to have a certain understanding of the transformer. We should pay close attention to its principle, application and problems needing attention.
5
How to Measure the Quality of Switching Power Transformer
Composition of switching power transformerThe main materials of switching power transformer: magnetic materials, conductor materials and insulating materials are the core of switching power transformer.Magnetic materials: the magnetic materials used in switching transformers are soft ferrite, which can be divided into MnZn system and NiZn system according to their composition and application frequency. The former has high permeability and high saturation magnetic induction, and has low loss in the medium and low frequency range. There are many shapes of magnetic cores, such as EI type, E type, EC type, etc.
Conductor material - Enamelled Wire: generally used for winding small electronic transformers, there are two kinds of enamelled wires: high strength polyester enamelled wire (QZ) and polyurethane enamelled wire (QA). According to the thickness of paint layer, it is divided into type 1 (thin paint type) and type 2 (thick paint type). The insulation coating of the former is polyester paint, which has superior heat resistance, insulation and electrical strength up to 60kV / mm; The insulation layer of the latter is polyurethane paint, which has strong self-adhesive and self welding performance (380 ), and can be welded directly without removing the paint film.
Pressure sensitive tape: the insulating tape has high electrical strength, convenient use and good mechanical performance. It is widely used in interlayer, group insulation and outsourcing insulation of switching transformer coils. The following requirements must be met: good viscosity, anti stripping, certain tensile strength, good insulation, good pressure resistance, flame retardant and high temperature resistance.
Skeleton material: the switch transformer skeleton is different from the general transformer skeleton. In addition to being the insulation and support material of the coil, it also undertakes the installation, fixation and positioning of the whole transformer. Therefore, the material for making the skeleton should not only meet the insulation requirements, but also have considerable tensile strength. At the same time, in order to bear the welding heat of the pins, It is required that the thermal deformation temperature of the skeleton material is higher than 200 , and the material must be flame retardant, with good processability and easy to be processed into various shapes
How to judge the quality of switching power transformer1. How to judge whether the switching power supply transformer is good or bad? Check whether there are obvious abnormalities by observing the appearance of the transformer. For example, whether the coil lead is broken, desoldered, whether the insulating material is burnt, whether the iron core fastening screw is loose, whether the silicon steel sheet is rusted, whether the winding coil is exposed, etc.2. How to judge the quality of switching power transformer and insulation test. Multimeter R 10K gear shall measure the resistance between iron core and primary, primary and secondary, iron core and secondary, electrostatic shielding layer and secondary and secondary windings respectively. The pointer of multimeter shall point to the infinity position. Otherwise, the insulation performance of the transformer is poor.
3. How to judge the quality of switching power transformer and the detection of coil on-off. Place the multimeter in R Gear 1: in the test, if the resistance value of a winding is infinite, it indicates that the winding has open circuit fault.Several detection methods of switching power transformerSeveral detection methods of switching power transformer are as follows:
1. Check whether there are obvious abnormalities by observing the appearance of the transformer. For example, whether the coil lead is broken, desoldered, whether the insulating material is burnt, whether the iron core fastening screw is loose, whether the silicon steel sheet is rusted, whether the winding coil is exposed, etc.2. Insulation test. Use the rx10k gear of the universal meter to measure the resistance values between the iron core and the primary, between the primary and each secondary, between the iron core and each secondary, between the electrostatic shielding layer and the secondary and each winding of the secondary. The pointer of the multimeter shall point to the infinity position. Otherwise, the insulation performance of the transformer is poor.3. Coil on-off detection. Put the multimeter in rx1. If the resistance value of a winding is infinite during the test, it indicates that the winding has open circuit fault.
4. Distinguish primary and secondary coils. The primary pin and secondary pin of the power transformer are generally led out from both sides, and the primary winding is mostly marked with the word 220V, while the secondary winding is marked with the rated voltage value, such as 15V, 24V, 35V, etc. Then identify according to these marks.
About Power Transformer Buying Guide
power transformer helps INGBO VILLE ENTERPRISE CO.,LTD. win a good reputation in the market. Regarding the product's production process, it is totally made by the state-of-the-art technology and completed by our professional technicians. One thing that should be emphasized that it has an attractive appearance. Supported by our strong design team, it is exquisitely designed. The other thing that should not be overlooked is it won't be released unless it withstands the strict quality test.
you might like
no data
Contact us
we welcome custom designs and ideas and is able to cater to the specific requirements. for more information, please visit the website or contact us directly with questions or inquiries.
no data
