| Application: | Power, Instrument, Lighting, Rectifier, Power Grid, Power Station, Substation |
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| Phase: | Three |
| Core: | Core-type Transformer |
| Cooling Method: | Dry-type Transformer |
| Winding Type: | Two-winding Transformer |
| Certification: | ISO9001-2000, ISO9001, CCC, CE |
| Samples: |
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| Customization: |
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Suppliers with verified business licenses
Audited Supplier Generator excitation transformer
1, Introduction
Usually connected to the generator outlet, a step-down transformer is required due to the high output voltage of the generator and the low rated voltage of the excitation system.
The safe and stable operation of the excitation transformer used in the generator is a prerequisite for the safe and stable operation of the self parallel excitation unit, a prerequisite for stable and full load power generation of the generator unit, and a key to the reliable operation of the excitation system.
The required electrical power for the excitation system is obtained from the generator outlet. The function of the excitation transformer is to reduce the generator outlet voltage (22kV) to the input voltage of the power thyristor (850V), provide electrical isolation between the generator terminal and the excitation winding, and also serve as the rectification impedance of the power thyristor.
2, The form and characteristics of excitation transformers
Excitation transformers are mainly divided into four types according to insulation methods
(1) Epoxy resin cast dry-type transformer.
(2) Alkali free fiberglass winding immersed dry-type transformer.
(3) MORA type dry-type transformer.
(4) Oil immersed transformer.
Oil immersed transformers are traditional transformers that are gradually being replaced by dry-type transformers.
Dry type transformers have superior performance in fire prevention, explosion prevention, and environmental protection, making them the mainstream application of excitation transformers.
The world's first epoxy dry-type transformer was manufactured by West German company AEG in 1964.
The characteristics of epoxy resin cast dry-type transformers:
(1) High insulation strength, epoxy resin used for casting has an insulation breakdown field strength of 18-22kV/mm, and oil immersed transformers with the same voltage level have roughly the same lightning impulse strength.
(2) Strong short-circuit resistance.
(3) Outstanding disaster prevention performance, epoxy resin is flame retardant and can self extinguish, without causing explosions.
(4) Excellent environmental performance, epoxy resin moisture-proof and dustproof, can operate under harsh environmental conditions.
(5) Low maintenance workload.
(6) Low operating loss, high operating efficiency, and low noise.
(7) Small size, light weight, convenient installation and debugging
The characteristics of MORA type dry-type transformers are as follows:
(1) MORA dry-type transformer is a new type of transformer developed by MORA Transformer Factory in Germany in the past decade to adapt to new environmental concepts and apply new processes and materials.
(2) The high-voltage winding of MORA type dry-type transformer is layered and flat wound on a ceramic insulation bracket with good insulation performance. There are cooling air ducts in both the longitudinal and transverse directions between the high and low voltage windings, and the transformer has good short-term overload and short-circuit resistance.
(3) The MORA type dry-type transformer immerses the winding in composite insulation paint under vacuum and then dries it, which is a simple process.
(4) The insulation of transformer windings is composed of glass fiber or NOMEX paper, achieving F or H insulation level.
(5) MORA type has good flame retardant properties.
(6) MORA type can be disassembled after failure. The winding material can be recycled.
(7) The MORA type does not require pouring equipment and molds, which can greatly save initial investment and provide greater flexibility in product design.
(8) The MORA type has a slightly larger workload for operation and maintenance, and repairs are relatively easy.
At present, epoxy resin cast transformers are mostly used in Europe and Asia, while MORA type transformers are more commonly used in the United States.
The dry reference impact level of epoxy resin casting can reach 250kV, MORA type is 150kV.
The maximum capacity of epoxy resin cast dry-type transformers can reach 20MVA, The MORA type can only reach 8-10 MVA. [1]
3, General requirements for excitation transformers
The excitation power rectifier of the generator using self parallel excitation method is powered by the excitation transformer. The high voltage side of the excitation transformer is usually connected to the generator terminal bus, and the low voltage side is connected to a three-phase fully controlled bridge rectifier with thyristors. The load of the excitation power divider is a generator with high inductance and insulation to ground. The characteristics of the load and wiring of the excitation transformer, as well as the specific requirements of the power grid and power plant for the generator excitation system, make the working conditions and technical requirements of the excitation transformer of the self parallel excited hydro generator not completely the same as those of the general application of power transformers, mainly including the following aspects.
(1) The winding current of the excitation transformer is non sinusoidal, and the design of the transformer needs to consider the influence of harmonic currents in the winding. Due to the fact that the time constant of the generator rotor is usually several seconds, the thyristor current of the excitation power rectification device and the line current on the AC side (i.e. the low-voltage side of the excitation transformer) are both considered as rectangular waves, with fundamental and harmonic components present. The harmonic current will increase the copper and iron losses of the transformer and cause distortion of the voltage waveform at the generator end. Therefore, when designing and manufacturing excitation transformers, it is necessary to consider the impact of harmonic currents in the transformer windings, including the magnetic density, capacity, overload capacity, etc. of the transformer's iron core. Harmonic current may cause harmonic noise during transformer operation, so measures to reduce harmonic noise need to be considered in the structure and mechanical strength of the iron core and winding.
(2) As an excitation transformer connected to the generator end, it needs to be designed according to the technical requirements of the electrical equipment at the generator end. According to the requirements of GB 1094.1 "General Principles of Power Transformers Part 1", the terminals connected to the transformer and generator should be able to withstand 1.4 times the rated voltage for 5 seconds when the generator is under load. Usually, it is still required to operate for 60 seconds under an overvoltage of 1.3 times the rated voltage at the generator terminal. The excitation transformer should be able to operate continuously for a long time at 110% of the rated voltage.
(3) The rated voltage of the low-voltage winding of the excitation transformer should be designed and selected according to the requirements of the excitation peak voltage when the generator is subjected to strong excitation. When the generator is forcibly excited, there is a highest requirement for the output voltage of the excitation power rectifier, which is the excitation peak voltage of the generator. The excitation peak voltage is selected according to the requirements of the power system where the generator is located.
(4) The transformer capacity should be able to meet the excitation capacity required for long-term continuous operation of the generator. When the excitation current and voltage of the generator are 1.1 times the rated load excitation current and voltage of the generator, it can operate continuously for a long time.
(5) The overload capacity of the excitation transformer should meet the requirements of the excitation capacity and duration of the generator's strong excitation. When the excitation transformer is subjected to strong excitation of the generator, the generator operates under the excitation peak voltage, and the steady-state value of the excitation current is also the excitation peak current. At this time, the excitation power has the highest requirement for the load capacity of the excitation transformer.
(6) Static isolation shielding and grounding should be installed between the high-voltage and low-voltage windings of the excitation transformer. When the transformer is put into operation and transient overvoltage occurs on the high-voltage side, overvoltage will be generated on the low-voltage winding of the excitation transformer through the distributed capacitance between the high-voltage and low-voltage windings of the excitation transformer. To reduce the overvoltage on the low-voltage side of the excitation transformer at this time, static shielding should be installed between the high-voltage and low-voltage windings of the excitation transformer and grounded together with the transformer core to avoid overvoltage threatening the safety of the excitation power rectifier. Static shielding can also reduce the impact of high-order harmonics and overvoltage on the low-voltage winding of transformers on the high-voltage winding and power grid, and improve excitation
4, Electromagnetic compatibility of magnetic transformers.
In addition, as an application category of power transformers, excitation transformers still need to meet the technical requirements of general power transformers. Mainly including the following aspects:
(1) Operating temperature rise and insulation heat resistance level.
(2) Ability to withstand short circuits.
(3) Insulation level.
(4) No requirements for auxiliary equipment, including current transformers, temperature monitoring equipment, etc.
(5) Other factors include noise level, partial discharge level, and three-phase symmetry.
5, There are still some engineering related technical requirements for excitation transformers in practical engineering applications, such as:
(1) Type and structure of excitation transformer.
(2) Assembly method and protection level.
(3) The installation method and requirements at the power plant site, including the connection to the generator busbar, etc.
For the convenience of transportation or suitable connection with the generator's phase separated enclosed busbar, large generator excitation transformers usually adopt the structure of single-phase transformers forming three-phase transformer groups, and require single-phase transformers to have the same structure and good interchangeability.
6, Structure and Design of Excitation Transformers
The following is an example of an epoxy resin cast dry-type transformer.
core
The iron core is the magnetic circuit of a transformer, composed of silicon steel sheets and clamping devices. The calcium core material is made of high-quality cold-rolled grain oriented silicon steel sheets, with a 45 ° fully inclined seam structure. The core rod is wrapped with insulation tape and sealed with special resin on the surface. The iron core must be grounded at a point, otherwise it will form a circulating current and increase losses. The no-load loss of transformers is mainly due to the loss of the iron core.
The main measures to reduce the no-load loss of transformers are:
Reduce the magnetic flux density of transformer cores;
Select high-quality iron core silicon steel sheet materials;
Reduce the thickness of the iron core plate
Adopting a fully inclined seam structure.
winding
The winding is the most important component of a dry-type transformer, mainly composed of wires (copper wire) and insulation structure (resin).
The structure of the winding determines the rated capacity, rated voltage, and operating conditions.
The load loss of a transformer consists of resistance loss and additional losses in the winding wires. The calculation of windings should meet the following requirements:
(1) Electrical strength. The insulation of the winding must meet the requirements of national standards or user requirements for power frequency and lightning impulse test voltage, and leave a certain margin.
(2) Heat resistance strength. Under load operation, the temperature rise of the winding shall not exceed the temperature rise limit specified by the insulation material's heat resistance level.
(3) Mechanical strength. The electric force generated by the winding of a dry-type transformer under the action of short-circuit current will cause displacement of the winding and changes in short-circuit impedance, both of which should meet the requirements of national standards.
For cast dry-type transformers. The high-voltage winding is poured with resin in the mold, and the ends of the low-voltage winding are encapsulated with resin.
The winding materials are mainly copper and aluminum. Based on the physical properties of the resin system and conductive materials themselves, the thermal expansion coefficient of the resin system filled with glass fiber filaments is similar to that of copper. Therefore, copper conductors are commonly used in dry-type transformers filled with glass fiber filaments. The thermal expansion coefficient of resin system filled with silicon micro powder is similar to that of aluminum, so aluminum conductors are commonly used in dry-type transformers filled with silicon micro powder. Aluminum winding dry-type transformers have shortcomings such as poor mechanical strength and high requirements for welding quality.
There are two main types of conductors used for transformer windings: linear and foil.
The winding types mainly include layer winding and foil winding.
The high-voltage winding technology is mature, the insulation quality is reliable, the degree of automation is high, and the usage rate is over 70%.
Low voltage foil winding has high work efficiency, saves materials, less magnetic leakage, strong short-circuit resistance, and a usage rate of over 90%.
7, Selection of excitation transformer
In terms of design and structure, excitation transformers, like ordinary distribution transformers, have a short-circuit voltage of 4% to 8%. Considering that the excitation transformer must be reliable, it must have a certain overload capacity during strong excitation. And the excitation power supply is generally not designed as a backup power supply, so it is advisable to choose a dry type transformer with simple maintenance and strong overload capacity. In terms of reducing the cost of excitation systems, using oil immersed transformers is also feasible.
When the excitation transformer is installed outdoors, the feeder line from the transformer side to the rectifier bridge should not be too long due to the reactance voltage drop, especially in the case of high excitation current, which must be considered. It is not advisable to use single core armored cables. Instead, rubber cables should be used. Because when a single core armored cable is powered by AC, it will sense a higher voltage and an undeniable current in the steel armor, causing interference to the communication cable.
Excitation transformer performance and wiring. The performance and wiring requirements of the excitation transformer should be clearly defined, such as type, rated capacity (meeting the requirements of the excitation system), temperature rise, insulation and voltage resistance requirements, three-phase group wiring of the transformer, insulation level, noise level, and partial discharge level.
Technical requirements. Clarify the detailed technical requirements for excitation transformers. In the selection process, some hydropower plants require excitation transformers to use products from well-known domestic manufacturers.
For units that use electrical braking for shutdown, it is necessary to clarify whether the excitation transformer also serves as a braking transformer.
Shanghai Zhiyou Electric Manufacturing Co., Ltd., established in 2007, is a professional manufacturer of power transformers in China and a leading large-scale manufacturer of transformers in China. It specializes in the production of transformers, and its products are widely used in power transmission and distribution, various power stations, etc. The company is located in Shanghai, the economic center of China, an international metropolis. It has standardized production workshops and the most advanced transformer production and manufacturing technology today. Shanghai Zhiyou has obtained ISO9001 international quality management system certification, ISO14001 international environmental management system certification, and EU CE certification, and has independent patents and trademarks. All products have passed the testing and certification of Chinese national authoritative institutions, and have obtained type test certificates. Corporate honor, awarded as a "Famous Brand in China" by the authoritative organization China Enterprise Quality Certification and Supervision Center. The quality of the products produced by the company is reliable, and the product standards are in line with or higher than the Chinese national standards and international general standards. They are highly praised by the Chinese and international markets.
The company continuously learns and introduces the latest and most advanced manufacturing technology and design concepts from both domestic and international sources, with a comprehensive quality system, strict raw material and product quality inspection, and high-quality pre-sales and after-sales services, effectively ensuring product quality and reliability. It provides customers with high-quality products, establishes customers' confidence in the Shanghai Zhiyou brand, and enjoys a good reputation in both domestic and foreign markets.
Shanghai Zhiyou Electric Manufacturing Co., Ltd. is currently seeking globally trusted partners as our agents in various regions. If you trust our products, please contact us through Made in China website or directly by email. We will reply to you as soon as we receive the information.
| Transformer Type | Dry type transformer, Oil Immersed Distribution Transformer |
| Rated Capacity | 50~8000kVA/Customized |
| Rated Voltage(HV/LV) | up to 35kV/Customized |
| Frequency | 50 Hz/60 Hz |
| Impedance | 4~6% |
| Cooling Way | ONAN/ONAF/Customized |
| Tapping Range | +2X2.5%/-2X2.5%/Customized |
| Vector Group | Dyn11/Customized |
| Winding Material | Copper/Aluminium |
| Core Materials | Silicon Steel |
| Insulation Level | as Per IEC Standard |
| Temperature Rise | Customized |
| Accessories | Fans, Enclosure |
| Optional Protective Enclosure | IP00/IP20/IP23/Cutomized |
| Lightning Impulse Withstand Voltage | as Per IEC Standard |
| Transport Package | Wooden Pallet, Wooden Case |
| Manufacturer | Shanghai Zhiyou Electric Manufacturing Co., Ltd |
| Winding Type | Two-winding |
Ambient conditions for Conventional transformers using:
- Ambient temperature: Maximum +40ºC,Minimum -25ºC
- Relative humidity: At 25ºC, not higher than 95% for daily average humidity and not higher than 90% for monthly average ambient temperature.
- Altitude: less than 2000 meters.
- Seismic level: less than 3m/s2 at horizontal direction and less than 1.5m/s2 at vertical direction.
- Installation environment: No obvious and heavy pollution, no explosive and corrosive gas and dust, with good air ventilation and no severe vibration and shock.
(Note: if the application environment is different from the above standard service conditions, please contact us for customized designs.)
Advantage:
- Low loss, low noise, low partial discharge, high reliability
- Powerful anti-short circuit capacity, high anti-lightning impulse capacity
- HV coil is Vacuum casted with epoxy resin with pressure, capabilities for better the cast without pressure.
- Simulating analys is being used in the core model, the resonance can be avoided and the noise is reduced.
- Simulation calculation and analysis of lightning impulse wave are applied to HV Coils; anti-lightning impulse capability is improved.
Manufacture Technology
Core:
- Our transformer's core is made of high quality cold rolled grain oriented silicon steel sheet with high magnetic permeability. It is using full 45° slope lamination, so that the noload loss and the no-load current are reduced efficiently.
LV Winding:
- LV windings are adopting superior foil conductors or made of 100% copper wire, thus to obtain better amperturn balance and reduce more transverse magnetic flux leakage. Then to greatly improves transformer's anti-short circuit capability.
- Excellent design of oil passage structure, greatly increasing the coils' heat dispersion effect. It helps to decrease temperature rise of the LV winding and improve transformers' overload capability.
HV Winding
- HV windings are made of superior copperconductor wires. Adopting fiberglass to reinforced insulation.
- HV windings are adopted optimized structure to improve transformer's distribution of electric field.
- We use our existing technology calculate and analysis Lightning wave process simulation. Then substantially improving product's antilighting capability.
Insulation construction:
- Aclass level Insulation construction. The high-voltage coil and low-voltage coil are placed with the same center. Between the coils, use the thin paper cylinder with little oil clearance construction.
Tank:
- The tank is jointed with highquality steel. The surface is eliminated rust phosphate coating and painted with the type of FVC anticorrosive paint. It has ability to prevent the corrosion from oil and chemical matter. It can be broadly applied to outdoors with bad environment for its contour artistic, easily installation and maintenance free.
Components:
- All the power transformers equipped with highvoltage bushing, low-voltage bushing, oil-relesase valve earthling boilt, lifting board, name plate, pressure vale and so on. The transformers which are over 800kVA are equipped with signal thermometer and gas relay.
Shanghai Zhiyou Electric Manufacturing Co., Ltd.
Shanghai Zhiyou Electric Manufacturing Co., Ltd., established in 2007, is a professional manufacturer of power transformers in China and a leading large-scale manufacturer of transformers in China. It specializes in the production of transformers, and its products are widely used in power transmission and distribution, various power stations, etc. The company is located in Shanghai, the economic center of China, an international metropolis. It has standardized production workshops and the most advanced transformer production and manufacturing technology today. Shanghai Zhiyou has obtained ISO9001 international quality management system certification, ISO14001 international environmental management system certification, and EU CE certification, and has independent patents and trademarks. All products have passed the testing and certification of Chinese national authoritative institutions, and have obtained type test certificates. Corporate honor, awarded as a "Famous Brand in China" by the authoritative organization China Enterprise Quality Certification and Supervision Center. The quality of the products produced by the company is reliable, and the product standards are in line with or higher than the Chinese national standards and international general standards. They are highly praised by the Chinese and international markets.
The company continuously learns and introduces the latest and most advanced manufacturing technology and design concepts from both domestic and international sources, with a comprehensive quality system, strict raw material and product quality inspection, and high-quality pre-sales and after-sales services, effectively ensuring product quality and reliability. It provides customers with high-quality products, establishes customers' confidence in the Shanghai Zhiyou brand, and enjoys a good reputation in both domestic and foreign markets.
Shanghai Zhiyou Electric Manufacturing Co., Ltd. is currently seeking globally trusted partners as our agents in various regions. If you trust our products, please contact us through Made in China website or directly by email. We will reply to you as soon as we receive the information.
Our Best Service For You
1. Pre sale service
a. make technical solution
b. send quotation, technical data sheet and drawing
c. prepare power transformer plan, testing plan and shipment plan
2. In sale service
a. supervise the manufacturing schedule totally in accordance with the plan
b. send photos to customer during every manufacturing process(hold point)
c. inform the customer one week before testing.
3. After sale service
a. installation and commissioning, training the workers
b. quick response within 12 hours any time
c. provide 12 months guarantee period normally.
Q1: Are you a factory or trading company?
A1: We are a factory, and we can guarantee our price is first-hand very cheap and competitive. Our factory is in Shanghai, the international metropolis of China.
Q2: What is the payment term?
A2: T/T, L/C or negotiation.We accept T/T 30% deposit and 70% balance payment, the balance should be paid after acceptance before shipment.
Q3: Do you have any Certificate?
A3: Yes. Our transformers have CE certificates, type test reports tested by national authoritative institutions, and certificates of conformity.
Q4: Could I have the prices of your products?
A4: Welcome. Please feel free to send us an inquiry here. We will reply to you within 24 hours.
Q5: How about the delivery time?
A5: My friends, when you confirm the order, there will be about 25 to 45 days to produce which depends on your delivery plan and our order arrangements.
Q6: May I know the warranty time?
A6. We offer 12 months warranty time for the transformer quality. For any questions about our products, you can consult our sales manager any time and anywhere. We will provide the professional assistance to you.
Q7: Do you accept product customization?
A7: Yes of course. Please provide specific drawings or parameters we will quote you after evaluation.
Q8: Would you accept using customer's logo?
A8: Yes, we can provide OEM and ODM service.
Q9: What is the standard of package?
A9: Export standard package or special package according to customer's requirement.
Q10: How can we trust you?
A10: As an enterprise specializing in transformer production for 17 years, Shanghai Zhiyou Electric has high quality, fast delivery, guarantee after-sales service and factory price.We have more than 17 years manufacturing and R&D experience, and cooperated with many customers all over the world. We have many patent certificates, test report, ISO9001, ISO14000 certificate. We are the audited supplier of Made-In-China.
Q11: How do you conduct quality control in your factory?
A11: Shanghai Zhiyou Electric transformers are manufactured in accordance with international standards (such as IEC, SGS, Intertek, CE and other international certifications) and customer requirements . All transformers are 100% conducted routine test, type test and special test before delivery to ensure every product is qualified.
Q12: I have great trust in Shanghai Zhiyou's transformer products and would like to become your company's general agent in our country. How can I proceed?
A12: Thank you for your recognition of Shanghai Zhiyou Company's products. Shanghai Zhiyou Electric Manufacturing Co., Ltd. is currently seeking globally trusted partners as our agents in various regions. Please contact us through Made in China website or directly by email. We will reply to you as soon as we receive the information.
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