What types of transformers are there and how to maintain them? Hengfengyou transformer
Writer： Hengfeng you electric Time：2023-03-24 views：times
Introduction: Transformer is a device that uses electromagnetic induction principle to change AC voltage. The main components are primary coil, secondary coil and iron core. The main functions are: voltage transformation, current transformation, impedance transformation, isolation, voltage stabilization, etc. There are many kinds of voltage transformers, which can be divided into single-phase transformer and three-phase transformer according to the number of phases; Dry type transformer and oil immersed transformer are classified according to cooling mode. What types of transformers are there? How to maintain it? Now let's have a detailed knowledge of Transformers with (the manufacturer).
1、 What is a transformer
A transformer is an electrical appliance that uses the principle of electromagnetic induction to transmit electrical energy or signals from one circuit to another. It is an important part of power transmission or signal transmission. A transformer is a device for converting AC voltage, current and impedance. When AC current flows through the primary coil, AC magnetic flux will be generated in the iron core (or magnetic core), thus inducing voltage (or current) in the secondary coil. The transformer is composed of iron core (or magnetic core) and coil. The coil has two or more windings. The windings connected to the power supply are called primary coils, and the remaining windings are called secondary coils. When the power transformer transmits power for a long distance, such as when the transmission power is constant, the lower the voltage is, the greater the current is, the larger the cross section of the conductor is, and the higher the laying cost is; If the step-up transformer is used to increase the voltage, the line current can be reduced, and the cost can also be reduced. After the high voltage is transmitted to the user center, it is necessary to reduce the high voltage into various voltages for users through step-down transformers. Therefore, transformers are very important electrical equipment.
2 Principle of transformer
A simple single-phase transformer consists of two electrical conductors. When some uncertain current (such as alternating current or pulse direct current) passes through one of the conductors, a variable magnetic field will be generated. According to the principle of electromagnetic mutual inductance, the changing magnetic field will produce potential difference in the second conductor. If the second conductor is part of a closed circuit, the closed circuit will generate current. Then transmit power. In ordinary transformers, the relevant electrical conductor is the coil (mainly copper wire), because the magnetic field generated by the coil is far greater than that of the straight wire. The principle is that the transformer is a device for converting AC voltage, AC current and impedance. When there is AC current in the primary coil, AC magnetic flux is generated in the iron core (or magnetic core), so that voltage (or magnetic core) is induced in the secondary coil. Or current).
The voltage VS and VP of the primary and secondary coils are proportional to the turns NS and NP of the two windings. As for the current or voltage ratio on both sides of the transformer, it depends on the turns of the circuit coils on both sides. The side with more turns has higher voltage and lower current, and vice versa. If leakage and other factors are excluded, the voltage ratio on both sides of the transformer is equal to the ratio of the turns of coils on both sides, that is, the voltage is proportional to the turns. Therefore, the turns ratio of the primary coil and the secondary coil can be reduced or increased, thereby increasing or decreasing the voltage. This characteristic of transformer makes it an important device for converting voltage. In addition, apart from the leakage factor, since the transformer follows these two laws, it will not be an amplifier. If the voltage on both sides of the transformer is different, the current flowing through both sides of the transformer will also be different, and the difference between the two is inversely proportional. If the current on one side of the transformer is less than that on the other side, the voltage on the side with less current is greater; vice versa. However, the power consumed on both sides of the transformer (i.e. the product of voltage and current on one side) should be equal.
3、 Type of transformer
According to the number of phases:
1) Single phase transformer: used for single-phase load and three-phase transformer bank.
2) Three phase transformer: used to raise and lower the voltage of three-phase system.
2. By cooling mode:
1) Dry type transformer: natural cooling or fan cooling depending on air convection, mostly used in high-rise buildings, high-speed toll stations, local lighting, electronic circuits and other small capacity transformers.
2) Oil immersed transformer: relying on oil as the cooling medium, such as oil immersed self cooling, oil immersed air cooling, oil immersed water cooling, forced oil circulation, etc.
3. By use:
1) Power transformer: used for voltage rise and fall of power transmission and distribution system.
2) Transformer: such as voltage transformer, current transformer, measuring instrument and relay protection device.
3) Test transformer: generate high voltage and conduct high voltage test on electrical equipment.
4) Special transformers: such as furnace transformer, rectifier transformer, regulating transformer, capacitor transformer, phase shifting transformer, etc.
4. According to winding form:
1) Double winding transformer: used to connect two voltage levels in the power system.
2) Three winding transformer: generally used for substations in power system areas, connecting three voltage levels.
3) Autotransformer: used to connect power systems with different voltages. It can also be used as a common step-up or step-down transformer.
5. According to the form of iron core:
1) Iron core transformer: high-voltage power transformer.
2) Amorphous alloy transformer: Amorphous alloy iron core transformer is a new type of magnetic conductive material, with no-load current reduced by about 80%. It is a kind of distribution transformer with ideal energy-saving effect, especially suitable for rural power grid and developing areas. Lower place.
3) Shell type transformer: special transformer for large current, such as furnace transformer and welding transformer; Or power transformers for electronic instruments, televisions, radios, etc.
4、 Special parameters of transformer
The iron loss of the operating frequency transformer has a great relationship with the frequency, so it should be designed and used according to the operating frequency.
This frequency is called the operating frequency. Under the specified frequency and voltage, the rated power of the transformer can work for a long time without exceeding the output power of the specified temperature rise.
Rated voltage refers to the voltage allowed to be applied by the transformer coil, which shall not be greater than the specified value during operation.
The voltage ratio refers to the ratio of the primary voltage to the secondary voltage of the transformer. The no-load voltage ratio is different from the load voltage ratio.
When the secondary of no-load current transformer is open circuit, there is still a certain current in the primary, which is called no-load current. No load current consists of magnetizing current (magnetic flux generated) and iron loss current (caused by iron loss). For a 50Hz power transformer, the no-load current is basically equal to the excitation current. No load loss refers to the power loss measured at the primary when the secondary of the transformer is open circuit. The main loss is the core loss, followed by the loss (copper loss) caused by the no-load current on the copper resistance of the primary coil, which is very small. Efficiency refers to the percentage of the ratio of secondary power P2 to primary power P1. Generally, the higher the rated power of transformer, the higher the efficiency.
The insulation resistance represents the insulation performance between transformer coils and between coils and iron core. The insulation resistance is related to the performance, temperature and humidity of the insulating materials used.
5、 Transformer capacity
Transformer capacity class: 30, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300, 8000, 10000, 12500, 16000, 20000, 25000, 31500, 40000, 50000, 63000, 90000, 120000, 150000, 180000, 260000, 360000, 400000kVA. Generally, 630KVA and below capacity transformers are collectively referred to as small transformers; 800~6300KVA transformers are called medium transformers; 8000~63000KVA transformers are called large transformers; 90000KVA and above are called extra large transformers.
The selection of transformer capacity has a great influence on the comprehensive investment benefit. If the transformer capacity is too large, there will be a "big horse pulling the small car" phenomenon, which not only has a large one-time investment, but also has a large no-load loss. infeasible. The optimal load rate of the transformer (that is, the load rate at the highest efficiency) is not in the rated state, but between 40% and 70%. If the load rate is too high, the loss will increase significantly; On the other hand, due to the small capacity and margin of the transformer, the load will increase slightly, so it is necessary to replace the box type transformer with large capacity. Frequent capacity expansion is bound to increase investment and affect power supply. The selection of transformer capacity shall be based on the existing load, and the load development shall be properly considered. The selection of voltage transformer capacity can be determined according to the five-year power development plan.
6、 Common Mistakes in Transformer Selection
1. As long as the products are produced by famous manufacturers, they must not be inferior transformers
Famous brand manufacturers do have certain advantages in the industry competition due to brand, technology, capital and other reasons. But that is for some 110KV and 220KV products. Due to the high entry threshold, ordinary small power distribution manufacturers have no strength to produce such products. However, for 10KV transformers, any company that produces transformers can do so, and some small manufacturers have more advantages than large companies to some extent due to process, region, after-sales and other factors. For example, a transformer factory in Hubei won the bid in the bidding business of China Southern Power Grid in December 2011, but when sampling the products it supplied, most of its products were inferior products of half copper and half aluminum, which led to the loss of China Southern Power Grid. Qualified bidding qualification.
2. As long as the price is low, the choice is good in quality and low in price, but there is also a view that "cheap is not good". Therefore, I suggest the customer not only consider the price when purchasing the transformer, but choose multiple manufacturers for comparison and make a final decision after multiple analysis. Another suggestion is that customers should go to their product manufacturers to check their products, production process, factory inspection and other procedures, so that they can have a bottom line.
3. I was blinded by the manufacturer's verbal promises. In order to attract customers, I made some promises such as "life-long maintenance", "one-year replacement", and "absolute copper" during the negotiation. However, when I bought the product, I did not write these promises in the contract, which would lead to the manufacturer refusing to accept the account after the product has problems. Therefore, any commitment must be written in order to protect the interests of customers as much as possible.
7、 Maintenance method of transformer (manufacturer)
Allowable temperature
When the transformer is running, its coil and iron core will produce copper loss and iron loss, which will become heat energy and raise the temperature of the transformer core and coil. If the temperature exceeds the allowable value for a long time, the insulation will gradually lose its mechanical elasticity, leading to insulation aging. When the transformer is running, the temperature of each part of the transformer is different. The coil temperature is the highest, followed by the core temperature. The temperature of insulating oil is lower than that of coil and iron core. The upper oil temperature of the transformer is higher than the lower oil temperature. The allowable temperature of the transformer during operation shall be checked according to the upper oil temperature. For Class A insulated transformer in normal operation, when the ambient air temperature reaches 400 ℃, the limiting operating temperature of the transformer winding is 1050 ℃. Since the winding temperature is 100C higher than the oil temperature, it is stipulated that the upper oil temperature of the transformer shall not exceed 950C to prevent the oil from deteriorating.
In general, the oil temperature should not exceed 850C to prevent the insulation oil from being oxidized. For transformers with forced oil circulating water cooling and air cooling, the upper oil temperature shall not often exceed 750 ℃. (The maximum allowable value of the upper oil temperature of the transformer is 800C) 2. The allowable temperature rise monitors the upper oil temperature during the operation of the transformer. Elevator. The difference between transformer temperature and ambient air temperature is called transformer temperature rise. For Class A insulated transformer, when the maximum ambient temperature is 400C, the national standard stipulates that the winding temperature rise is 650C, and the allowable oil temperature rise is 550C. As long as the temperature rise of the transformer does not exceed the specified value, it can ensure the safe operation of the transformer within the specified service life under the rated load. (The transformer can operate continuously with rated load for 20 years during normal operation) 3. The power load of the transformer shall be about 75-90% of the rated capacity of the transformer during normal operation with reasonable capacity.
These are the types of transformers and how to maintain them? To learn more, we can pay attention to Hengfengyou Electric, which focuses on manufacturing and exporting various distribution transformers, rectifier transformers, furnace transformers and mining transformers, and has been exported to more than 30 countries and regions around the world, including Uzbekistan, Kazakhstan, Pakistan, Kuwait, Iraq, the United Arab Emirates, Zimbabwe, Tanzania, South Africa, the United States, Spain, etc. With 30 years of power transformer manufacturing and sales experience, Hengfengyou Electric will provide you with the best electrical product solutions, www.hengfengyou com ； info@hengfengyou.com ； WhatsApp：+86158 5325 2696（Jack） +86158 5326 5269（Alisa）
