Dry-type transformers rely on air convection for natural cooling or increased fan cooling and are mostly used for small-capacity transformers such as high-rise buildings, high-speed toll station electricity, local lighting, and electronic circuits.
Transformers can convert electrical energy into high-voltage and low-current forms and then convert it back, greatly reducing the loss of electrical energy in the transmission process, making the economical transmission distance of electrical energy farther.
The transformer is a static electrical appliance made by the principle of electromagnetic induction and used to change the AC voltage. The main components are the primary coil, secondary coil, and iron core (magnetic core).
The main functions are voltage transformation, current transformation, impedance transformation, isolation, voltage stabilization (magnetic saturation transformer), etc. It can be divided into power transformers and special transformers (electric furnace transformer, rectifier transformer, power frequency test transformer, voltage regulator, mining transformer, audio transformer, intermediate frequency transformer, high-frequency transformer, impact transformer, instrument transformer, electronic transformer), Reactors, transformers, etc.).
In the generator, whether the coil moves through the magnetic field or the magnetic field moves through the fixed coil, the electric potential can be induced in the coil. In both cases, the value of the magnetic flux is unchanged, but the amount of magnetic flux intersecting with the coil is Change, this is the principle of mutual induction. A transformer is a device that uses electromagnetic mutual induction to transform voltage, current, and impedance.
According to the cooling method:
Dry-type transformer:
This refers to the transformer where the core and windings are not immersed in insulating oil. Cooling methods are divided into natural air cooling (AN) and forced air cooling (AF). Under natural air cooling, the transformer can be operated continuously for a long time under the rated capacity. When forced-air cooling, the output capacity of the transformer can be increased by 50%. It is suitable for intermittent overload operation or emergency accident overload operation; due to the large increase in load loss and impedance voltage during overload, it is in a non-economic operation state, so it should not be placed in continuous overload operation for a long time.
Dry-type transformers have the advantages of strong short-circuit resistance, low maintenance workload, high operating efficiency, small size, and low noise. They rely on air convection for natural cooling or increase fan cooling. They are mostly used for high-rise buildings, high-speed toll stations, electricity, and local lighting. Small capacity transformers such as electronic circuits.
High safety: SG10 transformer has no flammable resin, does not support combustion during use, can be flame retardant, will not explode and release toxic gases, will not cause harm to the environment, other equipment, and human bodies, and is not sensitive to humidity, dust, pollution ; There is no possibility of partial discharge and "cracking" during operation.
High reliability: Both high and low voltage coils use NOMEX insulation materials, and are impregnated with HPI solvent-free impregnated paint by VPI vacuum pressure equipment for many times, and baked and cured at high temperature for many times. The product is class H (180℃), and the main insulation material is class C (220℃), with strong overload capacity and good short circuit resistance. Under good ventilation, a 20% overload operation is allowed.
Energy-saving and environmental protection: after the end of product life, materials such as steel and iron are easy to recycle; all NOMEX paper used will not release toxic substances when burned; other insulating materials can degrade and do not pollute the environment; the loss of the product is low, energy-saving; low noise, design flexible.
According to the following characteristics of dry-type transformers, it is often used in places with high-performance requirements such as fire protection and explosion protection:
1. Safe, fireproof, non-polluting, and can be run directly at the load center;
2. Adopt domestic advanced technology, high mechanical strength, strong short circuit resistance, small partial discharge, good thermal stability, high reliability, and long service life;
3. Low loss, low noise, obvious energy-saving effect and maintenance-free;
4. Good heat dissipation performance, strong overload capacity, can increase capacity operation when forced air cooling;
5. Good moisture resistance, suitable for operation in high humidity and other harsh environments;
6. Dry-type transformers can be equipped with perfect temperature detection and protection systems. Using intelligent signal temperature control system, it can automatically detect and patrol display the working temperature of the three-phase windings, can automatically start and stop the fan, and have an alarm, trip, and other function settings;
7. Small size, lightweight, less floor space, and low installation cost.
1. AN-air (circulation) natural cooling;
2. AF-air cooling. According to the technical requirements of the dry-type transformer, the transformer can meet the rated operation requirements under the cooling condition of AN. But dry-type transformers are usually equipped with fans, which are for emergency use by users. So strictly speaking, there is only one cooling method for dry-type transformers, which is natural air cooling.
Classification of dry-type transformers:
Fully enclosed dry-type transformer: a transformer placed in a pressure-free sealed enclosure and cooled by internal air circulation.
Enclosed dry-type transformer: a transformer placed in a ventilated enclosure and cooled by external air circulation.
Non-enclosed dry-type transformer: a transformer without a protective shell, which is cooled by natural air circulation or forced air circulation.
Oil-immersed transformer:
Rely on oil as a cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, forced oil circulation, etc. Oil-immersed transformer oil has good insulation performance and good thermal conductivity. At the same time, the transformer oil is cheap, which can solve the problem of large-capacity heat dissipation and high-voltage insulation of transformers.
According to usage:
1) Power transformer: used to raise and lower voltage of transmission and distribution system.
2) Instrument transformers: such as voltage transformers, current transformers, measuring instruments, and relay protection devices.
3) Test transformer: It can generate high voltage and conduct high voltage tests on electrical equipment.
4) Special transformers: such as electric furnace transformers, rectifier transformers, regulating transformers, capacitive transformers, phase-shifting transformers, etc.
According to the winding form:
1) Dual winding transformer: used to connect two voltage levels in the power system. (Customized design EI laminated power transformer control transforme)
2) Three-winding transformer: generally used in power system area substations, connecting three voltage levels.
3) Autotransformer: used to connect power systems with different voltages. It can also be used as an ordinary step-up or step-down transformer.
According to the form of iron core: autotransformers are generally used in protective equipment for communication lines, so the calculated capacity is less than the rated capacity, and the size is also relatively small. The corresponding structural materials and effective materials are also reduced a lot. The production cost is greatly reduced, but the transformation efficiency of the autotransformer is very high.
1) Core transformer: used for high-voltage power transformers.
2) Amorphous alloy transformer: Amorphous alloy iron core transformer is a new type of magnetically conductive material, and the no-load current is reduced by about 80%. It is a distribution transformer with an ideal energy-saving effect. It is especially suitable for rural power grids and developing regions. Lower place.
3) Shell transformers: special transformers for large currents, such as electric furnace transformers, welding transformers; or power transformers for electronic instruments, televisions, radios, etc.
According to the number of phases:
Single-phase transformers for single-phase loads and three-phase transformer banks and three-phase transformers for boosting and stepping down in three-phase systems. (Three-phase EI laminated power transformer)
There are mainly oil immersion self-cooling (ONAN), oil immersion air cooling (ONAF), forced oil circulation air cooling (OFAF), forced oil circulation water cooling (OFWF), forced guided oil circulation air cooling (ODAF), forced guided oil circulation water cooling ODWF).
When the strong oil air cooling method is selected, when the oil pump and the fan lose the power supply, the transformer cannot run for a long time. It can't run for a long time even without a load.
Therefore, two independent power supplies should be selected for the cooler. When the strong oil-water cooling method is selected, the oil pump cooling water cannot run when it loses power. The power supply should select two independent power supplies.
The oil-invading self-cooling type has no special cooling equipment. It uses the natural convection effect of oil to bring the heat emitted by the winding and the iron core to the tank wall or the tube (on-chip) radiator and then relies on the convection conduction of air to transfer the heat Distribute. This cooling method is often used in small-capacity transformers.
Oil-invaded air-cooled type is to install a cooling fan on the inside of the disassembled radiator of the transformer and use the fan to blow the air to accelerate the cooling of the oil in the radiator. The same transformer, using air-cooled heat dissipation, can increase the capacity by 30-35%. Medium-capacity transformers generally use air-cooled heat dissipation.
Forced air cooling and strong oil-water cooling are two methods of cooling the hot oil in the transformer oil tank into the oil cooler with an oil pump and then return to the oil tank after cooling to cool the winding and the oil tank. The oil cooler is made into a special shape that is easy to dissipate heat, and the heat in the oil is taken away by using a fan blowing or circulating water as a cooling medium. These two cooling methods have a strong cooling effect. Large-capacity transformers generally use these two cooling methods.
Transformers are subject to large vibrations after long-distance transportation, and body inspection is required. The physical inspection of the transformer is divided into hanging core and hanging cover. Regardless of the hanging core or hanging cover, the contents of the inspection are consistent. Hanging core inspection should be completed within one working day to speed up the inspection process.
Take the hanging core inspection as an example: (1) The hanging core of the transformer should be carried out indoors. If there should be a tent outdoors, it is forbidden to prevent hanging cores in bad weather such as rain, snow, fog, wind, and sand. ⑵The temperature of the hanging core should not be lower than zero in winter, otherwise, the temperature of the transformer will be increased to make the core temperature 10℃ higher than the surrounding temperature. (3) The shorter the core is exposed to the air, the better. The relative humidity should not exceed 16 hours at 65%. When the relative humidity is 25%, it should not exceed 12 hours. The calculation time is from the start of the oil drain to the time of oil filling. ⑷When the weather relative humidity exceeds 75%, the hanging core inspection is not allowed. ⑸ During the inspection of the hanging core, special care should be taken to prevent parts and tools from falling into the tank.
The contents are free from mechanical damage, whether the box cover bolts are intact, the gasket seal is good, the casing surface is free of defects, whether there is oil leakage and oil leakage, whether it is rusted, the paint is intact, whether the accessories are intact, the wheel track and the foundation Whether the rail gauges match.
The voltage transformer is used to convert the electrical output of the power supply to match the voltage of the device, that is, to convert 110 volts to 220/240 volts or 220/240 volts to 110/120 volts. When you want to use 110v 220 volt foreign electrical appliances in the United States, you need to use a step-up transformer. When you want to use 110V equipment in 220V countries/regions, you need a step-down transformer. The transformers that we see every day are generally "bucks", which are commonly found near the community or near the factory. Its role is to reduce the ultra-high voltage to the normal voltage of our residents to meet people's daily power consumption.
Scientekpower inverter manufacturers provide step-up and step-down voltage converter transformers. Both step-up transformers and step-down transformers are reversible and can be used globally at 110v-240v and 50Hz or 60Hz. Also known as power converters, most of our transformers have universal sockets that can accept plugs from various countries. A