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Electrical knowledge

Transformer basics

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Update time : 2018-07-16 10:07:20
Transformer is the use of electromagnetic induction principle, from one circuit to another circuit to transfer power or signal transmission is an electrical energy transfer or as an important component of signal transmission, the main components are the primary coil, the secondary coil and core (core) . In electrical equipment and wireless circuits, commonly used for voltage, matching impedance, safety isolation.
Second, the classification of transformers
In accordance with the species classification is divided into the following four categories:
1, transformer product library: transformers, transformers, reactors, voltage regulators
2, transformer components library: switches, oil conservator, metal expanders, relays, radiators and coolers, pressure relief valve, thermometer, oil level gauge, butterfly valve, hygroscopic, seals, casing, iron core, fuel tank, combination Variable components.
3, transformer raw materials library: silicon steel, wire and cable, non-ferrous metals, insulating materials, transformer oil, dry kerosene gas, paint chemical materials
4, transformer tooling and test equipment library: core processing equipment, coil processing equipment, assembly and processing equipment, fuel tank processing equipment, insulation processing, equipment, dry change manufacturing equipment, test equipment, general equipment
Third, the transformer short-circuit fault analysis
There are many reasons for this. There are many reasons that the short circuit of the transformer leads to internal faults and accidents in the transformer. This is also very complicated, which depends on many factors such as the structural design, the quality of the raw material, the technological level and the operating conditions. However, the selection of the magnet wire is the key. From the recent years, anatomical transformation based on static  of transformer design and selection of the magnet wire, and the actual operation of the electromagnetic force in the larger differences.
1, the way the windings loose, transposed improper handling, too thin, resulting in vacant magnet wire. Damage location from the accident point of view, the more common metamorphosis at the transposition, especially the transposition wire transposition.
2, At present, the calculation program of each manufacturer is based on the idealized model of uniform distribution of the leakage magnetic field, the same diameter of the turns, and the equal phase force. In fact, the leakage magnetic field of the transformer is not uniformly distributed. The iron yoke part is relatively concentrated, and the electromagnetism in this area is also subjected to large mechanical force; the transposition wire generates torque due to the slope climbing changing the force transmission direction at the transposition; due to the factor of elastic modulus of the pad, Pad is not equidistant distribution, alternating alternating magnetic field generated by the alternating force delayed resonance, which is why the core yoke, transposition Department, with the pressure tap the corresponding parts of the first deformation of wire cake root cause.
3, winding pre-tightening force caused by improper control of the general transposed conductor of the wire misplaced each other.
4, anti-short circuit capacity calculation did not consider the temperature of the electromagnetic bending and tensile strength of the impact. According to the test results, the temperature of the magnet wire has a great effect on the yield limit of 0.2, and as the temperature of the magnet wire increases, its bending resistance, tensile strength and elongation All decreased. At 250 , the flexural tensile strength decreased at 50 and the elongation decreased by 40%. The actual operation of the transformer, rated load, the average winding temperature up to 105 , the hottest temperature up to 118 . General transformer operation reclosing process, so if the short-circuit point can not disappear for a moment, it will be in a very short period of time (0.8s) followed by a second short-circuit impact, but due to the first short-circuit current impact, Winding temperature increased sharply, according to the provisions of GBl094, the maximum allowable 250 , then the anti-short circuit winding capacity has dropped significantly, which is why the transformer short-circuit accident after reclosing and more.
5, the use of flexible conductors, is also one of the main reasons for the poor short-circuit resistance of the transformer. Due to lack of understanding of the early or winding equipment and process difficulties, manufacturers are reluctant to use semi-hard wire or design-time requirements in this regard, from the perspective of the faulty transformer is a soft wire.
6, frequent external short-circuit accident, many short-circuit current impact after the accumulation of electrodynamic force caused by electromagnetic softening or internal relative displacement, and ultimately lead to insulation breakdown.
7, Winding turns or wires uncured, anti-short circuit ability is poor. No damage to the early impregnated winding.
Fourth, the routine maintenance of the transformer
1. In order to protect the high-voltage generator and the head mounted insulating oil insulation performance, usually should not be free to open the observation window and loose the screws around to prevent the oil moisture or dust and reduce the insulation performance.
2, check the transformer peripheral lighting, cooling, dust removal equipment is intact, and use a clean cloth to wipe the transformer body and porcelain dust.
3, check the high voltage side of the transformer load switch to ensure flexible operation, good contact, the transmission part for lubrication.
4, opened the high-voltage ground knife, check the ground in the open position is correct, close the high voltage load switch, let the transformer test run, and remove the high-pressure side signage, pay attention to disconnect or close the transformer high voltage load switch, the scene There must be two or more people.
5, When the need to replace the new oil, you should obtain the assistance of the local power sector, check the performance of the new oil, the insulation strength of not less than 25,000 V / 2.5 mm; and the combination of oil within the machine head insulation strength should be 30000 V / 2.5 millimeters or more.
6, with 2500V shake table measuring transformer high and low voltage coil insulation resistance (between the ground and white), confirmed that meet the requirements (at room temperature 30 , 1OKV transformer high voltage side is greater than 20MΩ, low voltage side is greater than 13MΩ. Good grounding wire, after the measurement, should be discharged.
7, high-voltage generator or combination head must have a good grounding wire, ohmmeter should always measure the shell, the console shell, the external ground three are turned on, and tighten the ground bolt.
8, high-voltage generator or combination head must have a good grounding wire, ohmmeter should always measure the shell, the console shell, the external ground three are turned on, and tighten the ground bolt.