1. What is transformer? A: The power transformer is used to change the size of the AC voltage electrical equipment. It is based on the principle of electromagnetic induction, the same frequency, between two or more windings, converting AC voltage and current transmitted power of the stationary electrical equipment.
2. The transformer can be divided into several? A: The use can be divided into: power transformers, and special transformers. Classification of power transformers: (1) divided by the capacity of the transformer: small and medium sized transformers, large transformers, large transformers; (2) according to the number of winding points: two winding transformers, three-winding transformer; (3) Press the high and low voltage coils Have electrical contact points: ordinary transformers, auto-transformers; (4) by way of regulating transformer sub: non-excitation voltage, load voltage regulation; (5) divided by the number of phases: single-phase transformers, three-phase transformer; ( 6) divided by the cooling medium: oil-immersed transformers, dry-type transformers; (7) by a core structure: heart-type transformers, shell-type transformers.
3. Transformer Model and letters mean? A: Model using Pinyin uppercase letters or other suitable to represent the main features of the product, with Arabic numerals denote the level of product performance or design code number and specification code. Example: SGZB 10 - / voltage winding voltage (kV) Rated capacity (kVA) Code foil around the surge level of performance mode (only marked with load) dry air from the cold phases (three phase)
4. What is the significance level of performance code? A: The performance level of the code number the greater the loss, the higher the level. 9 type refers to the load loss is the national standard of 90%, the load loss is the national standard of 90%; 10 type refers load loss is 80% of the national standards, national standards for load loss is 85%.
5. What is the purpose of the transformer is operating in parallel? A: When two or more sets of primary side and the secondary side of the transformer between the terminals of the same polarity, respectively by the same bus link to each other, this operating mode is called parallel operation of the transformer. Objective: (1) to increase capacity; (2) to improve the economy of transformer operation; (3) improve the reliability of power supply.
6. What are the conditions transformer parallel operation should meet? A: The same as (1) a transformer coupling group; change (2) than the same transformer, primary side rated voltages equal pay; short-circuit impedance (3) similar transformer; transformer capacity (4) operating in parallel than is generally not more than 3 :1. Under actual operating conditions, (2), (3) allow for some deviation.
7. What is the rated voltage of the transformer? What is the rated voltage ratio? A: Winding rated voltage (Ur) is in the master tapped tapped winding terminals or between the winding terminals without tap, the induced voltage is specified when the applied voltage or load (for a three-winding, is It refers to the voltage between the line terminals). Transformer rated voltage and power transmission lines connected to conform. Rated voltage is the line voltage, and are an effective value. Rated voltage ratio refers to the rated voltage and another one winding with a lower or equal to the rated voltage of winding rated voltage ratio, so the rated voltage ratio K≥1.
8. What is the nominal frequency transformer? A: The transformer rated frequency is the operating frequency transformer design is based. Our country is 50Hz. That is within the AC alternating cycles per second, represented by the symbol f, the unit name is Hertz. Unit symbol Hz, period and frequency reciprocal relationship, that is T = 1 / f, f = 1 / T. T-- AC alternating each time (or week) is called the cycle time required, the unit name in seconds.
9. What is the rated capacity of the transformer? A: The rated capacity (Sr) is, as the one winding in the specified value of power, and the rated voltage of the winding together to determine the rated current. The main role is the transmission power transformer, its rated capacity and therefore the main data, it is the performance of conventional capacity value, characterizing the size of the transmission power. It is expressed in kVA or MVA. In order to ensure and test it as a basis of the manufacturer's design. When the transformer and the rated voltage is applied, it is determined according to the provisions under the standard conditions of temperature does not exceed the rated current limit.
10. What is the rated current of the transformer? A: The transformer rated current is defined by the transformer rated capacity (Sr) and rated voltage (Ur) derived a current flows through the winding line terminals.
11. What is the transformer load current? A: When the rated frequency of the rated voltage (tapping voltage), is applied to the terminals of a winding, other windings open circuit, the flow through the winding line terminal of the current rms value. Its active component to compensate for the smaller core loss, its larger active component to the field, in order to balance the voltage drop across the magnetic core. No-load current Io is usually expressed as a percentage of the rated current. The larger transformer rated capacity, Io is smaller.
12. What is the load loss of the transformer? A: In a pair of windings, when the line terminal rated current (tapping current) flowing through a winding, and the other winding short circuit at the rated frequency and reference temperature (F-class 120 ℃, H-class 145 ℃) by active power draw, this time, the other winding (if any) should be open. Load losses, also known as short-circuit loss, it is proportional to the square of the load current, coil heat source. In watts, the symbol is represented by W.
13, what is the impedance voltage transformer? A: The two-winding transformer secondary winding short circuit when the voltage of the primary winding flow of the rated current is applied, said impedance voltage. Symbol Uk, usually impedance voltage expressed as a percentage of the rated voltage, namely Uk% = (Uk / Uh) × 100%. Cost and performance impedance voltage transformer size, system stability and power quality related.
14. What is the heating effect of current, how to determine the heat generated by the current in the resistor? A: When a current flows through the resistor, the resistor will heat, electrical energy is converted to heat, a phenomenon called thermal effect of current. Calorie calculation determined by Lenz's Law, namely: resistance through the heat generated by the current and the square of the current, and power-on time is proportional to the resistance. Relation is Q = 0.24I2RT where I-- Current (A) R-- Resistance (Ω) T-- time (S) heat (card) Q-- resistance generated 0.24 equivalent of heat, represents one watt? S heat energy generated 0.24 cards.
15. What is the partial discharge? A: refers to cause partial discharge occurs only between the insulated conductors of a local bridge discharge, namely in the electric field, the insulation system occurs in a discharge part of the region, but did not penetrate the applied voltage between the conductors, which have not yet breakdown This phenomenon is called partial discharges.
16. What is the reason for partial discharge? A: The various parts of the insulator is subjected to non-uniform electric field, and the dielectric is not uniform. Also in the manufacture or use of some residual bubbles or other impurities, so in the insulator surface will appear inside or electric field strength in some region is higher than the average electric field strength, the electric field strength in some regions below the average electric field strength. Therefore, some regions will be the first discharge occurs, while other areas remain insulation properties, which formed a partial discharge.
17, dry-type transformers There are several forms of partial discharge? A: (1) internal winding discharge, that layer dielectric partial discharge between segments; (2) Surface partial discharge; (3) a corona discharge.
18, dry heat transformer winding, which has several forms? A: (1) radiation: infrared radiation that is winding to a lower than ambient temperature spatial propagation of heat; (2) Convection: the heating element is moving through the lower temperature air and heat; (3) Conduction: heat source from directly at high temperature to a lower temperature place.
19, dry type transformer cooling There are several ways? A: The dry type transformer cooling methods are mainly two kinds of self-cooled and air-cooled. AN-- cold air from forced air circulation cooled AF--
20. What is the Connection Symbol winding? A: Connection Symbol windings with a group of letters and a clock ordinal number indicating high, medium (if any) and the low voltage winding coupled manner, and represents medium voltage, low voltage winding of high voltage winding phase displacement relationship generic label. Frequently there are star-connected transformer (three-phase transformer winding end of each phase or three-phase group consisting of three single-phase transformers have the same rated voltage winding end connected to a common point, and the other end connected to the corresponding line terminal .) and delta-connected (three-phase three-phase transformer winding or three-phase group consisting of three single-phase transformers with the same rated voltage windings are connected in series into a closed loop) are represented by the letters of Yyn0, Dyn11, which , Y refers to the high pressure of the star coupler, D refers to the high pressure of delta connection, yn means a low pressure in a star coupler and a neutral point leads, 0,11 the number of constituencies.
21, three-phase transformer connection Y, yn0 and D, yn11 What is the difference? A: (1) when the secondary side of the transformer load asymmetry 2, Dyn11 wiring than Y, yn0 wiring zero shift is small; (zero sequence impedance ratio Yyn0 small) (2) D, yn11 wiring can be improved through the transformer the sensitivity of the current protection devices, simplifying wiring protection; (3) D, yn11 low-voltage mains wiring can improve the sensitivity of the protection device, helping to ensure selective protection levels and expand the radius of the feed; (4) D , yn11 wiring transformer, the secondary neutral current is not restricted. This is a great advantage of D, yn11 wiring, and Y, yn0 wiring secondary neutral currents are not allowed to exceed 25%. (5) The first phase voltage D connection Y connection coil than √3 times higher, and the current small √3 times the diameter thin and therefore more turns.
22, three-phase coupling relationship phase, line voltage and current is what? Answer: (1) Y-shaped link phase current equal to the line current, that Ia = IL; line voltage is equal to √3 times the phase voltage, UL = √3 Ua; (2) D-shaped coupling line current is equal to √3 times the phase current, namely IL = √3 Ia; line voltage is equal to the phase voltage, namely Ua = UL.
23, transformer tap range have? A: Generally tap scope of ± 5%, ± 2 × 2.5%, ± 4 × 1.5%, ± 4 × 2.5% and so on.
24, what role the winding in the transformer? A: The transformer windings inside the circuit device, which is directly connected with the outside of the grid, the transformer is the most important component, often likened to a transformer winding "heart." Change can alter the voltage winding turns, when the winding and core package together, both about the composition of the transformer itself, constitute an electromagnetic induction system, to obtain the desired voltage and current.
25, coil tap for? A: The method of adjusting the voltage transformer is provided on one side thereof a coil tap, in order to increase the removal of part or turns, changing the number of turns, so as to have a method of changing the voltage level adjustment voltage ratio. In the taps, the main points is the ability to work then rated voltage, rated current and rated capacity, other work is the ability to tap the other tap tap winding voltage, current and capacity.
26. Why on high voltage winding pumping tap? A: Because the high voltage windings are usually set in the outermost, leads to tap more convenient, as well as high-side current small, leads to sub escorts line and tap-carrier small part sectional, switch contact portion relatively easy to solve.
27. Why are often multi-coil wires and around? A: After the inner wire through the current, in addition to resistive losses, there are eddy current loss. For resistive losses, with single or multiple coil wires around the system, as long as the same cross-sectional area is the same, but the eddy current loss related to the thickness of the wire, the thickness doubling the eddy current loss increases fourfold if too wide and the lateral leakage magnetic field eddy current loss caused also soared. Therefore, when the current, multi-root and around, the eddy current loss is greatly reduced, so you have to use multiple wires and around. Also when thick wire wound too difficult, but also require the use of multiple wires and around.
28, what is the breakdown of electrically insulating material? Affect the electrical breakdown of the factors? A: When the voltage used in the insulator, they produce a large number of free electrons and ions, due to the acceleration of free electrons or ions generated a lot of kinetic energy, kinetic energy reaches a certain value occurs first free discharge, a phenomenon he called insulation electrical material breakdown. Affect the electrical breakdown of factors: (1) the higher the voltage, the more likely to cause electrical breakdown; (2) voltage is applied to the longer, the more prone to electrical breakdown.
29. What is the thermal insulating material breakdown? Effect of thermal breakdown of the factors? A: Because the increase in the temperature of the insulating material, and dielectric loss is increasing, resulting in a material leakage current, the temperature of the material is more increased. When the insulating material is greater than the increase in the heat of the heat, the aging of the material, resulting in a carbonized material, a phenomenon he called thermal insulating material breakdown. Effect of thermal breakdown of factors: ambient temperature of the material is too high, the heat was poor, insulator too thick, poor thermal conductivity properties, the role of voltage frequency is too high.
30, insulation aging process generated and why? A: The main reason is the heat generated by insulation aging losses arising from the development process for the oxidation, thermal decomposition leading to reduced mechanical strength, drawing resistance enhancement. Reasons: (1) electrical aging. Electrical aging can be divided into partial discharge aging, causes the air gap, crack, peel, bubbles, etc., the development process of oxidation, perforated wire, insulation thickness reduction, insulation breakdown; electrical aging Another reason is that resin discharge, as charged body raised and insulation mixed with foreign matter. (2) stress aging. The main reason is heat stress, heat around the role of vibration stress, the development process is cracking, peeling or other generation gap, develop into electrical aging. (3) environmental aging. The main reason is to run the site moisture, dust and harmful gases, the development of fouling, moisture absorption produced creepage, lower insulation level.
31. What is the life of the insulating material 6 degrees given the meaning? A: The economic life of the transformer insulation material is generally defined as 20 years, the relationship between the transformer insulation life (in years) and long-term operating temperature can be expressed, namely: A = 20 × 298/6 × 2-t / 6 Where t- insulation operating temperature, (℃) does not exceed 140 ℃. The temperature is increased or decreased 6 ℃, insulation aging and life expectancy reduced by half or double, this law is set to 6 degrees.
32. What cold-rolled silicon steel chemical composition and its performance? A: The chemical composition of cold-rolled silicon steel sheet approximately 3% to 5% silicon, 0.06% carbon, 0.15% manganese, 0.03% phosphorus, 0.25% sulfur and 5.1 to 8.5% aluminum, the remainder being iron. Role of these elements in the silicon steel sheet is: (1) Carbon (C) increases the hysteresis loss of the steel sheet. (2) Silicon (Si) can weaken the adverse effect of carbon, i.e., to reduce the hysteresis loss, but also improve the magnetic permeability and resistivity and prolong long-term use of the magnetic effect brought about by the aging deterioration. (3) sulfur (S) will produce heat brittle silicon, increased hysteresis loss and reduce the magnetic flux density. (4) manganese (Mn) can induce a phase change generated in the steel, decarburization and desulfurization were unfavorable, resulting in decrease of magnetic induction. Impurity elements present in steel are non-magnetic or weakly magnetic substances, their presence, causing lattice contorted, dislocation, vacancy and internal stress, thus the magnetization difficult.
33, the type of silicon are those? A: (1) can be divided into four categories according to silicon: low silicon (silicon 0.8 to 1.8%), the silicon (silicon 1.8 to 2.8%), higher silicon (silicon containing 2.8 to 3.8%) and high silicon steel (3.8 to 4.8% silicon). (2) according to the rolling method can be divided into hot-rolled and cold-rolled silicon steel sheet. (3) can be divided by a grain-oriented silicon steel sheet and non-directional electromagnetic solenoid oriented silicon steel sheet.
34, how to judge the performance of silicon? A: It depends on the good performance silicon different magnetic field density of magnetic induction value and unit iron loss. Under the same magnetic field strength (i.e., ampere turns per unit length), the higher the magnetic induction, silicon steel sheet, the better the performance, at the same frequency, the same unit of iron loss value (W / kg) smaller when the magnetic flux density, the silicon steel sheet the better the performance.
35, in the transformer, the primary insulation, vertical insulation which each finger? A: The winding insulation of their own other than the part of the main insulation, including the tank insulation, and insulation plate to clip the core insulation on the other winding phase of the same, as well as insulation for the different phase windings, the end Insulation is also within the scope of the main insulation. Winding insulation itself is a longitudinal insulation, including inter-turn insulation, insulation insulation between segments and segments with electrical insulation between the plates between layers.
36. What are the characteristics load tap? A: The transformer voltage mode is usually divided into non-excitation regulator and load voltage regulation. When the secondary without load, voltage disconnect from the grid when the non-excitation voltage, load tap tap fitted with load decomposition, in the case of a transformer with a load, by operating the mechanism can transform tap tap position switch after the voltage controller can be equipped with automatic voltage regulator also realize that the transformer output voltage within a range.
37, oil-immersed in transformer oil do? A: (1) insulation. Transformer oil as an insulating substance, so that between the winding and the winding, an interlayer, and a good insulation between the windings and ground core and the fuel tank, thereby increasing the dielectric strength of the device, (2) cooling effect. Transformer oil has a larger heat capacity, at the same time, the oil-filled equipment with good heat circulation circuit, and so be able to run in the transformer core and windings comes out of the heat, transfer to a cooling device, play an effective cooling effect. (3) the role of extinction. In OLTC transformers, insulating oil contained within the switch, there is the role of extinction.
38, oil-immersed transformers, sealed transformers What are the characteristics? A: sealed transformer isolated way since the oil in contact with air, the insulation will not damp and aging rate is greatly reduced, thus improving reliability and service life of the transformer. Before running without hanging core examination, so users will save money. Core, coil, and the body of this transformer has advantages as well as process and structure are different: (1) the body of the vacuum oiling, the elimination of the insulating material moisture and air, to ensure long-term operation of transformer life. (2) fuel tank using corrugated expansion tank or radiator shrink, cancel conservator. Changes in the volume of oil from the tank to adjust the elastic compensation.
39. What do the test transformers is the purpose? A: The purpose of the transformer transformer performance test is to verify compliance with the relevant standards and technical conditions, it was found the existence of a variety of defects affecting the operation of manufacturing, in addition, through the analysis of test data to find out the improved design, process improvement way.
40. What are the characteristics of foil windings? A: The foil winding biggest characteristic: in a dedicated reel machine rolling, high degree of automation, providing higher productivity and product quality. That layer between interturn longitudinal capacitance is large, eliminating the helix angle, short-circuit capacity is relatively strong impact, high mechanical strength, easy construction, the axial and radial error is small, easy to guarantee geometry, turn to turn more closely, there is not easy bubbles, smooth surface.
41. What are the structural characteristics of the arc suppression coil is? A: It is in the structure of a single-phase core reactors, which in addition to the primary coil, there is a fixed meter record Petersen coil winding operation purposes, the meter will be set for the coil rated voltage 100V, rated current 10A.
42. What is the role Petersen coil in the power grid? A: in the circuit, flowing through ground capacitance will produce intermittent arc, in the role of intermittent arc, in the power system overvoltage, could endanger the insulation weak link, causing the accident to expand, in order to make it to intermittently arc quickly extinguished, it must be ground current through the inductor current to compensate for capacitive current. Petersen coil is used in a reactor for this purpose. Transformers process knowledge
43, transformer coil in the form of what kinds? A: The single cylinder type cylinder type, double cylinder type multi-layered cylindrical coil and foil generally cylindrical segmented foil, foil coil segment continuous generally continuous, semi-continuous tangle tangled continuous type, ordinary type tangled tangled floral style pancake coil within the shielded spiral single screw, twin screw staggered four-spiral
44, what is winding around to? A: The winding wire wound around the direction is referred to. Ask around about to be divided into left and right about the two kinds. Winding around due to the different directions in which the current and the resulting magnetic field direction and when the magnetic field changes direction electromotive force induced in the windings are different. Winding around the winding head to be determined by a start. Wound windings, refers to the left around the operator from the right to the left wound. It refers to the right around the operator from the left to the right side wound. So there is a simplified formulas, "right from left around to; left and right around to."
45. The use of high voltage winding continuous What are the benefits? A: Continuous end supports large, short circuit axial force changes little, very stable. At the same time, good heat dissipation. Therefore, SG10 product continuous use of high voltage winding.
46, in the winding, a plurality of parallel wires need to be transposed, transposition what purpose? Answer: by transposition (1) the parallel of each wire in the location of the leakage magnetic field are the same (2) equal to the length of the wire after transposition.
47, in a double helical winding, what is a uniform transposition? A: The first uniform crossover transposition is evenly distributed on the winding, for the double helix parallel bits equal to the number of wires, each transposition at the top of the cake A line to another line of a wire cake top B while above the bottom line of a wire cake B moves to line A of cake, all transposition by sequentially changing the line wire cake cake to another line, and come back to the original line position cake.
48, in the winding, the solder joint requirements? A: (1) the thickness of less than 1.7mm flat copper using lap welding, take the first part of file into wedge, silver brazed welding; (. 15% silver electrodes using silver-copper electrode, increase its resistivity) greater than 1.7 mm using butt. (2) close to a solid weld joints sanding to frustration level; (3) can not be transposed at the horn, nor between the comb; (4) a plurality of wires welded should be staggered, staggered over a distance of 80mm ; (5) from the head and the horn must tap 2 stay outside; (6) and around each of the plurality of solder can not more than one, the number can not exceed the welding winding and the number of wire wound 1 / 2,6 the number above and around the roots, the welding can not exceed 1/3 of the number of the number, but also to stagger joints; (7) does not allow copper scrap fell winding.
49, in a continuous winding, stays placement What are the requirements? A: If you stay away from unequal, coil winding can not be a round to make the main insulation from the big and small, the ability to withstand voltage strong or weak, weakness may breakdown or partial discharge exceeded. So stay evenly distributed on the circumference, the distance between the error stays not exceeding 3mm, with a strut up and down the vertical shall not exceed 2mm.
50, layer type coil layer should rise attention to what the problem? A: The lead position adjacent layers staggered liters a grid, so as not to increase the size of the department of radiation, low pressure layer type coil liter package to add insulation layer. When placing an insulating layer, insulating paper width should be higher than the winding (including end insulation) is slightly smaller than the total height of 2 ~ 4mm, layer insulation should be staggered, end staggered, each insulating paper take the head of not less than 20mm.
51, high-voltage continuous winding, the first and last two cake wrapping paper required to achieve what purpose and what are the requirements? A: The first and last two cake wrapping paper is to strengthen the insulation, prevent breakdown. When the package of paper, to force tightening turns, then both sides of sheets of paper with 0.08mmNOMEX half Diego Pack 2 layer, the force should be appropriate to maintain the end face flat and smooth.
52, winding faults which may arise? A: (1) When the transformer winding suffered severe external short circuit, a line winding one or more turns will be dislocation occurs, which may cause a short circuit between turns, and can not run. (2) If the quality of the transformer coil terminals is not good, then when the transformer load, whereby the winding may overheat, causing insulation charring, resulting in inter-turn (interlayer between segments) short circuit; (3) construction which, layer interturn mixed metals, water, impurities, etc., will cause partial discharge, as well as insulation breakdown; (4) long running overload, insulation aging or even lead to breakdown; (5) between the parallel conductors shorted shares, produce circulation and overheating. (6) the airway is blocked, resulting in the winding runtime can not generate heat comes out.
53. What is the impact on the quality of the wire transformer? A: The surface of the wire sharp corners, burrs, impurities and other defects clip, if not carefully removed, wrapped in turn insulation paper, will turn insulation displacement, which is equal to the local thinning turn insulation, when the transformer do induction voltage test , turn insulation puncture more serious, there will be the insulation breakdown.
54, in the package of paper, overlapping package paper pay attention to what? A: The overlap wrapping paper, wrapping paper lap width should be no less than 2mm, no more than 3mm, the control packet paper thickness, number of layers of paper when the package is more, the intermediate layer allows a small amount of paper to take the first lap or less than 2mm, but inside and outside layer must ensure overlapping dimensions. Two adjacent Wraps take the head staggered distance of 1/4 to 3/4 tape width.
55. What is the purpose of winding press-fit? A: In order to ensure the winding can withstand axial force to live a short circuit, but also to ensure that the requirements of the axial dimension, so to add a greater pressure on the axial direction of the coil.
56. What is the purpose of winding dry? A: Because the windings are made of wire and insulation material, under normal circumstances, the insulating material containing 6% to 8% of water in the manufacturing process of winding, with the climate change absorbs moisture in the air, reaching equilibrium. The water will affect the electrical strength of the insulating material while the insulating material after wet, the thickness should be expanded, affecting the axial dimension of the winding. In order to increase the insulation performance and meet the material dimension of contraction and stability, good wound winding must be dried.
57, how to improve the quality of winding drying? A: In order to improve the quality of the winding drying, there are two factors that must be carefully considered: (1) control the drying temperature; (2) increasing the degree of vacuum equipment.
58, when the winding press-fit, why is there pressure to meet the requirements and winding axial height high? A: Mainly because there is no strict accordance with the process execution, the low temperature drying winding preheating and drying time to end, not in strict accordance with the requirements of the vacuum, and after drying the winding is placed in the air a long time, the winding insulation pieces absorb moisture again.
59, winding vacuum pressure impregnation what purpose? A: For the purpose of winding impregnation process are: (1) to enhance the mechanical strength of the winding; (2) to enhance inter-winding layers, dielectric strength between turns; (3) to reach three anti- (moisture, salt spray, mildew ) requirements.
60, the winding surface is not smooth, there is a tumor paint, paint scar is what causes? A: drip paint enough time, before drying not scrape with a scraper tumor accumulation of paint, this is because the varnish solid content less, and use a long time, insulating paint paint coagulate into gel blocks, which paint blocks stick to the surface or between the winding segment, and therefore winding surface is not smooth, the presence of tumor paint, paint scar.
61, the coil insulating resin layer cracking What are the reasons? A: (1) high temperature curing temperature is too high or too long; (2) coils inside presence of local stress concentration points; (3) plastic yarn imbalance, too much glue; Fail (4) the quality of plastic, rubber expansion coefficient and copper conductor difference is too large; (5) stripping difficulties, excessive beating resulting resin insulating layer internal damage.
62, epoxy resin and hardener mixed What are the requirements? A: (1) an epoxy resin and hardener should be mixed in a plastic canister vacuum mixing and degassing evacuated; (2) to be uniformly stirred; (3) the ratio in proportion to the specification requirements; (4) to prevent dirt and Water injection; (5) the use of glue mixture valid, the instructions provided by the manufacturer, usually not more than eight hours.
63, what role the core in the transformer? A: magnetic circuit portion of the transformer core is made of a high permeability electrical steel sheet. Transformer winding through a very small excitation current in the core have a great flux induced in the other winding potential need. In other words, in a winding pass to alternating current, when the second winding connected to the load, this will also flow through the windings of an AC current. According I1U1 = I2U2 conversion relation, by the power transfer power to the load, which is the main role in the transformer core. Another role is to do the transformer skeleton, internal transformer All parts, including windings, switches, supports, clamps and other support and fixation.
64, the core loss from which parts? What impact is mainly due to their size? A: The core loss by the hysteresis loss, eddy current loss, additional loss core components. Influence is mainly due to its size: hysteresis loss: mainly determined by the silicon material, bent and beat in the processing, also affected. Eddy current loss: burr big, bad insulation between the sheets, silicon steel sheet is too thick. Core additional loss: structured products, (such as straight, miter joints), silicon quality conditions in the process of.
65 core brands What is the significance? A: For example: 30 Q 130 represents a unit of iron loss, the number is 100 times the iron loss values indicate the orientation of cold-rolled steel represents the nominal thickness, the number is 100 times the nominal thickness
66, steel slitting shaped storage should pay attention to? A: To store the label, clean, cut at the cut end of each film roll topcoat rust oil to prevent rust section volume increase caused by the core loss.
67, core Why is two or thirteen a Diego? A: When a piece of a stack of work too, but a few pieces of each stacked more than three films, loss and no-load current increases, and the seams sheet friction becomes smaller, so large and medium core laminated films are generally is two or three batches.
68, in the laminations auxiliary clamps and clamps if not in a horizontal plane, what will the consequences appear? A: The core columns droop, resulting in leg skew. Therefore, the auxiliary clamps and clamps must face the same level.
69, the core of the insulation resistance to reach the number? A: The core insulation resistance ≥100MΩ.
70, after the completion of the core stacked, technical checks should achieve what eligibility criteria? A: The standards are to be met: (1) clamped lashing core to securing reliable; (2) ground blade is inserted at the 2-3 level, do not loose, grounding reliable insertion depth ≥80mm, ground lug jumper core Department allowed to short circuit; (3) Epoxy curing banding tape should not be loose, should be smooth, clean, thickness difference ± 0.2mm, a pitch difference of ± 10mm; (4) core column inclination of not more than 5mm; (5 ) Total thickness difference of ± 1mm, the diameter difference of + 2mm, from the seam uneven ≤0.5mm; (6) clamps to the core, qualified through one minute withstand voltage 2500V shake table.
71, core Why grounded? A: The core and the metal structure in the alternating electric field of the coil, due to the different location, the induced electromotive force is also different. Although the potential difference between them is small, but also by a small distance and discharge insulation. In order to prevent the discharge, the core and the metal structure must be grounded.
72, the core must be grounded Why? A: Because the core multi-point grounding in the future, will result in a short circuit around the core operating flux turns exist, causing the accident, the excess is not formed at the same time short to ground turns, will increase circulation and core losses in the cross section, can also cause accidents. So the core must be grounded.
73, what is the reason of the operation of the transformer noise is? A: (1) is energized after silicon, silicon molecular magnetic domains to form sound repetitive stretching; (2) the seams magnecular telescopic sound occurred; (3) the role of electric power in the coil, clamps, bolts etc. vibration occurs. The above is a normal sound, but if the core in the assembly manufacturing process, nipped not tight cause loose laminations and core joints large, when there is a bad piece and flaps and other problems can occur so that the core has a shrill noise.
74, SG10 products have any technological measures ensure low noise? A: (1) selection of high-quality imported high permeability cold rolled grain oriented silicon steel sheet; (2) the use of the yoke cores without punching, stem glass adhesive tape lashing drawing board structure; (3) coil and structure buffer between the silica gel plates, silencers; (4) the core as a whole surface is coated with a special epoxy rust, rust-proof and shock-absorbing both; (5) NOMEX paper itself has a certain sound-absorbing function.
75, the insulating member is damaged and cleanliness have any effect on the electrical performance? A: The insulating member generally refers to solid insulating parts, in order to ensure its electrical strength, in addition to material of the insulating member itself related, between live body must also ensure that there is a certain degree of insulation from damage to the insulation member is reduced to climb from, or between electrified bodies resulting inter discharged. Clean insulating member or not a great impact on the electrical strength, if there is dust on the insulating member, there are many metal dust particles, clusters are arranged in the electric field is formed between the charged body passage (bypass), thus undermining the insulation strength, resulting in a discharge, the higher the voltage, the more serious dust free, the easier discharge.
76, the front coil suit to pay attention to what? A: The first coil suit must: (1) be familiar pattern, a clear technical requirements; (2) Check the coil a. Card process is complete, test, signature; b. Check the same coils A, B, C-side DC resistance label is correct; c. Check the coil head and tap outlet location to meet the requirements; d. Check axial height are the same; e. And a plurality of winding short circuit Check with megger.
77, the assembly process, the welding should pay attention to what? A: (1) do the protection work before welding near the insulation with asbestos rope flooding will qualify wrapped ensure qualifying insulation does not burn; (2) Carbon Block file flat surface before welding to braze the clip on