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Transformer elementary knowledge

Views:8     Author:Site Editor     Publish Time: 2017-10-25      Origin:Site


1.What is a transformer?

Answer: The power transformer is uses for to change the alternating voltage size the electrical equipment. It is acts according to the electromagnetic induction the principle, by the same frequency, between two or more windings, the transformation alternating voltage and the electric current transmits the electrical energy static electrical equipment.

2.Which how many kinds can the transformer divide into?

Answer: May divide into according to the use: Power transformer, special transformer.

  Power transformer's classification:

(1)Accommodates weighing out according to the transformer: Middle and small scale transformer, large-scale transformer, extra large type transformer;

(2)According to winding number weighing out: Double winding transformer, three winding transformer;

(3)Has the radio relation minute according to the high and low pressure coil: Ordinary transformer, from pair transformer;

(4)Presses the mode minute according to transformer's accent: Presses without the excitation accent, has carries adjusts the pressure;

(5)According to several points: Single phase transformer, three-phase transformer;

(6)According to cooling medium minute: Oil bath type transformer, dry transformer;

(7)According to core construction minute: Heart type transformer, shell type transformer.

3.What meaning the transformer product model and do the letter represent?

Answer: The product model uses the Pinyin capital letter or other appropriate letters represented that the product chief feature, represents the product performance horizontal symbol or the design serial number and the specification symbol with the Arabic numeral. Example:

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4.What significance does the performance capability symbol have?

Answer: A performance capability generation of serial number is bigger, loses is smaller, the level is higher.9Is refers to the no-load loss is the national standards90%, the load loss is the national standards90%10Is refers to the no-load loss is the national standards80%, the load loss is the national standards85%

5.The transformer parallel operation's target is anything

Answer: Two or many transformer's sides as well as between two side like polarity post, through the identical bus bar distinction interconnection, this run mode is called transformer's parallel operation.

Target: (1) adds the capacity;

(2) enhances the transformer run the efficiency;

(3) enhances the power supply reliability.

6.What condition should the transformer parallel operation satisfy?

Answer: (1) transformer's joint category is the same;

(2) transformer's changing compared to same, pays the rated voltage distinction to be equal side originally;

(3) transformer's short-circuit impedance is close;

(4) parallel operation's transformer capacity is not generally more suitable than surpasses3:1

Under actual operating condition, (2), (3) permits some deviations.

7.What is transformer's rated voltage? What calls the fixed ratio-voltage?

Answer: Winding's rated voltage (Ur) is in is in the belt minute which the main minute meets to meet winding's post once in a while not to bring the winding post which the minute meets, designates when voltage or idling which exerts induces the voltage (regarding three windings, is refers to line post voltage). Transformer's rated voltage with the power transformer line which links tallies. The rated voltage refers to the line voltage, and by effective value representation.

   The fixed ratio-voltage is refers to a winding's rated voltage to have low or the equal rated voltage winding's ratio of rated voltage with another, therefore fixed ratio-voltageK>=1

8.What is transformer's nominal frequency?

Answer: The transformer nominal frequency is the run frequency which the transformer design rests on. Our country is50Hz. Namely in each second alternating current alternation periodicity, with symbolfRepresentation, its unit name for hertz. Unit codeHz, the cycle and the frequency are the reciprocal relations mutually, namelyT=1/ff=1/T

T- - an alternating current each alternation time (or one week) needs the time calls the cycle, the unit name for the second.

9.What is called transformer's rated capacity?

Answer: Rated capacity (Sr) is some winding's apparent power designated value, resolves its nominal current together with this winding's rated voltage. Transformer's leading role transmits the electrical energy, therefore the rated capacity is its main data, it is displays the capacity the habitually used value, the attribute transmission electrical energy size. It useskVAOrMVARepresentation. Takes the factory design by it the guarantee and the experimental foundation. And exerts time the rated voltage to the transformer, according to it determined that does not surpass the temperature rise limiting value under the standard rated conditions the nominal current.

10.What is transformer's nominal current?

Answer: Transformer's nominal current is refers by transformer's rated capacity (Sr) and rated voltage (Ur) infers flows through the winding line post the electric current.

11.What is transformer's zero-load current?

Answer: When under nominal frequency's rated voltage (minute meets voltage), exerts to a winding's post, when other windings lead the way, flows through this winding line post the electric current root-mean-square value. It small active component uses to compensate iron core's loss, it great active component with by the excitation, by is balanced the iron core magnetism pressure drop. Zero-load currentIoUsually by nominal current percentage representation. The transformer rated capacity is bigger,IoIs smaller.

12.What is transformer's load loss?

Answer: In a pair of winding, when the nominal current (minute meets electric current) to flow through a winding's line post, and another winding short-circuits time, under nominal frequency and reference temperature (FLevel120℃,HLevel145℃) absorbs active power, this time, other windings (, if has) should lead the way. The load loss also calls the short circuit to lose, it is proportional with load current's square, is heat source which the coil has a fever. The unit is the tile, the symbol usesWRepresentation.

13AnythingYesTransformer's bucking voltage?

Answer: When the double winding transformer two windings short-circuit, winding circulation nominal current exerts electricity add in for tare etc bucking voltage. The symbol isUk, the bucking voltage indicated usually by rated voltage's percentage, namelyUk%=(Uk/Uh) *100%. The bucking voltage size and transformer's cost and the performance, the system stability and the power supply quality concern.

14th,AnythingYesDid the electric current thermal reaction, how determine that electric current quantity of heat which produces in the resistance?

Answer: When the electric current has flowed the resistance, the resistance will have a fever, will convert the electrical energy into the heat energy, this kind of phenomenon named electric current thermal reaction.

The thermal determination calculates with the lenz law, namely: Resistance after the electric current produces thermal and the electric current square, the resistance and the circular telegram time are proportional.

  The relationship isQ=0.24I2RT

In the formulaI- - electric current (A)

R- - resistance (OMEGA)

T- - time (S)

Q- - the resistance produces quantity of heat (card)

0.24Mechanical equivalent of heat, representation1WattA second electrical energy produces the quantity of heat is0.24Card.

15What is the shelf depreciation?

Answer: The shelf depreciation is directs between the conductor the insulation to have the local bridge joint's one kind of electric discharge only, namely under the electric field function, in the insulated system has a part of area to have the electric discharge, but does not have the penetration to exert the voltage between the conductor, namely not yet penetrates, this kind of phenomenon calls it the shelf depreciation.

16The shelf depreciation produces what is the reason?

Answer: The insulator various spots withstanding electric field is non-uniform, moreover the dielectric medium is also non-uniform. Will remain in the manufacture either the use process some air bubbles or other impurities and so on, will therefore present certain areas in the insulator interior or the surface the electric-field intensity to be higher than the average electric-field intensity, certain area's electric-field intensity will be lower than the average electric-field intensity. Therefore, certain areas first will have the electric discharge, but other areas still held the insulation the identity, this has formed the shelf depreciation.

17How many forms does the dry transformer shelf depreciation have?

Answer: (1) winding interior electric discharge, namely level, section isolation medium shelf depreciation;

(2) superficial shelf depreciation;

(3) corona discharge.

18Which how many forms does the dry type transformer winding radiation have?

Answer: (1) radiates: Namely outside winding infrared emission wave direction ambient temperature low space propagation quantity of heat;

  (2) transfers: Is the heating element is radiating through the temperature low movement air;

  (3) conducts: Is the heat source compares the high place from the temperature to compare the low spot directly to the temperature.

19How many kinds do the dry transformer coolant conditions have?

Answer: The dry transformer coolant conditions mainly have the self-cooling and the forced-air cooling two kinds.

AN- - air self-cooling

AF- - air forced circulation forced-air cooling

20What is winding's joint group label?

Answer: Winding's joint group label is instructs the high pressure with group of letters and the clock ordinal number, to press (, if has) and low-voltage winding's joint mode, and represents the pressure, the low-voltage winding to the high-voltage winding phase displacement relations general label.

The transformer has the star type to join (a three-phase transformer each phase winding end or composition three-phase group's single phase transformer's three common has a same rated voltage winding's end connection to a common point, but another end connection to corresponding line post. ) and the triangle junction (three-phase transformer's three phase windings or composition three-phase group's single phase transformer's three have a same rated voltage winding mutually series connection closed path,) respectively uses the letter representation isYyn0Dyn11, among,YRefers to the high pressure is the star type joint,DRefers to the high pressure is the triangle junction,ynRefers to the minimum pressure and has the neutral point for the star type joint to draw out,011For category number.

21, three-phase transformer wiringWhat Y, yn0 and do D, yn11 have to distinguish?

Answer: (1) when transformer two side load not symmetry2Dyn11Wiring ratioYyn0The wiring zero drift is small;(Compared toYyn0Zero foreword impedance is small)

(2) usesDyn11The wiring mode may enhance the transformer electric current relay protection installment the sensitivity, the simplified safeguarding wiring;

(3) usesDyn11The wiring mode may enhance the minimum pressure skeleton line protective device the sensitivity, is advantageous in the guarantee all levels of protective device selectivity and the expanded feed radius;

(4)Dyn11The wiring transformer, its two zero curve electric current does not make the limit. This isDyn11A wiring enormous merit, butYyn0The wiring two zero curve electric currents do not permit to surpass25%

(5)DConnection ratioYConnection coil phase voltage Gao √3Time, but electric current small √3Time, therefore the line diameter is thin, but the number of windings are many.

22The three-phase joint, the line voltage, the electric current relations are what kind of?

Answer: (1)YThe shape joint interphase current is equal to the line electric current, namelyIa=IL; The line voltage was equal to3Time of phase voltage, namelyUL=3 Ua

  (2)DThe shape ties the electric current to be equal to √3Time of interphase current, namelyIL=3 Ia; The line voltage is equal to the phase voltage, namelyUa=UL

23, which does transformer's minute meet the scope to have?

Answer: Generally the minute meets the scope to have±5%, ±2*2.5%, ±4*1.5%, ±4*2.5%And so on.

24, what does the winding affect in the transformer?

Answer: The transformer winding frames device's internal circuit, it and the outside electrical network direct connected, is in the transformer the most important part, often makes the winding ratio the transformer“heart”. The winding number of windings' change may change the voltage, when winding and iron core coverall when together, both circles composes the transformer itself, and the framing induction system, may obtain the voltage and the electric current which needs.

25What does the coil tapping have to affect?

Answer: The transformer regulation voltage's method is sets the minute in its one side coil to meet, excises or adds a part to turn, change number of windings, thus achieves the change ratio-voltage the having steps regulation voltage method. Meets in the tap in the minute, the host divides the working ability which meets is the rated voltage, the nominal current and the rated capacity, other divide the working ability which meets are other divide meet circle the component to meet the voltage, the electric current and the capacity.

26Why takes a percentage on the high-voltage winding the attachment?

Answer: Because the high-voltage winding passes the stereotype in most outside, draws out the tapping to be quite convenient, but also has the high-tension side electric current to be small, draws out divides meets the lead wire and the tap switch carries the stream partial sections to be small, the switch contact part is quite easy to solve.

27Why does the coil use many wires frequently and circles?

Answer: In wire after the electric current, besides ohmic loss, but also has the eddy current loss. Regarding the ohmic loss, the coil leads the wire system with the simple root or many, so long as the cross-sectional area same is the same, but eddy current loss and conductor thickness related, thickness doubles, eddy current loss quadruple, if the too wide transverse stray field causes the eddy current loss also increases suddenly. Therefore the electric current is big time, uses many and circles, the eddy current loss to reduce greatly, therefore uses many wires and circles. Moreover the wire is too thick when circles the system to be also difficult, also needs to use many wires and to circle.

28, anythingYesInsulation material electric breakdown? Which does the influence electric breakdown's factor have?

Answer: When the voltage uses on the insulator, then has produced the massive free electrons and the ion, because the free electron or the ion accelerated motion has had the massive kinetic energy, the kinetic energy achieves when certain value first has had the dissociation electric discharge, this kind of phenomenon is called the insulation material the electric breakdown.

The influence electric breakdown's factor includes:

(1)The voltage is higher, easier to create the electric breakdown;

(2)The voltage response time is longer, easier to have the electric breakdown.

29, anythingYesInsulation material thermal breakdown? Which does the influence thermal breakdown's factor have?

Answer: Because insulation material temperature's adding, the dielectric loss increases unceasingly, has produced the material leakage current, makes the material the temperature more to advance. When the insulation material adds when the quantity of heat is bigger than the dissemination the quantity of heat, then causes the material to get older, thus has created the material carbonization, this kind of phenomenon is called the insulation material the thermal breakdown.

The influence thermal breakdown's factor includes: Around the material hyperpyrexia, radiates the condition not to be good, the insulator is excessively thick, the material heat conduction performance is not good, the function voltage frequency is excessively high.

30, the insulation aging produces process and reason?

Answer: The insulation gets older the primary cause is the heat which produces by the loss, the developing process is the oxidation, the thermal decomposition causes the mechanical strength to reduce, absorption enhancement and so on.

Reason:

(1) electricity aging. The electricity gets older may divide into the shelf depreciation to get older, has the reason for the air gap, the chap, the peeling, the air bubble and so on, the developing process for the oxidation, the perforation wire, insulation thickness reduces, puncture of insulation; The electricity gets older another reason is the resin electric discharge, because in the charged body bulge and the insulation mixes has the foreign matter.

(2) stress aging. The primary cause is a thermal load, the hot surroundings affect, the vibratory stress, the developing process for the chap, the peeling and so on produces the air gap, develops the electricity aging.

(3) conditions aging. The primary cause is the run scene humidity, the dust as well as the noxious gas and so on, the developing process is the damage, the absorption of moisture produces crawls the electricity, lowers the insulation level.

31, in insulation material service life6What is the formulary meaning?

Answer: The transformer insulation material's economy service life general determination is20The year, the transformer insulation's service life (unit for year) and the long-term operating temperature's relational available equation below indicated that namely:

A=20*298/6*2- t/6

In the formulat- the insulation operating temperature, (℃) does not surpass140℃.

The temperature elevates every time or reduces6℃, the insulation aging life reduces one half or enhances one time, this kind of rule is6Formulary.

32, what the cold rolling silicon steel plate's chemical composition and are the performance?

Answer: The cold rolling silicon steel plate's chemical composition is approximately3%~5%Silicon,0.06%Carbon,0.15%Manganese,0.03%Phosphorus,0.25%Sulfur sum5.1~8.5%The aluminum, other are the iron. These element's in silicon steel plate function is:

(1)Carbon (C) will increase steel plate's hysteresis loss.

(2)Silicon (Si) may weaken the carbon the ill-effect, the ageing action which namely the reduction hysteresis loss, simultaneously may enhance the magnetic conductivity and the electronic resistivity, which the extension long-term use brings magnetism goes bad.

(3)Sulfur (S) will cause the silicon steel plate to have hot shortness, will add the hysteresis loss, will reduce the magnetic induction intensity.

(4)Manganese (Mn) can urge in the steel to produce changes, causes the decarbonization and the desulphurization carries on disadvantageously, thus causes the magnetic induction reduction.

In the steel exists the impurity element is the non-magnetism or the weak magnetic substance, their existence, creates the crystal lattice crooked, the dislocation, the vacancy and the internal stress, thus magnetization difficulty.

33, silicon steel plate's type has these?

Answer: (1) may divide into four categories according to the silicon steel plate: Low silcon steel (including silicon0.8~1.8%), silcon steel (including silicon1.8~2.8%), high silcon steel (including silicon2.8~3.8%) and high silcon steel (including silicon      3.8~4.8%).

(2) may divide into the hot rolling silicon steel plate and the cold rolling silicon steel plate according to the rolling method.

(3) may divide into the directional electromagnetism silicon steel plate and the astatic electromagnetism silicon steel plate according to the grain orientation.

34How to judge silicon steel plate's performance?

Answer: The silicon steel plate performance good is decided by in its different magnetic induction magnetic induction value and the unit iron loss. Under the identical magnetic field strength (i.e. unit length's number of ampere turns), the magnetic induction is higher, silicon steel plate's performance is better, under similar frequency, similarly time magnetic-flux density unit iron loss value (tile/The kilogram) is smaller, the silicon steel plate performance is better.

35In the transformer, advocates the insulation, which vertical insulation each figure of?

Answer: The winding to itself outside other parts of insulations is the main insulation, including to fuel tank's insulation, clamps and clamp's insulation to the iron core, to the identical other winding's insulation, as well as to the different phase winding's insulation, carries the insulation also to belong to the main insulation category. Winding's insulation is the vertical insulation, including turn-to-turn insulation, layer insulation, section insulation as well as line segment with electroplation between insulation.

36Has carries adjusts the pressure to have any characteristic

Answer: The transformer accent presses the mode is usually divides into without the excitation accent presses and has carries adjusts the pressure. When two times do not have the load, one time separates when with the electrical network the accent pressure is adjusts the pressure without the excitation, has carries the regulating transformer fittings to have carries the resolution to meet the switch, in the transformer belt load's situation, may transform tap switch's minute through the operating mechanism to meet the position, after installing the voltage controller may also implement the automated accent pressure, causes transformer's output voltage to stabilize in a scope.

37What does the oil bath in the formula transformer oil have to affect?

Answer: (1) insulates the function. The transformer oil as the insulation nature, causes between the winding and the winding, the level, as well as the winding and between the earth iron core and the fuel tank has the good insulation, thus enhanced device's insulation strength,

  (2) radiates the function. The transformer oil has in a big way compared to the heat capacity, simultaneously, is the oil-filled device has the good hot circulation loop, can run transformer's iron core and the winding and so on quantity of heat which disseminates, transmits to the cooling system, plays the valid radiation role.

  (3) blow-out action. In has carries in the regulating transformer, has carries in switch's insulating oil, has the blow-out function.

38In the oil bath type transformer, what characteristic all seals the transformer to have?

Answer: All seals the transformer, because has isolated the oil and the air contact way, insulates cannot be affected with damp, and the aging rate reduces greatly, the transformer use reliability and the service life therefore enhance. Before the run, cannot hang the core examination, the user will therefore save the expense. This kind of transformer's iron core, the coil and the body has outside the merit also to have the following craft and the structure is different: (1) the body uses the vacuum oil injection, clears the insulation to foresee accurately the moisture content and the air thoroughly, guarantees the transformer long-term service life. (2) the fuel tank uses the ripple type fuel tank or swollens shrinks the radiator, cancels the oil conservator. The oil volume's change adjusts the compensation by fuel tank's elasticity.

39, what does the transformer product perform experimental the target is?

Answer: The transformer experiments the target confirms the transformer performance whether to conform to the related standard and the engineering factor stipulation, detected whether in the manufacture to have the influence run each kind of flaw, moreover, through to tentative data's analysis, discovers the improvement design, enhances the craft the way.

40, what characteristic does the foil winding have?

Answer: The foil winding most major characteristic is: On the special-purpose braiding machine the volume system, the automaticity was high, has provided the high productivity and the product quality. The circle was the level, the longitudinal electric capacity is very big, eliminated the angle of spiral, anti-short circuit impact ability was quite strong, the mechanical strength was high, the construction was convenient, axial and the spoke was small to the error, the geometry size easy to guarantee, the circle was quite close, was not easy to have the air bubble, the surface is smooth.

41What is extinguishing coil's unique feature?

Answer: It in the structure is one kind of single-phase iron core reactor, it besides main coil, but also some uses for the record extinguishing coil movement the electric instrument coil, the electric instrument coil's fixed quantity all decides as the rated voltage100V, nominal current10A

42What does the extinguishing coil have in the electrical network to affect?

Answer: In the electric circuit, will flow the ground point electric capacity to produce the interrupted arc, under interrupted arc's function, in the electrical power system will present the overvoltage, will endanger possibly insulates the weak link, will create the accident to expand, to cause to the place interrupted arc to extinguish very quickly, must be the earth current charging induced current compensates the charging current. The extinguishing coil is uses in this target one kind of reactor.

Transformer craft knowledge

43rd, how many kinds does the transformer coil form have that?

Answer:

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