the basic principles of power transformers

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Transformer to be used in almost all electronic products, it is simple in pr inciple but will be different requirements for the use of different occasions (different purposes) transformer winding process. The transformer\\ s main function: voltage conversion; impedance transformation; isolation; meter/">regulator (magnetic saturation transformer) used transformer core shape is generally E-type and C-type core.
The basic principle of the transformer

When a sinusoidal AC voltage U1 is added to both ends of the primary coil, the wires have alternating current I1 and produce alternating flux Ñ„1, along the core through the primary and secondary coils to form a closed magnetic circuit. Induction in the secondary coil mutual inductance potential U2 Ñ„1 will be on the primary coil induces a self-inductance of potential E1 E1 direction of the applied voltage U1 direction contrary while similar magnitude, thus limiting the size of the I1. You need in order to maintain the flux Ñ„1 the presence of a certain amount of power consumption, and the transformer itself has a certain degree of loss, although the secondary did not take the load, there are still current in the primary coil, the current known as the \"no-load current . \"
Secondary connected to the load, the secondary coil to produce current I2, and the resulting flux Ñ„2, Ñ„2 direction and Ñ„1 contrary, since the offset, so that the iron hearts of the total flux decreased, so that the primary self-inductance voltage E1 reduced, the result I1 increases, showing that the primary current is closely related to the secondary load. When the secondary load current increase I1 increase, Ñ„1, also increased, and Ñ„1 increase in just complements offset by Ñ„2 that part of the flux in order to maintain the total magnetic flux of the iron heart unchanged. If you do not consider the loss of the transformer, can be considered an ideal transformer secondary load power consumption is the primary power to obtain electric power. The transformer secondary voltage needs to be changed by changing the number of turns of the secondary coil, but can not be changed to allow the load power consumption.
Second, the transformer loss
When the transformer primary winding is energized, the coils which produce the flux in the core flow, because the core itself is also a conductor, this electric potential in the vertical at the magnetic field lines of the plane will be induction electric potential in the core of the section the formation of a closed loop to generate electricity, like a vortex of so called \"vortex\". The \"eddy current\" losses of the transformer to increase, and the increase in temperature rise of the transformer core heat transformer. Loss generated by the \"eddy current\" known as the \"iron loss\". Need another To wound transformer with a large number of copper wire, copper wire in the resistor, the current flows through this resistance will consume some power, this part of the loss, often turned into heat and consumption, we call such a loss is copper loss . Transformer temperature rise is mainly composed of iron and copper losses.
Transformer existence of iron loss and copper loss, the output power is always less than the input power, we have introduced an efficient parameter to this description of η = output power / input power.
Third, the material of the transformer
To wound a transformer, we must have a certain understanding about the material and transformer, for which I will introduce this knowledge.
A core material:
Adding silicon to reduce the conductivity of the steel, to increase the resistivity in the core material of transformers used iron tablets, low-silicon, silicon, steel, it can reduce the eddy current loss reduction it. We often referred to as the addition of silicon steel silicon steel, silicon steel sheet used in the quality of the transformer have a great relationship on the quality, the quality of the silicon steel sheet is usually used to represent the magnetic flux density B, B value of the general black iron tablets 6000-8000, low silicon for 9000-11000, high silicon 12000-16000
Two winding transformer is usually used materials
Enameled wire, sandbags line, silk covered wire, the most commonly used enameled wire. For the requirements of the wire, good conductivity, insulation paint has sufficient heat resistance, and there should be some corrosion resistance. Under normal circumstances the best Q2 models of high-strength polyester enameled wire.
3, insulating materials
Winding transformers, isolation between the coil frame, the isolation between the windings, insulation material to use, the general transformers framework materials available phenolic cardboard production available polyester film or telephone paper between layers for isolation, wi nding between available yellow wax cloth for isolation.
4, impregnated materials:
Transformer winding, but also over the last process, is impregnated with insulating paint, it can enhance the mechanical strength of the transformer, to improve the insulation performance, and extend the service life under normal circumstances, cresol varnish can be used as the impregnating material.
Electrical engineering Glossary
To learn electrical technology must have an understanding of the concept of physical quantities in electrical engineering, To this end I will be commonly used in electrical engineering term summary for comment:
A resistivity --- also known as resistivity or called specific resistance. Is the measure of a physical quantity of the conductive material performance is good or bad, the letter ρ, in units of ohm * mm sq / m. Numerically equal to the kind of material do 1 m long cross-sectional area of ??1 mm2 conductor temperature of 20C when th e resistance value, the greater the resistivity, the lower conductive properties. The resistivity of the material varies with temperature of the physical quantity, its value is equal to the temperature rise 1C, the resistivity increases with the original resistance of the resistivity ratio, usually letters α, in units of 1 / C.
2, the temperature coefficient of resistance ---- said that the physical quantities of the resistivity of a substance varies with temperature, its value is equal to the temperature rise 1C, the increase of the resistivity with the original resistivity ratio, usually with the letter α , in units of 1 / C.
3, the conductance ---- objects the ability of the conduction current is called conductivity. In the DC circuit, the value of the conductance is the reciprocal of the resistance value with the letter É¡ expressed in ohms.
4, the conductivity ---- also known as conductance, but also to measure a physical quantity of the mater ial conductive performance is good or bad. Size value is the reciprocal of the resistivity, with the letter γ, in units of m / ohm * mm square.
The potential difference, electromotive force ---- circuit caused by other forms of energy converted to electricity, called electromotive force or simply EMF. With the letter E, in volts.
6, the self-inductance ---- generated by this current when the current changes in the closed-loop through the loop flux change, so the induced electromotive force in the loop, this is called self-inductance phenomenon of induced electromotive force is called the self-inductance electromotive force.
7, the mutual inductance ---- If there are two coils are close to each other, the magnetic flux generated by the first coil current with only coil chain. When the first coil current changes, the flux and the second coil chain changes induced electromotive force generated in the second only coil. This phenomenon is called the mutual in ductance phenomenon.
8 the inductance ---- self-inductance and mutual inductance of the collectively.
9, the inductance ---- AC current inductor circuit, inductors impede the AC current role, which is called the inductance Lx, Lx = 2πfL.
10 capacitance ---- AC current to the capacitance of the circuit, capacitors hinder the exchange current role, which is called the capacitance, Cx, Cx = 1/12πfc.
11, the ripple current ---- size change over time, changing the orientation of current, called the pulsating current.
12, the maximum amplitude ---- alternating current in one cycle is called the amplitude.
13, the average of the average ---- alternating current refers to the ratio of the total charge flowing through the circuit within a certain period of time and that period of time. The sine of the average volume is usually corrected half-week average amplitude value: mean = 0.637 * amplitude values.
14, RMS ---- two of the same resistance device, the DC and AC, respectively, if after the same time, equal to the heat they emit, then put the size of this DC as a valid value of this AC. Valid values ??for the sinusoidal current is equal to 0.707 times its maximum value.
15, active ---- also known as average power. AC instantaneous power is not a constant value, the average power in a period called the active power, it is the power consumed by the resistor in the circuit section, the letter P, units of watts.
16, depending on the power ---- the resistance and reactance of the circuit, the product of voltage and current is called apparent power, the letter Ps watts.
17, reactive power ---- the energy in the circuit with inductance and capacitance of these energy storage devices in the half-cycle time, power supply energy into the magnetic field (or field) is kept up, the other half cycle time The energy saved the magnetic field (or field) returned to power. They are just the exchange of energy and p ower, and there is no real energy consumption. Amplitude values ??of the rate of exchange of energy and power is called reactive power. The letter Q, the unit of Chi.
18, the power factor ---- in the DC circuit, the voltage multiplied by current is the active power. However, in an AC circuit, voltage multiplied by current part of the apparent power, and can play a role for reactive power (active power) will be less than apparent power. Active power and apparent power is called power factor COSφ said.
19, the phase voltage ---- three-phase transmission line (FireWire) and the voltage between the neutral line called the phase voltage.
20, the size of the voltage between the line voltage lines ---- three-phase transmission line (FireWire) called the line voltage, line voltage is 1.73 times the phase voltage.
21, relative to the amount of ---- in electrical engineering, to indicate the vector magnitude and phase of the sinusoid is called a phasor, also kn own as the vector.
22, the strength of the magnetic flux ---- magnetic induction perpendicular to the direction of the magnetic field area of ??the product is called the magnetic flux with the letter φ, the unit for the Maxwell.
23, ---- per unit area on the magnetic flux density through the magnetic flux is called the magnetic flux density, with the letter B, the magnetic flux density and magnetic induction intensity is equal in value.
24, Reluctance ---- similar to the meaning of the resistance, reluctance magnetic circuit the flux from the impediment symbol Rm, in units of 1 / Hang.
25, the permeability ---- also known as the permeability coefficient, a coefficient is a measure of material\\ s magnetic performance, to the letter μ, unit Hang / m.
26 Hysteresis ---- ferromagnet in the repeated magnetization process, the magnetic flux density changes always lags behind the magnetic field strength, a phenomenon called hysteresis.
27, the hysteresis loop ---- in a magnetic field, the relationship between the ferromagnet the magnetic flux density and magnetic field strength available curve to represent, when the magnetizing field for the cycle of change, the relationship between the ferromagnet in magnetic flux density and magnetic field strength is a closed line, this closed line is called the hysteresis loop in Figure 1.
28, the shape of the basic magnetization curve ---- ferromagnet hysteresis loop with magnetic induction (or magnetic field strength) the maximum painting hysteresis loop of magnetic induction (or magnetic field strength) The values ??take different values, you get a series of hysteresis loops, connect the loop vertex of the curve is called the basic magnetization curve.
29, the hysteresis loss ---- on the alternating magnetic field in the ferromagnet, some power loss due to hysteresis, so that the ferromagnet fever, this loss is called hysteresis loss.
30, the breakdown --- in sulating material in electric field under the severe discharge or conductive phenomenon called breakdown.
31, the dielectric constant - also known as the dielectric constant, dielectric constant or permittivity, it is said that a factor of the insulation capability of the characteristics of the letter ε unit of the France / m.
32, the electromagnetic induction --- When the flux changes of the chain of a conductor, the conductor appeared electromotive force, a phenomenon called electromagnetic induction.
33, --- also known as skin effect, when the high-frequency current through a conductor, current will be concentrated at the conductor surface circulation of the skin effect, a phenomenon called the skin effect.