Transformer is converted AC voltage, current and impedance of the device, when the primary coil has an alternating current, the core (or cores) in the alternating current magnetic flux arises, so that the voltage induced in the secondary coil (or current). Transformer comprises an iron core (or cores) and coil, the coil has two or more windings, wherein the power supply is called the primary coil winding, the secondary winding is called the rest of the winding. In the generator, either coil moves through the magnetic field or magnetic field moves through the stationary coil, can EMF in the coil, in both cases, the value of the flux are the same, but there is the number of magnetic flux intersecting the coil chain change, which is the principle of mutual induction. Transformer is a use of electromagnetic induction interaction, transform voltage, current and impedance devices.

An electrical transformer principle of electromagnetic induction, power transfer or transmit a signal from one circuit to another circuit,
How much energy transport is determined by the use of electrical power.

Function: The transformer is a static electrical equipment. It is based on the principle of electromagnetic induction, to a level of AC voltage and current into the same frequency of the other gradation voltage and current equipment. Role: converting an AC voltage, AC current and impedance conversion exchange.

Classification: 

Cooling by Category: Dry (self-cooling) transformers, oil (self-cooling) transformer, fluoride (evaporative cooling) transformer.
Moisture-proof way by Category: Open-type transformers, potting transformers, sealed transformers.
Press the core or coil structure Category: core-type transformer (Insert core, C-type core, ferrite core), shell-type transformer (Insert core, C-type core, ferrite core), ring-type transformers, transformer metal foil.
Press the Power Phase Classification: single-phase transformers, three phase transformers, multi-phase transformer.
By Application: power transformers, voltage transformers, audio transformers, frequency transformers, high frequency transformers, pulse transformers.
Operating frequency: transformer core loss vs. frequency great, it should be based on frequency of use to design and use, this frequency is called frequency.
Rated power: at a predetermined frequency and voltage, the transformer can be long-term work, without exceeding a predetermined temperature rise of the output power.
Rated voltage: refers to the coil of the transformer voltage permitted shall not be greater than the specified value at work.
Voltage ratio: refers to the ratio of the transformer primary and secondary voltages, there are differences between the no-load voltage ratio and load voltage ratio.
Load current: when the transformer secondary open primary is still a certain current, this part of the current is called the no-load current. No-load current by magnetizing current (flux generated) and iron loss current (caused by core loss) components. For 50Hz power transformer, the load current is substantially equal to the magnetizing current.
Load loss: refers to the transformer secondary open, measured in the primary power loss. The main loss is core loss, followed by the loss (copper loss) load current in the primary coil resistance of copper produced, this part of the loss is small.
Efficiency: the percentage of secondary and primary power P1 P2 power ratio. Generally larger transformer rated power, the higher the efficiency.
Insulation resistance: that between the coil transformers, insulation between the coils and the core. Insulation resistance and the level of performance, high and low temperature and moisture level are related to the use of insulating materials.

Principle Introduction:

Satons transformer Main applications of electromagnetic induction principle to work. Specifically: When the AC voltage is applied to the primary side of the transformer U1, current flows through the primary winding is I1, the current in the core will produce alternating magnetic flux, so that the primary winding and a secondary winding electromagnetically contact, according to the principle of electromagnetic induction alternating magnetic flux through the two windings will be induced electromotive force, which is proportional to the size of the maximum number of turns and the main flux, winding turns and more high voltage side, the side of a small number of turns low voltage, when the secondary side of the transformer is open, that is, no-load transformer, a secondary terminal voltage is proportional to the number of turns and a secondary winding, ie U1 / U2 = N1 / N2, but primary and secondary frequency remains the same, so for voltage variations.

Parameters:

Frequency response: Refers to the transformer secondary output voltage with the operating frequency characteristics.

Transformer principle:If the transformer is in the middle of the pass band frequency of the output voltage of U0, when the output voltage (input voltage remains constant) down to a frequency range 0.707U0 when called Satons transformer passband B.

Primary and secondary impedance ratio:Early transformer secondary access to proper impedance Ri and Ro, so early transformer secondary impedance matching, the ratio Ri and Ro are called primary and secondary impedance ratio. In the case of impedance matching transformer in the best condition, the maximum transmission efficiency.

Technical parameters:

Different types of transformers have corresponding technical requirements, available appropriate technical parameters indicate. The main technical parameters such as power transformers are: rated power, rated voltage and the voltage ratio, rated frequency, operating temperature levels, temperature, voltage regulation, insulation and moisture resistance. For the average frequency transformer main technical parameters are: the transformer ratio, frequency, nonlinear distortion, magnetic shielding and electrostatic shielding, efficiency

Voltage ratio:
Transformers line circle the number two respectively N1 and N2, N1 is the primary, N2 as the secondary. In the primary coil is an AC voltage in the secondary coil an induced electromotive force is generated at both ends. When N2> N1, its induced voltage than the voltage applied to the primary is even higher, such a transformer is called step-up transformer; when N2 <N1, the induced electromotive force of its primary lower than the applied voltage, the transformer called step-down transformer.
n = N1 / N2
Where n is called the voltage ratio (turns ratio). When n> 1, then the N1> N2, U1> U2, the transformer for step-down transformer. Otherwise it is step-up transformer.

Transformer Efficiency:
At rated power, output power and input power ratio of the transformer, called the efficiency of the transformer, ie
Where η is the efficiency of the transformer; P1 is the input power, P2 is the output power.
When the transformer output power P2 is equal to the input power P1, the efficiency η equal to 100%, the transformer will not produce any loss. But in fact this transformer is not. To generate the total loss of the transformer for power transmission, this loss mainly copper and iron losses. Copper loss refers to the loss caused by the transformer winding resistance. When the current through the coil resistance heating, a portion of electrical energy is transformed into thermal energy loss. General by the coil winding is made of insulated copper wire, so called copper loss.
Iron loss of the transformer comprises two aspects. First, the hysteresis loss, when the AC current through the transformer, the transformer silicon steel sheet by the magnetic field lines and the direction and magnitude also change, so that the internal molecular friction between the steel sheet, heat energy is released, and thus the loss of part of electrical energy, which is the hysteresis loss . Another is the eddy current loss, when the transformer work. There are magnetic field lines through the core, in a plane perpendicular to the magnetic field lines induced current is generated, since due to this current circulating in a closed loop is formed, and a spiral-shaped, it is known as eddy currents. The presence of the iron core vortex heat, energy consumption, this loss is called the eddy current loss.
Power level is closely related to the efficiency of the transformer and the transformer is usually greater the power consumption and output power than the smaller, the higher the efficiency. Conversely, the smaller the power, the lower the efficiency.