concept：
1、 The law of electromagnetic induction：
The size of the induced EMF (electromotive force) in the circuit is in direct proportion to the energy change rate which go through the circuit. (This is Faraday's law of electromagnetic induction.) Regardless of the method used, as the magnetic flux throuth the closed circuit changes, there is induced current generated in the closed circuit, and this phenomenon is called as electromagnetic induction.
2、 Lenz's Law：
Induced current has such a direction, that is, the magetic field of the induced current always result in the change of magnetic flux of the induced current, and that is what called Lenz's law.
3、 Energy conservation：
The energy will not produce without any foundation, and will not disappear without any foundation, it just transforms to another, or transfers from one object to another, and the total energy will not change during the process of transform or transfer. That is what called energy transform and conservation law. And the power is a measure of the energy transform.
4、Magnetic induction intensity：
The electricify straight wire which is perpendicular to the magnetic direction in the magnetic field, and what the ratio with the magnetic force (F), current (I), and the length of wire (l) is what called magnetic induction intensity. (B=F/IL, the unit of magnetic induction is decided by the unit of IL (F,I,L). In the internation unit system, the unit of magnetic strength is Tesla, T for short. The magnetic strength of 1M long wire through 1A current received is 1 Niu, and the magnetic strength is 1T. 1T=A*M/Niu).
5、 Magnetic line：
field in the direction of some of the curves. His point of the tangent direction Dugen the point of magnetic induction intensity the same direction. The magnetic line is some curves of direction produced in the magnetic field. The tangential direction of any poit in the curved shape is of the same as the direction of magnetic strength.
6、 Flux：
the flux Ø=BS (B is the geometric plane surface which is perpendicular to magnetic strength, S is the area). The meaning of flux can also be illustrated by the magnetic line. The increased number expressed by the flux is the magnetic lines of a certain surface of the magnetic field. In the International Unit System, the unit of flux is weber, and the symbol is Ø. 1Ø=BS. Than means magnetic strength equivalent to the magnetic flux through the unit are, and that's why magnetic strength is always called magnetic flux density. 1T=1Ø/m ²-Niu/A*M.
7、 power capacity：
The power of
transformer includes input power P1 and output power P2, the input power has something to do with the effeciency of the
transformer, and the supply
transformer power is an important basis to determine the size of the core.
8、 Power factor：
The ratio of input power to its voltammetry capacity of the
transformer is called power factor cosØ, and it has something to do with the magnetic current, the higher proportion of the magnetic current in the primary current, the lower of the power factor.
9、 efficiency：
The effeciency is the ration of output power (P2) to input power (P1).
10、 Voltage adjustment rate：
when the
transformer is from no-load to full load, because of that the voltage produced by the primary copper resistance r1,r2 is lowered by U1, U2 and thus making the load current is lower than no-load current, and the decline rate is stated by voltage adjustment rate. (voltage adjustment rate control the value of current density, and the output power is in direct proportion to the allow voltage adjustment rate).
11、 No-load current：
The
transformer no-load current is equvilant to the vector sum of magnetic current and iron loss. Phase separation of the magnetic current and iron loss is 90. For the small iron loss current, the main no-load current of the
transformer is the magnetic current. The no-load current is closely related to the performance of core: the bigger allowance of the no-load current and the higher magnetic strength value, and this can reduce the bulk of the
transformer. If the core is made of general performance material to reduce the cost, yet the no-load current will increase, and the power factor then drops, and thus affect the grid or power performance, the low allowance no-load current, the low core magnetic strength value, and that's why the core should apply the high performance materials.
12、 Temperature Rise：
When the
transformer comes into service, the coil working temperature is higher than the ambient temperature, and the temperature seperation is what called coil temperature rise. And the difference in temperature of the core working temperature and the ambient temperature is called core temperature rise. The temperature rise includes hottest-spot temperature rise and average temperature rise. And the coil average temperature rise is a index for the
transformer temperature rise. And temperature rise is an important parameter for the medium power or above power supply
transformers. The temperature rise dominates the value of the magnetic parameter and also affect the life of the
transformer.
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