EE13

What is the relationship between high frequency transformer power and frequency and iron core?

The power approximation of high frequency transformer is in direct proportion to core capacity and core cross-sectional area, 

ac frequency and core magnetic density,Actual output power

It's related to the wire diameter, and it's proportional to the size of the core window. With equation

Formula forWindow size * core area = (output power * traverse current)/(a coefficient * ac frequency * core magnetic density)，

This formula is more accurate. Another common but less accurate formula is (core cross-section area x magnetic density x lamination coefficient) squared

For the standard EI core, in the first formula, the window size is the same as the iron core cross-section area, and for the power frequency alternating 

current, it becomes

The second formula,Both of these formulas are empirical.

Suppose we are talking about a transformer, as is commonly known, whose core is made of a cold-rolled silicon steel sheet with high magnetic conductivity.

 Under this condition:

Frequency increase: the magnetic flux density in the core decreases proportionally, but under the same magnetic flux density, the higher the frequency, 

the greater the unit loss of the core.

When the two are combined, the result is a higher frequency and a lower unit loss of the core.

Core loss is the reduction of no-load loss.

Transformer efficiency A= output power P2/ input power P1= (input power P1- no-load loss P0- load loss PK)/ input power P1= (p1-p0-pk)/P1

Therefore, if other conditions remain unchanged, the frequency is increased. As the no-load loss P0 decreases and the output power P2 increases, 

the efficiency of the transformer increases.

The power of the transformer is related to the section area of iron core and the diameter of copper wire. The larger the section area is, the larger 

the window space is and the larger the diameter of copper wire is.

Transformer labeled 4 w, its core column cross-sectional area: S = 1.25 * square root of P = 1.25 * square root of 4 = 2.5 ㎡ (c)

The complete set of the ee13 by its bakelite bobbin+ferrite cores+copper wire+tape, the gap realated to its inductance, winding number ralated to the current.

EE13 have excellent temperature rise characteristics. Because of these characteristics, it can achieve very high current density in a very small package.

Tips 

Loss of the  ee13 transformer core

Hysteresis losses
It is proportional to the area of the dc hysteresis loop and linearly related to the frequency.

Eddy current loss Pc
The eddy current loss Pc=Cef2B2/ rho, where Ce is the dimensional constant rho is the resistivity on the measurement of frequency f. With the increase of frequency, the proportion of eddy current loss in the total loss increases gradually. When the operating frequency reaches 200~500kHZ, eddy current loss has taken a dominant position.
When adding ac voltage in core coil, through the exciting current in coil, excitation flux produced all the ampere-turns Φ through core section, if the core is the conductor, core itself will chain around us all secondary coil magnetic flux and constitute a single turn.
When ac excitation voltage U1, according to electromagnetic induction law, U1 = N1d Φ/d t, each turn induction electric potential, magnetic core section both large induction electric potential equivalent a turn around for the U1 / Φ N1 = d/d t.
Because the resistivity of the core material is not infinite, there is a certain resistance value along the periphery of the core, the induced voltage produces current ie, that is, eddy current, flow through this resistance causes loss, that is, eddy current loss.