Basic knowledge of transformer
Transformers are used in almost all electronic products. Its principle is simple but
According to different use occasions
The winding process of the transformer will be different
Claim. The main functions of the transformer are: voltage transformation; impedance transformation; isolation; voltage stabilization (magnetic
Saturation transformer), etc. The core shapes commonly used in transformers generally have
Type iron core.
One, the basic principle of the transformer
Is a simplified diagram of the principle of a transformer,
When a sinusoidal AC voltage
When added to both ends of the primary coil,
In the wire
And produce alternating magnetic flux
, It passes through the primary coil and the secondary coil along the core to form a closed magnetic circuit. In time
Mutual induction potential is induced in the first coil
Will also induce a self-induced potential on the primary coil
The direction of
The direction is opposite but the amplitude is similar,
the size of.
In order to maintain the magnetic flux
Need to have a
Certain power consumption,
And the transformer itself also has a certain loss,
Although the secondary is not connected to the load at this time,
There is still a certain amount in the primary coil
This current is called "no-load current".
If the secondary is connected to a load, the secondary coil will generate current
, And therefore generate magnetic flux
The direction of
Play a role in canceling each other, so that the total magnetic flux in the core is reduced, so that the primary self-inductance voltage
Reduced, as a result
Increase, it can be seen that the primary current is closely related to the secondary load. When the secondary load current increases
The added part just complements the
The part of the magnetic flux that is canceled,
To keep the total magnetic flux in the core unchanged.
Consider the loss of the transformer,
It can be considered that the power consumed by the secondary load of an ideal transformer is the power that the primary draws from the power supply.
The transformer can change the secondary voltage by changing the number of turns of the secondary coil as needed.
But the allowable load consumption cannot be changed
Second, the loss of the transformer
When the primary winding of the transformer is energized, the magnetic flux generated by the coil flows in the iron core, because the iron core itself is also a conductor.
In a plane perpendicular to the lines of magnetic force, an electric potential is induced,
This potential forms a closed loop on the cross section of the core and generates current,
it is good
It is like a vortex so it is called "vortex".
This "eddy current" increases the loss of the transformer,
And make the core of the transformer heat up
The temperature rise of the compressor increases.
The loss caused by "eddy current" is called "iron loss".
In addition to winding the transformer, a large amount of
These copper wires have resistance,
This resistor will consume a certain amount of power when current flows.
This part of the loss often turns into heat
As for consumption, we call this loss "copper loss". Therefore, the temperature rise of the transformer is mainly caused by iron loss and copper loss.
Since the transformer has iron loss and copper loss, its output power will always be less than the input power. For this reason, we have introduced
An efficiency parameter to describe this,
Three, the material of the transformer
To wind a transformer, we must have a certain understanding of the materials related to the transformer. For this reason, I will introduce
Some knowledge in this area.
, Core material:
The core materials used in transformers are mainly iron sheets, low silicon sheets, and high silicon sheets. The addition of silicon to the steel sheets can reduce the conduction of the steel sheets.
Electricity, increase the resistivity, it can reduce the eddy current and reduce its loss. We usually call silicon-added steel sheets as silicon steel sheets.
The quality of the silicon steel sheet used in the quality of the device has a great relationship,
The quality of silicon steel sheet usually uses magnetic flux density
General black iron
, Low silicon wafer is
, High silicon wafer is
, The materials commonly used for winding transformers are
Enameled wire, sand-bag wire, silk-covered wire, the most commonly used enameled wire. The requirements for wires are good electrical conductivity and insulating paint
The layer has sufficient heat resistance and a certain degree of corrosion resistance. Best to use under normal circumstances
Model of high-strength polyester paint
In the winding transformer, the isolation between the coil frame layers and the isolation between the winding resistances all use insulating materials.
The frame material of the press can be made of phenolic cardboard,
The layers can be separated by polyester film or telephone paper,
The winding room can be isolated by yellow wax cloth.
, Impregnation material: