magnetic saturation

When we produce high frequency transformer, we often encounter such customer complaint - magnetic saturation. However, in fact, such undesirable phenomena are hard to find in the process of our production, because the number of turns, inductance, leakage inductance and other items that we often test cannot be detected by the comprehensive tester, and the harm of magnetic saturation is very large, which will cause us great losses. It may result in the scrapping of batch products. Cause client product explosion, etc
 
First, we need to understand what magnetic saturation is
Generally speaking, just like adding sugar to a cup of water, sugar is dissolved by water, but when there is too much sugar, the water can no longer dissolve the added sugar. That is to say, the sugar in this cup of water has been "saturated" after more sugar can be dissolved in this cup of water. In the same way, the current produces a magnetic field. In the process of transformer operation, the current and voltage increase, and the magnetic field strength also increases. However, when the magnetic field in the magnetic conducting body of the transformer reaches a certain level, the increase of current can no longer increase the magnetic field strength. At this time, it is considered that the saturation current of the transformer is the current intensity when the transformer reaches "magnetic saturation". Generally speaking, when the working current of the inductor exceeds the saturation current, or the permeability of the conducting magnet (such as the core of the transformer) is too low and the volume is not enough (the density of the magnetic field line is too large), it is easy to cause the magnetic saturation. Simply put, if a core coil is added with current, the generated magnetic field will be strengthened as the current increases. When the current reaches a certain degree, the generated magnetic field will not continue to strengthen, at this time, the core and coil will enter the saturation area, and the core will be in the saturation state.
 
Harm of magnetic saturation
The primary current of the transformer has saturated the core. From the perspective of energy transfer, the primary energy cannot be transferred to the secondary. Similarly, if it is a coil, the self induction in the saturated state will be greatly reduced or even disappear, and the inductance will be reduced or disappear. The rest is the DC resistance of the coil. Of course, the current passing through will increase, leading to the connected device Parts are damaged due to overcurrent. 1 - the primary side of the transformer is heated or even blasted. 2-The transformer does not work. 3-The transformer burned MOSFET or even circuit board due to open circuit. 4 - due to the saturation of the transformer, the actual power of the customer's product cannot reach the design power
 
How can we avoid the harm of magnetic saturation?
Because we are usually in the production process of static testing, and the general test items can not detect such defective products. It is often that all tests are qualified in the factory, but when it comes to the client, there is a blow up, overheating or the output power of the transformer designed by the client can not reach. So it needs to be done 1 - since the magnetic saturation is related to the permeability of the core, try to use the core with high permeability (which will increase the cost of course). 2 - strictly follow the customer's acknowledgment and operation instructions, and do not change materials without the customer's consent. 3 - in case of similar defects, actively communicate with customer engineering, adjust the proportion of primary stage turns, and increase the air gap depth of the core