The working principle and advantages of nanocrystalline surge suppressor

Lingang Li 2024/07/17

Basic introduction

Nanocrystalline cores are widely used in switching power supply, inverter, EMC filtering and other fields, which can effectively suppress the peak noise caused by the rapid change of current. The spike suppressor is usually made of a magnetic core with one or a few turns of copper wire. The structure and installation are very simple, but the suppression of spike noise is very effective.

Nanocrystalline core with high rectangular ratio has a very low core loss and very high permeability, and its inductance is very large when the current is very small. This large inductance effectively blocks the reverse reset current generated by the diode. This material can quickly reach saturation at a very small current.

Application diagram: (The red : peak suppressors )

Function and basic working principle of spike suppressor

Figure 1: current through diode without spike suppressor

Figure 2: current through diode with spike suppressor.

Figure 3: peak suppression Hysteresis loop diagram of spike suppressor (working process principle)

Figure 3 shows the hysteresis loop of nanocrystalline core material. The working process of the spike suppressor as follows: before reaching 1 point (when the current is turned on), the magnetic core is saturated and has a very low inductance. When the current is off, the working point reaches remanence point 2. The reverse recovery effect of the diode makes the current continue to decrease in the direction less than zero. Because amorphous material has a very high permeability at this time, its inductance is very large, so it can effectively suppress the peak current of the diode (Figure 2 shows the current after suppression),. IR is the theoretical reverse current peak, corresponding to the theoretical working point 3. however, due to the high inductance value of the peak suppressor, the magnetic core is prevented from reaching the theoretical working point 3 and remains at the reverse remanence point 4. Then it is magnetized to start another cycle.

Parameters required for basic design and calculation formula

Take the voltage calculation method as an example:

U=dφ/dt

Integrating on both sides of an equation

∫Udt=∫(dφ/dt) dt

∫Udt=∫dφ

φ=NBS

N= Turns

B= Magnetic flux density . In this formula B=Br

S= Effective cross-sectional of core.

According to the formula, the area surrounded by points 2-3-4 is equal to the core magnetic flux required to suppress surge.

So it follows that:, N*Br*S ＞∫Udt

During design, attention shall be paid to:

The continuous working temperature of nanocrystalline magnetic core shall not exceed 150 ℃.

Accurate calculation mainly depends on the correct value of diode reverse recovery time tr. It is affected by temperature and di/dt during operation. The di/dt value is determined by the inductance value of the line (including the variable inductance of the peak suppressor).

For more details on nanocrystalline cores or nanocrystalline surge suppressor, please feel free to contact us.

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