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It is often difficult to measure the saturation characteristics of the common-mode coil core (whole or part). Morning fly electrons show that the simplicity of the test can be seen to see how much of the attenuation of the common-mode filter is affected by the amount of inductance reduction caused by the 60Hz programming current. This test requires an oscilloscope and a differential mode suppression network (DMRN). First, monitor the line voltage with an oscilloscope. According to the following method from the oscilloscope A channel input signal, the oscilloscope time base set to 2ms / div, and then the trigger signal added to the A channel, the AC voltage reaches the peak when the cable current generated, then the filter performance degradation Is the expected thing. The input of the differential mode suppression network (DMRN) is connected to the LISN and the output is matched with 50 impedance and connected to the B channel of the oscilloscope. When the common mode choke coil operates in the linear region, the B channel monitors the transmit increase of no more than 6-10 dB during the input current fluctuation. Figure 1 shows the results of this test on the oscilloscope, the above curve for the choke coils emission; the following curve for the line voltage. During the peak voltage of the line, the bridge rectifier is conducting and conducting the charging current forward.

The demultiplexer of the common mode choke of choke coils manufacturers shown on the oscilloscope due to the 60 Hz charge current.

If the common mode choke is saturated, the emission will increase as the input surge increases. If the common mode choke reaches strong saturation, the emission intensity is the same as when the filter is not applied, that is to say it is easy to achieve more than 40dB.

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