The national standard for pulse group immunity test is gb/t17626.4, which is equivalent to the international standard iec61000-4-4.
Electrically fast pulse interference caused by the failure of the equipment mechanism according to foreign scholars on the pulse group interference caused by the failure of the mechanism of the equipment, the energy of a single pulse is smaller, and does not Failure of the equipment. But the pulse group interference signal on the equipment line junction capacitance charging, when the energy above accumulates to a certain extent, it may cause the line (and even the system) of the misoperation. Next we come together to understand the group pulse test need to pay attention to what and group pulse test tools needed, I hope that through our introduction, can bring you some help.
A group pulse test tools needed
Practice shows that a device is often a cable line, in a certain test voltage, a polarity is particularly sensitive. Experiments have shown that the signal line is much more sensitive to electrical fast pulse interference than the power line.
Effective measures for the equipment through the electric fast pulse test first we first analyze the interference injection method: eft interference signal is coupled to the main power line through the coupling decoupling network in the 33nf capacitance coupled to the top (and the signal or control cables are through the capacitance coupling clamps to impose interference, the equivalent capacitance is 100pf). For 33nf capacitance, its cut-off frequency of 100k, that is, 100khz above the interference signal can pass; and 100pf capacitance, the cut-off frequency of 30m, only allows 30mhz frequency above the interference through. The interference waveform of an electrically fast pulse is 5ns/50ns, with a repetition frequency of 5k, a pulse duration of 15ms, and a pulse group repetition period of 300ms. according to the Fourier transform, its spectrum is a discrete spectral line from 5k - 100m, and the distance of each spectral line is the repetition frequency of the pulse.
Knowing the above, the coupling capacitor that applies the interference plays the role of a high-pass filter, because the impedance of the capacitor decreases with the frequency, then the low-frequency components of the interference will not be coupled to the eut, and only higher frequency interference signals will enter the eut. when we are in the eut circuit and then add the ****-mode inductance (special attention should be paid to the fact that the ***-mode inductance must be added to the mains power supply. Inductance must be added to the main power line and its return line, otherwise saturation will occur so as not to achieve the purpose of attenuating the interference) can be attenuated out of some of the high-frequency interference components, because the impedance of the inductance with the increase in frequency and rise. Therefore, the only interference signal actually applied to the eut is the middle frequency portion.
Second, the group pulse test matters needing attention
Coupling capacitance and *** mode inductance composed of a lc series resonant circuit, resonance point at the amplitude of the strongest interference signals, and if this time the electric fast pulse waveform just in the zero point, then the eut in the resonance frequency will not have a problem; but if the resonance frequency just happens to occur in the peak pulse moment, then the eut will be very strong interference and thus failure. will be very strongly disturbed and thus fail.
So, according to what kind of interference frequency eut is sensitive to adjust the inductance of the **** mode inductor: increase the inductance value, the resonance frequency decreases, the lower frequency interference suppression effect is good; reduce the value of the inductance, the resonance frequency increases, the higher frequency interference suppression effect is obvious, so as to achieve the purpose of the group pulse test.