SPD has two waveforms, 10/350μs and 8/20μs. What do they mean? Let’s find out.
According to IEC standard, Class I SPD test adopts Class I waveform, and its impulse current characteristic parameters are lightning discharge current Iimp, specific energy W/R and energy Q, and its waveform is 10/350μs;
The 2-level SPD test uses a type II waveform, ie 8/20μs, and its inrush current characteristic parameters are composed of current (In or Imax) rise time T1 and half-peak time T2.
In the 10/350μs waveform, 10 means that the time for the lightning current to reach 90% of the peak value from 0 is 10 microseconds, and 350 means that the time for the lightning current to decay from 0 to the half-peak value (half of the peak value) is 350 microseconds.
In the 8/20μs waveform, 8 means that the time for the lightning current to reach 90% of the peak value from 0 is 8 microseconds, and 20 means that the time for the lightning current to decay from 0 to the half-peak value (half of the peak value) is 20 microseconds.
The difference between the two waveforms is that the current rise time and decay time of the 8/20μs waveform are fast, while the 10/350 waveform has a fast rise time and a slow decay time. The difference is that the lightning current energy corresponding to the 10/350μs waveform is much larger 8/ 20μs waveform, about 17~21 times.
The most direct impact of 10/350μs waveform and 8/20us waveform in the SPD production process is to determine the difference in the materials and structures used by the SPD.
The 8/20μs waveform takes a very short time from the generation of the traveling wave to the extinction. The damage to the SPD is mainly concentrated in the current stress shock, which has little effect on the deterioration speed of the SPD. Therefore, the second and subsequent levels of surge protectors All use varistors as internal leakage components.
Due to the long decay time of the 10/350μs waveform, in addition to the current stress, the most important effect on the SPD is that the output heat will cause great damage to the SPD. Although ordinary varistors can withstand the current stress impact , However, the heat generated by long-term work will sharply accelerate the deterioration of the varistor and seriously affect the service life of the SPD.
Therefore, most T1-level SPDs are used as internal discharge current components in the form of discharge tubes or gaps or a combination of the two.
The SPD, T1 grade produced by Fortsurge Tech Ltd. adopts the compound structure of gap pressure sensitive resistance, which has large flux, low voltage protection level, and automatic energy coordination function.
T2-level SPD has functions such as local and remote alarms, and has obtained CQC, TUV, CE and other certifications, and is widely used in rail transit, petrochemical, power systems, airports, hospitals, schools and other industries.