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Proceedings CEEM'2009/Xi'an Experimental Research on Effects of LEMP on Power Circuits Zhou Xing, Wang Shuping, Wei Ming, Wang Qingguo (Electrostatic and Electromagnetic protection Research Institute, Ordnance engineering college, Shijiazhuang, Hebei 050005, China) Abstract: Two types of familiar DC power, switching power and integrated voltage regulator (IVR) power were chosen as study objects, the injection experiments and radiation experiments of LEMP on power circuits were studied and experimental results of injection and radiation were compared and discussed. The results show that injection method and radiation method are irrelevant, and not only injection effects but also radiation effects should be considered to estimate lightning effects. Key words: lightning electromagnetic pulse (LEMP); injection; radiation I Introduction Power supply circuit is the chief way in which the lightning disturbances enter the electric system, and about 70% disturbances of computer systems come from power lines [1, 2]. Lightning surge may be caused by direct lightning strikes, and also may be caused by lightning electromagnetic induction [3]. Nowadays most lightning defense standards aim at direct lightning strikes, but in fact more lightning surge caused by lightning electromagnetic induction [2]. So this paper chooses two familiar DC power circuits, adopts injection method and radiation method, study conduction interference and radiation interference of lighting surge to power circuits, and compares injection method and radiation method. IT Injection Experiments Lightning surge wave is a double exponential wave, and is commonly expressed as tl/t2. The tl is rise time of surge wave, and the t2 is surge pulse width. In this paper, lightning surge generator is LSG80I5 made in Japan, which can generate 1.2/50 u s surge prescribed in IEC standard 61000-4-5. the lightning surge can injection to AC input port of power on random phase at the rage of 0 ........ 2 n. A. Injection Experiment ofIVR Power Circuit IVR power circuit is shown in figure 1. The chip LM3I7 is a three-port adjustable integrated voltage regulator (IVR), and widely applied in power of digital circuit. In the experiments, the DC output voltage of IVR power is I2V, and the maximum output current is 500mA. Fig.l Circuit diagram of DC integrated power supply Injection experimental procedure is according to IEC standard 61000-4-5. When injection phase is 0, and injection voltage peak is -500V, the input and output voltage waves of transformer and LM3I7 are tested, and they are shown in figure 2 and figure 3. The lightning pulse has sharp rise edge and high peak-value, so it quickly caused magnetic core of power transformer saturation, and made surge pulse changed. So the output pulse of transformer is broadened and emerged a reverse sharp pulse as shown in figure 2. Figure 3 is the input and output waves of IVR LM3I7. Because of the distributing capacitance in the inner adjustor of LM317, the high-frequency part of input can get to output port through the capacitance Project supported by the NSFC No. 50877079 and 60671045 420

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Proceedings CEEM'2009/Xi'an

Experimental Research on Effects of LEMP on Power Circuits

Zhou Xing, Wang Shuping, Wei Ming, Wang Qingguo(Electrostatic and Electromagnetic protection Research Institute, Ordnance engineering college,

Shijiazhuang, Hebei 050005, China)

Abstract: Two types of familiar DC power,switching power and integrated voltageregulator (IVR) power were chosen as studyobjects, the injection experiments andradiation experiments of LEMP on powercircuits were studied and experimental resultsof injection and radiation were compared anddiscussed. The results show that injectionmethod and radiation method are irrelevant,and not only injection effects but alsoradiation effects should be considered toestimate lightning effects.Key words: lightning electromagnetic pulse(LEMP); injection; radiation

I Introduction

Power supply circuit is the chief way inwhich the lightning disturbances enter theelectric system, and about 70% disturbancesof computer systems come from power lines[1, 2]. Lightning surge may be caused bydirect lightning strikes, and also may becaused by lightning electromagneticinduction [3]. Nowadays most lightningdefense standards aim at direct lightningstrikes, but in fact more lightning surgecaused by lightning electromagneticinduction [2]. So this paper chooses twofamiliar DC power circuits, adopts injectionmethod and radiation method, studyconduction interference and radiationinterference of lighting surge to powercircuits, and compares injection method andradiation method.

IT Injection Experiments

Lightning surge wave is a doubleexponential wave, and is commonlyexpressed as tl/t2. The tl is rise time of surge

wave, and the t2 is surge pulse width. In thispaper, lightning surge generator is LSG80I5made in Japan, which can generate 1.2/50 u ssurge prescribed in IEC standard 61000-4-5.the lightning surge can injection to AC inputport of power on random phase at the rage of0........2 n .

A. Injection Experiment ofIVR Power Circuit

IVR power circuit is shown in figure 1.The chip LM3I7 is a three-port adjustableintegrated voltage regulator (IVR), andwidely applied in power of digital circuit. Inthe experiments, the DC output voltage ofIVR power is I2V, and the maximum outputcurrent is 500mA.

Fig.l Circuit diagram ofDC integrated powersupply

Injection experimental procedure isaccording to IEC standard 61000-4-5. Wheninjection phase is 0, and injection voltagepeak is -500V, the input and output voltagewaves of transformer and LM3I7 are tested,and they are shown in figure 2 and figure 3.The lightning pulse has sharp rise edge andhigh peak-value, so it quickly causedmagnetic core of power transformersaturation, and made surge pulse changed. Sothe output pulse of transformer is broadenedand emerged a reverse sharp pulse as shownin figure 2. Figure 3 is the input and outputwaves of IVR LM3I7. Because of thedistributing capacitance in the inner adjustorof LM317, the high-frequency part of inputcan get to output port through the capacitance

Project supported by the NSFC No. 50877079 and 60671045

420

Proceedings CEEM'2009/Xi'an

experimental switching power is 5~ and themaximum output current is IA.

The injection results of switching powerare different from that of IVR power. Theoutput wave of switching power circuit is twosegments of attenuation oscillating waves.The first segment continues more than IO~,and the second segment is later than the firstsegment 4o-80~s and continues severalmicroseconds. The second segment isinfluenced by injection peak voltage andinjection phase. The figure 4 shows theoutput waves at different injection phase. Thehigher is the total voltage of pulse and powervoltage at injection phase, the earlier thesecond segment wave occurred, the higheroscillating amplitude is, and the longerduration time is.

~.5

~ ~j5-400

--..----,---,------r----r----,-1.5

> :1- 0

~:~---,c__-c__-.----,..---,..--......____,-1.5

Fig.2 Input (above) and output (below) waves ofpower transformer

coupling, and the power filter of output porthas a distributing inductance, so it can't filterhigh frequency noise efficiently. Theforegoing reasons explain the DC output portwill gain some high frequency noise, and theexperimental results approved it.

~;H :.,~: ...:=~ 0 1 2 345

13~t/~S~ ::c::::=J:~:--~-----

-2 0 - 2r-----------,4--il-----riJ ----,1'0

t/~s

Fig.3 Input (above) and output (below) waves ofLM317

The DC output waves of IVR powercircuit is attenuation oscillating wave withduration of I r-...- 1.5~. Changing injectionphase and pulse peak-value, some contrastexperiments are studied. Experimental resultsshow different injection phase has littleinfluence on the effects of output port, andthe peak-value of injection pulse is higher,the fluctuation ofDC output is larger.

B. Injection Experiment of Switching PowerCircuit

Switching power has the virtues ofminiaturization, low weight, and highefficiency. The output voltage of

91tI4, 31t/4 q., 1t8

II'7

i~v1t/2~-, ,

372, ": I6 ;'1 ,

~5

4 I3

2I ' 51t/4 ., 71t14

10-20 0 20 40 60 80 100

t/ps

FigA Comparison of output waves of differentinjection phase when pulse peak is IkV

C. Comparison of Injection Effects of twoPower Circuits

In order to compare immunity of twopowers against injection pulse, somecomparing experiments are done at the sameinjection conditions. The table I showsexperimental results when injection phase isrt /2 at different injection voltages. Thevalues in the table are average values of 10times.

At the same injection voltage, thefluctuation of DC output wave of switchingpower circuit is larger than that of IVR powercircuit, and the output oscillating wave of

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Proceedings

IVR power only continues 1r-...-l.5~s, whilethe output oscillating wave of switchingpower has two segments, the first segmentcontinues more than 1Ous, and the secondsegment continues several microseconds.This result shows that the immunity of IVRpower circuit from EMP conductioninterference excel that of switching powercircuit.

Table 1 Voltage peak-peak values of output ports atdifferent injection voltages

Pulse200V 500V lkV 2kV 3kV

peak-valueIVR

0.57 1.54 3.21 6.95 10.49powerNSwitching 0.75 2.82 6.51 9.53 12.46powerN

ill Radiation Experiments

Radiation setup is composed of lightningsurge generator and parallel platetransmission cell (PPTC), which is shown infigure 5. At the center space of PPTC cansupply uniform field. Radiation source is alsolightning pulse with rise-time of 1.2~s andpulse-width of 50~s. The AC input line ofpower is put in the center of the PPTC, andabout I meter of power line is radiated bypulse field. Power circuit and its output portare shielded.

Tes t in g space

EUT

Fig.5 radiation test setup

A. Radiation Experiment of IVR PowerCircuit

The figure 6 is the testing input andoutput waves of power when radiation fieldstrength is 5kV/m. The input wave ishigh-frequency oscillating wave withduration of Ius, and the output wave is alsohigh-frequency oscillating wave with

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CEEM'2009/Xi'an

duration of 1 .2~s.

Changing radiation field strength andfield polity, some contrast experiments arestudied. Experimental results show thefluctuation of DC output and the fieldpeak-value is linear relation, and differentinjection phase has little influence on theeffects of output port. The power line istwisted-pair line, so it has no difference in upor down direction.

15

10

5

~ 0

> -6

·10

o 1 2 3 4 5 11.0 ---::0---::1---::2:--:3C--4~5-

tillS tillS

Fig.6 Input and output waves ofpower when E-fieldstrength peak is 5kV1m

B. Radiation Experiment ofSwitching PowerCircuit

The figure 7 is the testing input andoutput waves of power when radiation fieldstrength is 5kV/m. The waves are similar tothose of IVR power circuit.

306.0

205.5

10 I<: 0

1 1~<: 5.0

j l~~~"" " i ""'" .c~5 .10

4.5-20

-3Il 4.001234 5 012 345

tillS tillS

Fig.7 Input and output waves ofpower when E-fieldstrength peak is 5kVim

Similar to IVR power circuit, thefluctuation of DC output and the fieldpeak-value is linear relation, and differentinjection phase has little influence on theeffects ofoutput port.

e. Comparison of Radiation Effects of twoPower Circuits

In order to compare immunity of twopowers against radiation pulse, some

Proceedings

comparing experiments are done at the sameconditions. The table 2 shows experimentalresults at different radiation field strength.The values in the table are average values of10 times.

Table 2 Voltage peak-peak values of input andoutput ports at different field strength

Field 2.5 5 7.5 10 12.5strength/(kV/m)

Input14.73 27.45 37.05 46.69 60.26

IVR Npower Output

2.83 5.31 7.55 10.10 12.67N

SwitcInput

28.21 53.34 72.25 94.01 110.66hing

NOutputpower

N2.05 4.07 6.10 7.31 9.67

The coupling voltage of switching powersupply is higher than that of IVR powersupply at the same field-strength level,because the input impedance of switchingpower supply is higher, that is, the receivingcapacity of switching power supply is higher.But the voltage at DC output port ofswitching power supply is lower than IVRpower supply at the same field-strength level.This result indicates that the immunity ofswitching power circuit against radiationinterference is higher than that of IVR powercircuit.

N Conclusion

In radiation experiments, the inputcoupling waves are high-frequencyoscillating waves with duration of 1~ 1.5JlS,and because two types of power have badimmunity against high-frequency interference,voltage wave of DC output port of two typeof power supply resemble, which arehigh-frequency attenuation oscillating waveswith duration of 1~ 1.5Jls. At the samefield-strength level, the coupling voltage ofswitching power supply is higher than that ofIVR power supply, but the voltage at DCoutput port of switching power supply islower than IVR power supply. This resultindicates that the immunity of switching

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CEEM'2009/Xi'an

power circuit against radiation interference ishigher than that of IVR power circuit.

In injection experiments, the DC outputwaves of two type of power circuit aredifferent. The DC output waves of IVRpower circuit are oscillating waves withduration of 1r<:» 1.5Jls, and injection phase hasno influence on DC output. The output wavesof switching power circuit are two segmentsof oscillating waves. Each segment continueslonger than that of IVR power, and injectionphase has great influence on DC output. Atthe same injection voltage, the fluctuation ofDC output wave of switching power circuit islarger than that of IVR, power circuit, thisresult shows that the immunity of IVR powercircuit from EMP conduction interferenceexcel that of switching power circuit.

The above results show that injectionmethod and radiation method are irrelevant,and not only injection effects but alsoradiation effects should be considered toestimate lightning effects.

Reference:

[lJ He Limin. SCM Appliance Technology [M]. Beijing:Beijing Aviation and Spaceflight University publishingcompany,1993: 576'"-579.(in Chinese)

[2J Zhu Bangtian. Practical Anti-disturbing Technology ofElectronic Circuits [M]. Beijing: People's Posts andTelecommunications publishing company,1994.(inChinese)

[3] IEC 61000-4-5: Electromagnetic compatibility-Part 4-5:Testing and techniques-Surge immunity test, 1995.

[4] Yang Chunshan, Zhou Bihua. The method to generalizeengineering return stroke models. Proc Asia-Pasificconf on Environmental Electromagnetics, Hangzhou,China.2003,369......372.

[5] Chunshan Yang, Bihua Zhou, Cheng Gao, Lihua Shi.Modification of engineering return stroke models toinclude dispersion effects, IEEE Trans. Electromag.Compat, 2004,46 (3): 493--496.

[6] Chunshan Yang, and Bihua Zhou.Calculation Methods ofElectromagnetic Fields Very Close to Lightning. IEEETrans. Electromagn. Compat., 2004,46(1):133-141.