（節(jié)選）外文翻譯--傳導(dǎo)發(fā)射與傳導(dǎo)敏感度（英文）

1、CHAPTER SIXConducted Emissions and SusceptibilityIn this chapter we will investigate the mechanism by which emissions are generated and are conducted out of the product along the product’s ac power cord. Regulatory agenc

2、ies impose limits on these conducted emissions because they are placed on the commercial power system net of the installation. The commercial power distribution system in an installation is a large array of wires connect

3、ing the various power outlets from which the other electronic systems in the installation receive their ac power. It therefore represents a large “antenna” system from which these conducted emissions can radiate quite ef

4、ficiently, causing interference in the other electronic systems of the installation. Thus the conducted emissions may cause radiated emis- sion, which may then cause interference. Ordinarily, the reduction of these con-

5、ducted emissions is somewhat simpler than the reduction of radiated emissions since there is only one path for these emissions that needs to be controlled: the unit’s power cord. However, it is important to realize that

6、if a product fails to comply with the limits on conducted emissions, compliance with the limits on radiated emissions is a moot point! Therefore controlling conducted emissions of a product has equal priority with the co

7、ntrol of radiated emissions. Once again, manufacturers of electronic products realize that simply complying with the regulatory limits on conducted and radiated emissions does not represent a complete design from the sta

8、ndpoint of EMC. A product must be reasonably insen- sitive to disturbances that are present on the power system net in order to ensure reliable operation of the product. For example, lightning may strike the power trans-

9、 mission lines that feed power to the installation. This may cause disturbances that range from a complete loss of commercial power (which no product is expected to withstand) to momentary power loss due to power system

10、circuit breakers attempting to reclose (which a product is expected to withstand without loss ofIntroduction to Electromagnetic Compatibility, Second Edition, by Clayton R. Paul Copyright # 2006 John Wiley & Sons, In

11、c.136.1.1 The Line Impedance Stabilization Network (LISN)The purpose of the conducted emission test is to measure the noise currents that exit the product’s ac power cord conductors. These emissions could be simply measu

12、red with a current probe. However, the requirement that the measured data be correla- table between measurement sites may render this simple test unrealistic. The impe- dance seen looking into the ac power system wall ou

13、tlets varies considerably over the measurement frequency range and from outlet to outlet and building to building [1]. This variability in the loading presented to the product affects the amount of noise that is conducte

14、d out the power cord. In order to make this consistent between test sites, the impedance seen by the product looking out the product’s ac power cord must be stabilized from measurement site to measurement site. This is t

15、he first objective of the LISN—to present a constant impedance to the pro- duct’s power cord outlet over the frequency range of the conducted emission test. Also, the amount of noise that is present on the power system n

16、et varies from site to site. This “external” noise enters the product’s ac power cord, and, unless it is somehow excluded, will add to the measured conducted emissions. It is desired to measure only those conducted emiss

17、ions that are due to the product, and this gives the second objective of the LISN—to block conducted emissions that are not due to the product being tested so that only the conducted emissions of the product are measured

18、. Therefore the two objectives of the LISN are (1) to present a constant impedance (50 V) between the phase conductor and the safety wire (the “green wire”) and between the neutral conductor and the safety wire, and (2)

19、to prevent external conducted noise on the power system net from contami- nating the measurement. These two objectives are to be satisfied only over the fre- quency range of the conducted emission test (150 kHz–30 MHz).

20、Another subtle but unstated requirement for the LISN is that it be able to pass the 60 Hz (50 Hz) power required for operation of the product. The LISN specified for use in the conducted emission measurement is shown in

21、Fig. 6.2. The purpose of the 1 mF capacitors between phase and green wire and between neutral and green wire on the commercial power side is to divert “external noise” on the commercial power net and prevent that noise f

22、rom flowing through the measurement device and contaminating the test data. Similarly, the purpose of the 50-mH inductors is to block that noise. The purpose of the other 0.1-mF capacitors is to prevent any dc from overl

23、oading the input of the test receiver. It is instructive to compute the impedances of these elements at the lower frequency limit, 150 kHz, and the upper frequency limit, 30 MHz, of the FCC regulatory limit. These areEle

24、ment Z150 kHz Z30 MHz50 mH 47.1 V 9424.8 V 0.1 mF 10.61 V 0.053 V 1 mF 1.06 V 0.0053 VThus the capacitors are low impedances over the measurement frequency range, and the inductor presents a large impedance. The 1-kV res