Showing papers on "Electromagnetic compatibility published in 1975"

Current zero measurement for circuit breaking phenomena

Abstract: This paper describes a new measuring method of the current zero phenomena of the circuit breaker with use of vacuum interrupter connected in parallel to the high resistance coaxial shunt. This method is applicable for the test circuit up to 50kA. The process is less effected by the electromagnetic induction offering a much accurate results. The measurements are conducted to obtain the V-A relation around current zero region of model SF 6 circuit breakers. The investigations on the transient time of the arc resistance, arc time constant and arc energy show that the arc time constant cannot be treated as a constant as the Mayr's equation is dealt.

Intrasystem Electromagnetic Compatibility Analysis Program

Abstract: The objective of IEMCAP, a computerized analysis program, is to facilitate the practical implementation of EMC at all stages of an Air Force system's life cycle, from conceptual studies of new systems £o field modification of old systems. This capability is applicable for use in ground, aircraft and space/ missile systems. The major areas to which this pro­ gram addresses itself in attaining this objective are specification generation, waiver analysis, design change evaluation, and trade-off analysis. To achieve all of the above tasks, the computer program is de­ signed with the flexibility to perform compatibility analysis at design stages ranging from a conceptual system configuration to a well-defined system.

Performance of electromagnetic shields in high voltage laboratories

Abstract: The paper constitutes a systematic investigation into the calculation and measurement of electromagnetic shielding effectiveness of high voltage laboratories. Both electromagnetic field and interference measurements were carried out to assess the shielding effectiveness of the UHV hall of Hydro-Quebec Institute of Research. While satisfactory shielding was obtained below 1 MHz, the measurements emphasized the deteriorating influence of seams and corners and revealed a considerable decline in shielding quality above a few MHz. A circuit approach is used to deduce new formulae for computing shielding effectiveness. Furthermore, new expressions are deduced for the increase in the equivalent resistance of a shielded enclosure due to non-uniform distribution of the circulating currents caused by intermittent bonding. A separate analysis is given for the shielding effectiveness above 1 MHz where in an UHV laboratory the dimensions of the enclosure approach the wave-length of the disturbing field. Considering the complex nature of the problem, agreement between theory and measurements is satisfactory.

Transfer Impedance Measurement as a Test for Electromagnetic Compatibility

Abstract: The shielding characteristics of Electromagnetic Interference (EMI) gaskets are difficult to measure and almost impossible to analyze theoretically. This is due to the fact that they are only a minor part of a larger system which distorts the field in which they are immersed and changes their physical dimensions. Thus, any attempt to evaluate gasket shielding proper­ ties has to be related to a defined enclosure of fixed dimensions in order to obtain consistent results. Fur­ thermore, if the enclosure is not selected properly, resonant effects which are difficult to characterize are introduced in the measuring setup.

An Overview of the Air Force Intrasystem Analysis Program (IAP)

Abstract: 1. The Intrasystem Electromagnetic Compatibility Analysis Program (IEMCAP), which will provide the basic computer analysis for the IAP for vulnerability assess­ ments, design of specification limits, compatibility and waiver analyses, and control of undesired electro­ magnetic energy in communications/electronic systems. It contains electromagnetic (EM) generator, transfer coupling, and receptor models.

Transmission Line Electromagnetic Compatibility

Abstract: The purpose of this paper is to provide a review of EMC problems commonly encountered by transmission line designers and to present a balanced approach to their solution. A comprehensive approach including both physical design parameters and EMC factors can be of vital assistance in determining the environmental impact of a line and in the overall design optimiza­ tion. The concept of criteria for various areas of exposure and levels of impact will be introduced. It should be noted that application of this approach is fundamentally governed by local conditions. The au­ thors have no desire to set criteria, but rather to suggest a methodology of solution.

Lightning Simulation Tests of Communication Cables

Abstract: F ive ty p es of sh ie ld e d co m m u n ica tio n c a b le s (w ith an o u te r in su la t in g c o v e r) , 180 f t . in len g th , w e re su b je c te d to the induced e le c tro m a g n e t ic f ie ld s due to a n e a rb y s im u ­ la te d l ig h tn in g s t ro k e . T he ligh tn ing s t r o k e w as an e l e c t r i ­ c a l a r c to g ro u n d due to th e d is c h a rg e of a h igh v o ltag e M a rx g e n e ra to r . M e a su re m e n ts of induced sh ie ld c u r r e n t , and s ig n a l co n d u c to r c u r r e n t s and v o lta g e s w e re m ad e fo r a s e r i e s o f cab le te rm in a t io n c o n d itio n s . T he co m m u n i­ c a tio n c a b le s te s te d w e re 50 p r . and 100 p r . te lephone c a b le s , 6 p r . and 12 p r . sh ie ld e d , t w i s t e d p a i r , a r m o r e d c a b le , and R G -11A /U c o ax ia l c ab le . E x tra p o la t in g the r e s u l t s of th e s e t e s t s , p e r fo rm e d w ith 11, 000 a m p e re s t r o k e s , to the l a r g e s t l ik e ly l ig h tn in g s t ro k e s (of 2 0 0 ,0 0 0 a m p e re s ) in d ic a te th a t the c o m m u n ica tio n cab le o u te r sh e a th (o r a r m o r ) m ay e a s i ly have ind u ced c u r r e n t s in th e 1000 a m p e re ra n g e . Induced v o ltag e m ay r e a c h 1000 v o lts b e tw een an in n e r co n d u c to r and g ro u n d and b e tw een c o n ­ d u c to rs of a tw is ted p a i r .

Considerations for Implementation of the Intrasystem Analysis Program

Abstract: schedule penalties. The lack of needed foresight in this approach leads to the next approach. This paper presents various considerations for the implementation of the Intrasystem Analysis Program (IAP) in EMC assurance. In general, the evolution of the EMC assurance process has been in the direction of earlier consideration of possible EMI; the use of IAP is another logical step in this evolution. The growth of IAP as an EMC tool will evolve in a manner similar to the EMC assurance process. After a period of preparation, initial IAP applications will be con­ centrated on system EMC situations in which equipment EMI characteristics are well-defined. Later, IAP analyses will include the modification of equipment EMI requirements based on IAP analysis of the equip­ ment in its intended system configuration. Eventually, after numerous applications of the IAP to equipment and system developments, the experience gained from use of IAP will be useful in modifying the EMC/EMI specifications and standards.

Pneumatic 'multivibrator' suitable for low electromagnetic interference applications (for potential measurement experiments)

Abstract: A pneumatic circuit has been developed to actuate repetitively any switching element lending itself to a reciprocating motion at a cycle period variable typically from 75-400 s. The device features operation free of electromagnetic transients. It is relatively inexpensive to fabricate and easy to operate.