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Präsentation zum Thema: "Sven Battermann, Heyno Garbe"— Präsentation transkript:
1Sven Battermann, Heyno Garbe COST 286Workshop'Impact of Communications Technology to EMC'PLC - Measurement of Mains CharacteristicsSven Battermann, Heyno GarbeInstitut für Grundlagen der Elektrotechnik und MesstechnikUniversität Hannover
2Overview Introduction – Description of the problem Interference scenarioDerivation of limits (CISPR )Idea and description of new measurement techniquesResults of STSM Barcelona/HannoverConclusions – new interesting work that has to be done
3Broadband communication networks with Primary task => Data transmissionLANDSL / ADSL / VDSL...with Secondary task => Data transmissionPLCISM-Applications – e.g. configuration of power drivesTotally different electrical characteristics of theused cables / lines!
4Mains used for telecommunication network Conversion to CMFed with DM-Mode220 V NetzRJ-45 orUSB to PCModemRJ-45 orUSB to PCModemConversion to CM
5Problems and known effects Observations:For EMC: Radiationdata rate decreases with distance from feed pointDifferent data rates in different roomsinfluence of load condition (used devices)Operation of “special” devices also decreases data rateQuestions:What are the reasons for this phenomenal experiences?What is the particular disturbance scenario?Quantification of mains influence possible?
7What is the problem with CM-currents? Two differential mode signals (DM also symmetric current) with 180° phase shift compensate! => low radiationThe common mode signal (CM also asymmetric current) will be radiated – without compensation!Problem: The fed DM-signal converts to a CM-Signal, if there are any asymmetries!
8Interference scenario broadbandtelecommunicationserviceShort-wave Service(e.g. broadcast)What is the interference scenario?CouplingLine guided interferenceField guided interferenceTransferfunction?
9Interference scenario - victim What is the impact of a common mode current on a connected device (receiver)?Power Supply –mains networkEd Hare: Radio frequency interference
10CM-current in the input circuit The common mode current flows through the input circuit of the receiver -> voltage drop at the input resistor-> interference
11Problem The limits used today have partially been defined in 1930. At that time narrowband interferers (transmitter) and stochastic broadband interferers (e. g. electric motors) have been known.Different situation today:Many telecommunication-services use a broadband spectrum up to the short-wave band.Different services are always on, therefore they are no stochastic interferers anymore.
12Influence on the limits? The limits (1930) are derived from the old interference scenario.The interference scenario changed significantly.Questions:Is it possible to model the situation today (with broadband telecommunication services) with the old interference scenario?It is reasoned to use the old limits, based on a different scenario for the interference scenario today?Is it possible to safeguard the radio services?
13Derivation of LimitsIt has to be expected that the use of the full limits of CISPR 22 cannot safeguard the protection of radio services anymore!What has to be done:For a valid protection of radio services a detailed analysis of the interference scenario is necessary.CISPR gives hints for the derivation of limits based on 10 influencing factors even under consideration of broadband services=> Rational derivation of limits.
14Influencing factors of CISPR 16-4-4 Quantification of probabilityDerivation of limits – just a value with a specified probability of a reception without disturbance.R actual signal-to-interference ratio, Rp Protection ratioSimultaneous use of interference source and victimUse of the same frequencyUse in a distance, that will allow disturbancesFull use of limits over large frequency ranges
15Interference scenario CISPR 16-4-4 Where is the back path for the common mode current?
16Worst case: Receiver with indoor antenna! Dipole outdoor antennaIndoor rod antenna
17Model of the transmission (channel model) Description with 2- and 4 port devices
18Measurements to be performed… What is a reasonable measurement setup?It is a „simple“ measurement problem – we just want to know the attenuation of the mains network between source and victim-> Mains Decoupling Factor-> Mains Attenuation FactorTwo port network analyser -> that’s it! – Really?
19Expansion of the modelGenerator withfeeding(source)Mains network with the used socketRadio with power supply(victim)???All 3 components have to be described in detail!
23Reasons for these measurements Why currents – what about well known CDNs with disturbance voltage measurement?Is the voltage the reason for the disturbance?What is the influence of the difference between CDN impedance against real mains impedance?Why don‘t you use a typical balun for telecommunication lines?Do we have 120 Ohm?Have you ever checked the characteristics of your balun with other loads than 120 Ohm?
24Receiver chassis: Flow of current Rod antennaCoupling network to mainsReceiver
25Feeding with comb-generator CM-chokebalunmainsGeneratorCounterpoisecurrent-probeCommon mode feedingDifferential mode feeding
28Mains Decoupling Factor Measured voltage at the radio dummy for both feedingsNormalized to the measurement voltage on the AMN
29Difference – Mains decoupling factor The constant impedance of the V-network is an ideal load for the balun.The measurements of the fed asym. to sym. (ICM‑VNetw) / (IN‑VNetw) current and the measured disturbance voltage at the V-network will show a minor frequency dependence.When the source will be connected with the mains the asym. (ICM-Mains) and sym. (IN-Mains) currents will change significantly due to the frequency dependent impedance of mains network and the resulting influence on the balun.
30Measurement with AMNDifferential mode feedingCommon mode feeding
34Conclusions Why doing near field measurements? – try to measure the most important quantity for the disturbance -> CurrentMeasurement Setup was presented during CISPR meeting in South Africa – (-> accepted! - Draft)What has to be done:noise floor measurements with radio dummymore attenuation measurements of mains networks