FOUR-TERMINAL IMPEDANCECURRENTTRANSFORMERBRIDGEWITH RESISTIVERATIOARM

The most widelyused ratiotransformer bridgetechniquesavailablefor comparing four-terminalimpedancesare reviewed. A new ratio transformerbridgetechni- que is then described.The ratio transform- er used in thismethod is a current trans- former. The four-terminalimpedancesare sup- pliedby means of thistransformerwith a well knowncurrent ratio.Thus,thenewbrid- ge is suitablefor measurementson four-ter- minal impedancesin high current.The bridge can have either resistiveor inductively coupledratioarm. The bridge,which is de- scribedin this paper, is thatone using resistiveratio arm. The most interestingapplications of the bridge,namelyin testinglarge cable conductors,largereactors for high cur- rent , and high current shunts,are present- ed in the paper. A prototypeof the new bridge,whichhas been developed,is brief- ly illustratedand obtainedexperimental re- sults are shortly discussed.Accuracy and in- herent advantagesof the techniqueare in- vestigatedas well. The simplicityof the bridgeand its accuracysatisfyboth re- search purposesand factorytest exigencies. The new applicationin the detection of core loss at high inductionis presently investigated.Furtherwork is stillin pro- gress in the developmentof thebridgewith inductivelycoupledratio arm, which seems to be very promisingfor highly accurate tests of current transformers, impedance standards,and in frequencyresponce tests as well.