IEVref:351-50-03ID:
Language:enStatus: Standard
Term: second-order lag element
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Definition: linear time-invariant transfer element the transfer function of which has exactly two poles with negative real parts which may be real or complex conjugate and no zeros

Note 1 to entry: The transfer function of a second-order lag element is given as

V( s ) U( s ) = K Ρ ( 1+ T 1 s )( 1+ T 2 s ) MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaamaalaaabaGaamOvamaabmaabaGaam4CaaGaayjkaiaawMcaaaqaaiaadwfadaqadaqaaiaadohaaiaawIcacaGLPaaaaaGaeyypa0ZaaSaaaeaacaWGlbWaaSbaaSqaaiaabg6aaeqaaaGcbaWaaeWaaeaacaaIXaGaey4kaSIaamivamaaBaaaleaacaaIXaaabeaakiabgwSixlaadohaaiaawIcacaGLPaaacqGHflY1daqadaqaaiaaigdacqGHRaWkcaWGubWaaSbaaSqaaiaaikdaaeqaaOGaeyyXICTaam4CaaGaayjkaiaawMcaaaaaaaa@5209@ for two real poles

and as

V( s ) U( s ) = K Ρ s 2 ω 0 2 +2ϑ s ω 0 +1 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaamaalaaabaGaamOvam aabmaabaGaam4CaaGaayjkaiaawMcaaaqaaiaadwfadaqadaqaaiaa dohaaiaawIcacaGLPaaaaaGaeyypa0ZaaSaaaeaacaWGlbWaaSbaaS qaaiaabg6aaeqaaaGcbaWaaSaaaeaacaWGZbWaaWbaaSqabeaacaaI YaaaaaGcbaGaeqyYdC3aa0baaSqaaiaaicdaaeaacaaIYaaaaaaaki abgUcaRiaaikdacqGHflY1cqaHrpGscqGHflY1daWcaaqaaiaadoha aeaacqaHjpWDdaWgaaWcbaGaaGimaaqabaaaaOGaey4kaSIaaGymaa aaaaa@520D@ for a complex conjugate pair of poles

where
KPis the proportional action coefficient;
T1, T2are the time constants;
ϑ MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiabeg9akbaa@36F5@ is the damping ratio;
ω0is the characteristic angular frequency;
sis the complex variable of the Laplace transform;
U(s)is the input transform;
V(s)is the output transform.

Note 2 to entry: This entry was numbered 351-28-14 in IEC 60050-351:2006.


Publication date:2013-11
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Internal notes:2013-12-16: de term corrected in accordance with mail from "Seeger, Anne" <anne.seeger@vde.com>, 2013-12-16. JGO

2017-08-28: <mstyle displaystyle=true'> corrected to <mstyle displaystyle='true'>. LMO
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