Knowledge

Test Principle of Low Ffrequency Method using in CT Analyzer CTA-1000

Release Time : 2018-11-01  View Count :

CTA-1000 cT Analyzer compliance with standard <IEC60044 and <IEC61869>. and the standard basis for CT Analyzer measuring the excitation characteritics of iron cores by low frequency method is as follows:


From IEC standard, CT testing can be done in conditions lower in frequency than the rated to avoid secondary windings the risk of


failing to allow the terminal voltage. The only requirement is that the core has the same size on the magnetic flux.


IEC60044-6 standard formula using in CTA-1000 CT Analyzer for calculating the magnetic flux given by:


ψ(t)= [Uct(t)-Rct*lct(t)]dt+40


Where,


Rct: Secondary winding resistance


Uct(t): Secondary winding terminal voltage


lct: Secondary current


ψo: The initial flux Alternation


ψ(t): T the magnetic moment of the cross-linking


The definition of Core Voltage:


Uc(t)=Uct(t)-Rct*lct(t)


When the core voltage Uc(t) for the sinusoidal signal, core voltage RMS to meet:


Ucrms=w*ψm/V2=2*n*f*ψm/v2=4.44*f*4m


where:


f: For the sinusoidal signal frequency


As can be seen, the largest settlement in the same chain of magnetic flux ψm, the core is proportional to voltage and frequency.


Therefore, as long as the core has the same size on the magnetic flux, then the test CT can be lower than the rated frequency of the conduct, when the core voltage amplitude required to reduce the requirements, test power of ct analyzer to the secondary winding of the client voltage also be reduced accordingly. On the frequency of low-frequency test results can be rated after the conversion frequency in ct analyzer.


CTA-1000 CT Analyzer and its accessories are as follows: