Several Important Characteristics of Quality Factors of Series Resonant Circuit for Field Withstand Voltage Test

Guo Sen
HIMALAYAL - SHANGHAI - CHINA

Abstract: This paper analyzed quality factor - Q of series resonant circuit for withstand voltage test. Combined with the simulation test, reasons that affect the Q value were found out. Also, we made concrete investigation on equivalent loss resistance - R in the series resonant circuit and put forward new views.  

Key words: Quality factor, series resonant, voltage distribution

1.Introduction
Series resonant device is extensively applied in AC withstand voltage test of test object with large capacity on site, such as transformer and capacitor etc. Against common problems in the actual application, this article analyzes several factors, which have influence on factor quality - Q in the series resonant withstand voltage test. 

2.The Capacity of Test Object
Q-value is the most important parameter to evaluate series resonant circuit. It is in proportional to power frequency f and inductance L of high-voltage capacitor, and is inversely proportional to impedance R, which stands for active loss of the whole circuit. In a actual power frequency series resonant test circuit, based on the formula ωL=1/ωC, we can conclude that capacitive reactance determines inductive reactance. However, Q=ωL/R. If the test object is GIS or the equipment composed of independent elements, withstand voltage test can be conducted in section to improve the capacitive reactance and obtain higher Q-value. If variable frequency resonant device is used, the capacity of test object is greater and the resonant frequency is lower. In most cases, that is helpful for the test object.