Abstract
For detection of AC voltage with non-contacting way, a potential transformer is widely utilized, However, when the voltage to be detected is low in the frequency or includes any DC component, the well-known problem of magnetically biased field or magnetic saturation is often experienced and does not put the high accurate detection into practice.
This paper discusses the voltage sensor which solves these problems and intends to achieve high accurate detection. The constitution is composed of the following procedures: (i) Generate a pair of positive and negative voltages in proportion to the voltage to be detected: (ii) Take out the positive and negative voltages from the voltage of (i) through an alternative switching of which frequency is sufficiently high compared with that of the voltage to be detected; (iii) Set the resultant voltage as a reference value for the voltage induced in the search coil arranged on the isolating transformer; (iv) Take the inverse operation of (i) to the secondary coil which is so wound as to make a close coupling with the search coil and reconstruct the original voltage to be detected. This sensor can also detect DC voltage.
The factors causing the detection error are, in general, due to both the existence of primary winding resistance, leakage inductances and magnetizing impedance as well as the dependence of these values on the magnitude and the frequency of the voltage to be detected. The proposed sensor reduces these effects. In practice, for ± 10 V full scale, the minimum detectable voltage is 10 mV when the % error of 0.08% is allowed.
