Quadrature phase shifter for the measurement systems of testing of electrical insulation

Abstract

Quadrature phase shifters are widely used in practice of development of measurement systems intended for the measurements of dielectric dissipation factor and electrical capacitance. This article presents the examples of implementation of phase shifters intended to obtain the value of phase shift equal to 90º for the applying in measurement systems of monitoring and diagnosing the technical condition of electrical insulation. The developed solutions are based on applying of the analog signal multiplier implemented in the AD633 integrated circuit. The required value of phase shift is provided by adding a pre-shifted at a certain angle input harmonic signal to a signal with the reduced amplitude and the opposite initial phase. The article is also focused on the development of schematic solutions which can be used in order to remove the undesirable for many practical applications discrepancy between the amplitudes of the input and the output signals. This alignment of amplitudes is provided by the detection of their average rectified values with subsequent multiplication of their ratio by the shifted at 90º signal with the reduced amplitude. The designed schematic solutions imply the applying of analog circuits which contain the input phase shifter, low pass filter, voltage summing amplifier, two detectors of average rectified values, three analog multipliers and one voltage divider.