On Estimating the No-Load Current of High-Capacity Moving Coil Voltage Regulators

Abstract

Moving coil voltage regulators are intended for smooth variation of voltage in a wide range. In the 20th century, various design versions of such devices were developed, and their production was mastered around the world, including in Russia. The type of voltage regulators with a moving short-circuited (SC) coil has been most widely used. Today, the production of such regulators in Russia has been stopped, although the need for them in specialized fields of application, in particular, at research and testing laboratories, still remains quite high. Currently, the Ramensky Electrotechnical Plant Energiya conducts research and development works for constructing a new lineage of high-capacity moving SC coil voltage regulators in single-phase and three-phase versions. In view of the specific features relating to operating principle of moving SC coil voltage regulators, one of the key parameters of their design, which in many respects determines their characteristics, is the no-load current, which can make tens of percent of the rated current. Accordingly, effective designing of voltage regulators that would comply with target indicators and characteristics is only possible if there are tools for estimating the device no-load current with acceptable accuracy. The article describes the operating principle of a moving SC coil voltage regulator and reveals the relationship between its main characteristics and the no-load current. The well-known analytical approach to estimating the no-load current of the considered regulator type is briefly outlined. An interpretation of this approach for application to the prototype design of the regulator that is under development is described. Based on the regulator magnetic field 3D modeling by the finite element method using up-to-date dedicated software tools, a numerical method for estimating the device no-load current is proposed, the accuracy of which is several times better than that provided by the known methods. A comparison between the estimated and measured values of the no-load current of the prototype 100 kVA single-phase moving coil voltage regulator is given.