Open-core Power Voltage Transformer: Concept, properties, application

Abstract

The Power Voltage Transformer, which is a singlephase unit used for direct conversion of power from high to low voltage, is becoming more and more relevant for substation application. This is why this paper aims to present the properties and advantages of the open-core design concept, which has been functioning very well for a number of years in inductive voltage and combined instrument transformers, enhancing the transformer reliability and operational safety. Furthermore, the intention is to list the known possible application options of these transformers and finally to succinctly point out the guidelines for future development, which would benefit both the manufacturer and the user.

Eddy current losses in power voltage transformer open-type cores

“…In the case of low frequencies, it is a reasonable approximation to assume that B ab remains constant across the thickness of a lamination sheet. In that case, by using equation ( 9), it becomes possible to explicitly express J abc in terms of B ab , as demonstrated in Ziger et al (2014). Consequently, the weak formulation term associated with J abc is modeled using B ab .…”

“…In this paper, the contribution of J αβγ in the 3D weak formulation will also be considered by using B αβ , but this transformation will be determined numerically through a 2D simulation in the preprocessing stage. Therefore, similar to Ziger et al (2014), for the homogenized magnetic reluctivity tensor ν follows ν = Re{ ν } + jIm{ ν }. Accordingly, the diagonal tensors that will define the characteristics of the new homogenized material are as follows: where individual components are calculated as: where K f is filling factor of a given laminated core.…”

“…Power transformers with open-type core offer several additional advantages over power transformers with conventional cores. These include simpler manufacturing, enhanced robustness, explosion-proof safety, reduced weight and significantly lower ferroresonance (Ziger et al , 2014; Lapthorn and Keenan, 2015). The use of the open-type core in combination with superconducting windings is being explored to reduce losses in windings (Liew and Bodger, 2001).…”

Calculation of the Eddy Current Losses in a Laminated Open-Type Transformer Core Based on the A→,T→−A→ Formulation

“…where J = J αβ + J αβγ holds. According to (7), the component of the magnetic induction perpendicular to the lamination sheets induces the current density J αβ , which only has tangential components with respect to the lamination sheets. On the other hand, the tangential component of magnetic induction, according to (8), induces eddy currents of density J αβγ which generally have all three spatial components, as shown in Figure 1.…”

“…In this paper, the focus is on open-type core transformers, which are commonly used for auxiliary power and rural electrification applications [7]. Here, an open-type core transformer is used as a power transformer; thus, eddy current losses represent an important parameter in the open-type core design phase [8,9].…”