A Novel Approach for Evaluating Eddy Current Loss in Wind Turbine Generator Step-Up Transformers

Abstract

South Africa is aiming to achieve a generation capacity of about 11.4GW through wind energy systems, which will contribute nearly 15.1% of the country's energy mix by 2030. Wind energy is one of the principal renewable energy determinations by the South African government, owing to affluent heavy winds in vast and remote coastal areas. In the design of newfangled Wind Turbine Generator Step-Up (WTGSU) transformers, all feasible measures are now being made to drive the optimal use of active components with the purpose to raise frugality and to lighten the weight of these transformers. This undertaking is allied with numerous challenges and one of them, which is particularly theoretical, is delineated by the Eddy currents. Many times the transformer manufacturer and also the buyer will be inclined to come to terms with some shortcomings triggered by Eddy currents. Still and all, it is critical to understand where Eddy currents emanate and the amount of losses and wherefore the temperature rise that may be produced in various active part components of WTGSU transformers. This is the most ideal choice to inhibit potential failure of WTGSU transformers arising from excessive heating especially under distorted harmonic load conditions. In the current work, an extension of the author's previous work, new analytical formulae for the Eddy loss computation in WTGSU transformer winding conductors have been explicitly derived, with appropriate contemplation of the fundamental and harmonic load current. These formulae allow the distribution of the skin effect and computation of the winding Eddy losses as a result of individual harmonics in the winding conductors. These results can be utilized to enhance the design of WTGSU transformers and consequently minimize the generation of hotspots in metallic structures.

Stray Load Loss Valuation in Electrical Transformers: A Review

“…In core-type transformers, the HV and LV windings are cylinders with a common centre encircling vertical magnetic core limbs with circular cross-sections [60]. The vertical magnetic core limbs and the horizontal core yoke components are made of thin laminated sheets and provide a magnetic flux circuit.…”

“…The field composition generated by the load current is illustrated in Figure 6, which is a two-dimensional model of the transformer active part components as indicated [60]. Individual winding conductors encompassed by alternating electromagnetic fields encounter an internally induced voltage that triggers the generation of the winding Eddy currents to flow in respective winding conductors [60]. These currents bring out losses in the conductors and are dissipated inherently as heat, generating a rise in temperature in the conductors and surrounding metallic structures.…”

“…If load current flows within the winding copper conductors, a loss (I2R) will be generated. The individual current-carrying conductors are encompassed by alternating electromagnetic fields with an intensity proportional to the load current [60]. The field composition generated by the load current is illustrated in Figure 6, which is a two-dimensional model of the transformer active part components as indicated [60].…”

“…The individual current-carrying conductors are encompassed by alternating electromagnetic fields with an intensity proportional to the load current [60]. The field composition generated by the load current is illustrated in Figure 6, which is a two-dimensional model of the transformer active part components as indicated [60]. Individual winding conductors encompassed by alternating electromagnetic fields encounter an internally induced voltage that triggers the generation of the winding Eddy currents to flow in respective winding conductors [60].…”

“…The additional losses outside the copper loss are by and large described as the stray losses. Even though the additional losses are Eddy current losses, only the fraction in the windings is described as the "winding Eddy loss", and the remaining loss component is contributed by the metallic active parts and can be described as the "other stray losses" [60]. The winding Eddy losses are directly proportional to the load current that produces the electromagnetic fields and the square of the fundamental frequency (50 Hz) [60].…”