»  Design Capabilities & Facilities

Brush Transformers Gulf Design office is based on the technology and improvements taken in Brush transformers Limited UK Design department over 100 years. Brush Transformers Gulf Design office and Brush Transformer Limited UK Design office uses the same Electrical Design and Mechanical design programs , drawings and the both servers are synchronized and communicate with each other. Every transformer is made with actual dimensions in 3D ME-10 cad system package to ensure the correct fixing of all fittings and accessories.2D drawings are then produced from these 3D models for manufacturing and purchase purpose. 3D and 2D FEM analysis are used for Electromagnetic and Electrostatic distribution to finalize the winding, insulation and Core clamp structure design. The highly innovative and experienced design team makes sure the Brush design programs, and quality standards are used throughout the process.

 »  Magnetic Core

Three-phase transformers usually employ a three-leg core. Where transformers to be transported by rail are of large capacity, a five-leg core is used to keep them within the height limitation for transport. A two-leg core is well known for single-phase transformers. High-grade, grain-oriented silicon steel strip is used for the core materials. The main and side legs of the core are tightly bound by leg plate to the core clamps. Step lap mitered joints are used to achieve low noise and low no-load loss.

 »  Windings & Insulation

BRUSH has various types of winding structures; a high-series capacitance disc winding , Counter shield continuous disc winding, Helical, Layer etc. Their use depends upon the winding specifications. The windings are designed to have excellent resistance to lightning surges and their reliability is highly regarded by domestic and foreign utilities, from long-term service results. Both Kraft paper and thermally up graded paper covered conductors are used as per the requirement. CTC copper is also used as per the high current requirement. Winding and Insulation designs are checked with 2D FEM for Electrostatic analysis with different insulation arrangements. Major oil gaps such as High voltage to Low voltage, Phase to phase and Top Bottom insulations are subdivided by pre compressed press boards to provide high dielectric strength. Minor insulation such as turn to turn gap and conductor paper covering are checked by HSPT programs for Impulse distribution.

 »  Leakage Flux Measures

With the increase in transformer capacity, the leakage flux also rises, causing increased stray loss or local overheating. Brush understands the importance of estimating the correct leakage flux and to take measures to minimize stray loss. By using 3D electromagnetic FEM analysis leakage flux distribution   eddy current loss and circulating current loss on each part of the transformer can be estimated properly. Generally made of mild steel, tanks and other structural members have high permeability and are liable to invite leakage flux concentration. Thus, the tank inner surface is provided with a laminated shunts made of silicon steel strips to prevent leakage flux from penetrating the tank, thus reducing eddy current loss in steel members.

 »  Short Circuit Strength

Transformer windings are severely affected by electromagnetic force due to short-circuit currents passing through the windings. The current carried by the winding conductors (circumferential direction) interact with leakage flux and produces forces. The leakage flux is mostly in the axial direction (except in the ends of the windings) and hence the max radial force occurs around the mid height of the coils. Radial forces act outward on the outer winding and in ward on the inner winding. As the inner winding is exposed to buckling force, the core supports it securely and further bonded transposed stranded conductors are used to improve its hardness. For the outer winding, hardened copper conductors are used.

Near the ends of the windings a large part of the leakage flux bends towards the core leg and thereby causes a radial component of the flux. The interaction of this radial component of the flux with the winding current produces axial forces that tend to compress the winding conductors along the vertical axis. By estimating the proper force on coils the core clamp structure strength is designed to take care of these forces .By properly balancing the Ampere turns of LV and HV windings the imbalance axial force is minimized. Moreover, short-circuit tests have been conducted recently on one of our power transformer by KEMA in the Netherlands. It passed the tests successfully and the impedance variation in two phases is 0.0% and in one phase is 0.1% which shows the integrity of Design calculations and process followed by Brush Transformers Gulf.