Northern Power Transformers have either cover or sidewall mounted primary and secondary bushings. This allows for easy connection to overhead utility power lines or close coupling to switchgear, motor control, bus duct or other types of incoming and outgoing equipment. All units meet or exceed the design, manufacturing and testing requirements of CSA C88, ANSI C57 and IEC specifications.

Core & Coil
Northern uses a circular core and coil design to minimize the effects of short circuit. The cores are stacked using laminations precision sheared from high quality, grain-oriented electrical silicon steel. Corner joints may be of square cut or of mitered construction according to the sound level and losses specified. Five-limb cores and rectangular coils for star-star connected transformers, in the smaller ratings, use four-loop, wound type construction.

The coils are made of high conductivity, copper or aluminum conductor according to customer specifications. For low voltage, heavy current ratings, the windings are made from wide, thin strip conductors. For low current windings, paper or film insulated magnet wire is used. We also have experience in using CTC (Continuously Transposed Cable) for larger ratings.

Special attention is given to produce coils that can withstand the electrical stresses of lightning and switching surges during long and continuous duty. Multiple cooling ducts ensure a low coil temperature gradient thereby maximizing the life-span of the transformer.

All effective techniques such as magnetic tap balancing, multi-strand transposing, adhesive coated papers and coil compaction are employed to produce low loss coils having maximum strength. Strong "keep back" insulation is used on the outer layers of the HV windings along with proper mechanical bracing between winding sections to ensure adequate strength of the coil.

Core & Coil Assembly
The coils are installed on the cores using wood or TX board between the coil and clamp to resist the inward radial forces produced by fault currents and to reduce the effects of short circuit. Formed and welded core clamps, joined by tie roads from top to bottom, suitably braced to stop movement are used along with coil-end surge blocks, bus bar and cable support structures to produce a strong assembly.

Moisture is removed from the core and coil assembly by controlled process drying ovens to ensure the insulating material dries effectively to meet dielectric requirements prior to tanking. Each unit is put on full vacuum and the cooling fluid is completely de-aerated by slow admission through spray nozzle into the tank while maintaining full vacuum.

Tanks
All tanks are manufactured to withstand full field vacuum filling and are grit blasted and spray painted with high quality primers and paints. All metal fabrication including HV + LV Enclosures, throats, etc. are done at our own facility by our sister company Concord Prefab Inc.