DIMENSIONS

Application
Padmounted transformers are designed and tested in accordance with ANSI C57.12.00 USA Standard General Requirements for Distribution, Power and Regulating Transformers and Shunt Reactors; ANSI C57.12.26 Three Phase Padmounted Transformers.

Tank Construction
A rugged steel tank made from high quality steel plate and reinforced with external bracing to provide extra strength and rigidity during shipping and operation is furnished on all distribution transformers.

The latest welding techniques and equipment combined with special black light testing of welds reduces the possibility of oil leaks.

Insulation
Only the highest quality 100% Kraft paper is used throughout the coil. It is thermally upgraded for increased overload capability. Units rated at 55° C use the same insulation and assure a 12% increase in KVA when operated at 65° C.

The quantity and location of insulation is computer designed and carefully assembled to assure the highest possible dielectric strength.

Core
The AREVA T&D core is a stacked core design which utilizes the highest quality electrical silicon steel. It is cut to assure maximum utilization of its properties of grain orientation. It is braced and secured to prevent shifting during shipment or normal operation.

A three legged core is used. This type of core construction benefits the user by providing lower losses, exciting current and overall operating costs.

Coil Construction
AREVA T&D has been a leader in the use of aluminum in both the primary and secondary of its transformers. Our experience has led to a regular wound coil which features an aluminum sheet wound secondary winding and a layer-wound primary winding using aluminum rectangular or round conductor.

The advantages of a sheet-wound secondary combined with uniform winding tension is evidenced in the short circuit strength of the transformer. The low voltage sheet-winding allows the electrical centers of the high voltage and low voltage windings to be easily aligned, thus virtually eliminating the vertical component of short circuit.

Uniform winding tensions and the resulting tight, compact coil, minimizes the possibility of coil telescoping should the vertical component of short circuit be present.

Core Clamp
The core clamp is made from heavy gauge steel that is assembled to the core and coil while under pressure.

Processing
The prime areas of processing are moisture and air removal. At AREVA T&D the core and coil assembly is thoroughly dried in drying oven and tested for power factor to insure complete moisture removal. The entire assembly is retightened while hot to correct for shrinkage. The unit is immediately tanked then put into a specially designed vacuum chamber where near vacuum is applied until all the trapped air is removed. The unit is then filled with de-gassed oil. The next step is to subject the transformer to standard tests which will confirm dielectric integrity. The final stage of processing is the pressure leak test which consists of applying 7 PSI of dry nitrogen to the final unit to assure a sealed tank. We now have a quality transformer made from quality components.

Standard Tests

• Resistance
• No load losses
• Load losses
• Impedance
• Exciting current
• Polarity
• Phase rotation
• Applied potential
• Induced potential
• Impulse test