Line Power vacuum pressure impregnated (VPI) transformers combine a performance proven dry-type transformer design with the environmental protection of a polyester coil encapsulation process. This combination ensures reliable transformer operation in hostile environments containing moisture, dust, dirt, chemicals and other contaminants.

The VPI process fully penetrates and seals the coils into a high strength composite unit for complete environmental protection. Since the coil protection is created using vacuum pressure impregnation rather than molding, maximum design flexibility is achieved to allow conformance to the most stringent application requirements.

The vacuum impregnation of the varnish eliminates winding voids to reduce corona generation due to insulation voids.
Benefits:

Line Power vs. Cast Coil
• Lower initial cost
• Flexibility of design
• Elimination of cracking concerns
• Higher thermal overload available
Cast = 17% @ 80 / 115° C rise
VPI = 30% @ 80 / 150° C rise
• Less weight for easier handling and installation
• Smaller dimensions to save valuable floor space
• Outstanding environmental protection

The Material
Line Power uses a polyester solvent varnish class H 220° C. The transformer is first baked to remove any traces of water, dipped in the varnish, baked, dipped and baked again.

Coil Construction
Coil construction is used to assure proper ventilation and maximum strength. Coils are constructed using a 220° C Nomex® insulation system that for many years has had proven performance in dielectric strength, temperature stability and long life. The high voltage coils are wound directly over the low voltage coils to form a complete assembly. The coil assembly is completely insulated and mechanically braced to pass all ANSI standard tests.

Epoxy Shielded Transformer
Take one high quality Line Power VPI transformer, add 1-2 mils or more of modified epoxy varnish and the result is a premium transformer ready to handle the really tough environments. The Line Power Epoxy Shielded transformer is ideal for environments polluted with refrigerants, askarel, mineral oil, acids, alkalies, salt water and high humidity. Even greater dielectric strength, mechanical integrity, and thermal endurance than VPI is now achievable.

Line Power uses high viscosity insulating epoxy. This specially formulated epoxy is designed for greater film dry thickness than most epoxies in use today. The epoxy used has a high percentage of solids, 50% by weight, yet has a relatively low cure weight. This unique combination allows high mechanical bond strength (7 lbs. helical coil) and a low overall unit weight.

Where your environmental concerns are the greatest, specify the best epoxy transformer on the market today - Line Power's Epoxy Shielded Transformer.

Mitered Cores
A mitered core is similar to a butt lap core arrangement made from cold rolled, grain-oriented silicon steel laminations with joints configured at 45° angles for purposes of reducing core losses and sound levels.

Types
• Hybrid Miter - Achieves better losses than butt-lap construction, however v-notching core machine not required. Some 90° angle configurations still exist.
• Full Miter - All angles at 45° for maximum reduction of flux. "V-notcher" required to achieve center cut.

Purpose
To better control flow of magnetic flux and reduce eddy currents.

Benefits
• Eliminate flux in cross grain directions which reduces core loss and exciting current values.
• Permits larger KVA rating for a given constrained size.

For a 2500 kVA miter-core transformer, you can save as much as $2000 per year* in energy costs as compared to a butt-lap core transformer of the same size!

Line Power Mfg. is the only manufacturer of mining electrical equipment that can offer this exclusive feature.

*Based on $.07 kWA energy costs.