Scope:
•Rated capacity: 112.5 kVA Through 15,000 kVA
•Primary Voltage : 600V Through 35 kV
•Secondary Voltage: 120V Through 15 kV
Vacuum Pressure Impregnation (V.P.I) is a process by which a fully wound electric apparatus stator or rotor is completely submerged in a resin. Through a combination of dry and wet vacuum and pressure cycles, the resin is assimilated throughout the insulation system. Once thermally processed, the impregnated windings become a monolithic and homogenous structure.
VPI dry type transformers are ideal for most industrial and commercial applications. These transformers provide excellent mechanical and short-circuit strength, no danger of fire or explosion, no liquids to leak, less weight than comparable cast coil units, low total ownership costs and low initial costs. They use a UL listed 220°C insulation system, regardless of temperature rating. Low installation, maintenance and operation costs make VPI transformers a solid investment.
VPI transformers are non-explosive with high resistance to flame and do not require vaults, containment dikes, or expensive fire suppression systems.
The VPI Process
VPI transformer coils are vacuum pressure impregnated in high temperature polyester varnish. The process includes complete submersion in varnish under vacuum and pressure and regulated curing using statistically process controlled equipment to ensure consistency.
The finished coils are effectively protected against moisture, dirt, and most industrial contaminants. JIEZOU POWER’s VPI transformers are generally suitable for use indoors or outdoors where people work and breathe.
A 220℃ Class UL Listed insulation system is used on JIEZOU POWER’s VPI transformers regardless of specified temperature rating. This system accommodates a standard temperature rise of 150℃. Optional temperature rises of 80℃ and 115℃ and fan cooling allow for unsurpassed overload capacity.
VPI transformers offer design flexibility and are constantly used for power upgrades and retrofit designs.
Core Construction
VPI transformers utilize a step-lap in mitered core construction to ensure optimum performance and minimal sound levels. The mitered core joints allow efficient flux transfer along natural grain lines between the core legs and yoke. The step-lap construction further enhances the efficiency of the joint by reducing joint fringing, which reduces core losses and exciting current.
The core is designed and built to provide the lowest possible losses from the effects of magnetic hysteresis and eddy currents. All possible steps are taken to prevent local circulating currents and to avoid built-in bending stresses.
The core is manufactured from high permeability, cold-rolled, grain oriented silicon steel. Magnetic flux densities are kept well below the saturation point. The steel is precision cut to assure that it will be smooth and burr-free. For rigidity and support, the upper and lower yokes are solidly clamped with steel support members. Tie plates connect the top and bottom clamps and provide a rigid structure for lifting.
The finished core is coated with a corrosion resistant sealant which provides lamination cohesion and protection for moderate to harsh environments.
Coil Construction
Winding design need not be specified unless there is a customer preference. JIEZOU POWER optimizes winding construction for operating voltage, basic impulse level, and current capacity of the individual winding.
Whenever possible, transformers are constructed with sheet wound secondary windings and wire wound primary windings.
Winding construction may be either round or rectangular through 2500 kVA for VPI coils. Windings on VPI transformers with ratings greater than 2500 kVA are typically round.
JIEZOU POWER’s low voltage VPI windings, insulation class 1.2 kV (600V) and below, are typically wound using sheet conductors. This construction allows free current distribution within the axial width of the coil which eliminates the axial forces developed in other types of windings under short circuit conditions.
The primary coil is wound directly over the secondary coil and is separated by an insulating barrier. Aluminum conductors are standard with copper offered as an option.
Post time: Aug-19-2024