Pad-Mounted Transformers

Pad-Mounted Transformers

Pad-mounted transformers are units installed on a gravel or concrete base, with underground cable connections and restricted access. They are generally located in open public spaces, requiring a robust construction that prevents unauthorized access.

The design is carried out in accordance with the latest versions of ANSI/IEEE C57 and NEMA standards. Upon request, transformers with UL certification are also available.

Construction

HV and LV bushings are housed in an enclosure consisting of two compartments, where protection devices, the off-load tap changer, and other accessories are also located. In applications such as solar skids, LV bushings can be installed in a separate enclosure located on the short sides of the transformer (Segment 2 or Segment 4).

On the HV side, two types of bushings are available: deadfront and livefront. Livefront bushings include porcelain insulators with exposed live parts, while deadfront bushings are made of epoxy and use cable connectors, preventing exposure to energized components.

Main Features

Available dielectric options include mineral oil and natural ester (FR3). The transformer is equipped as standard with a pressure relief valve, pressure/vacuum gauge, dielectric thermometer, liquid level indicator, drain and sampling valves, off-load tap changer, load break switch (2 or 4 positions), and CLF fuses, bayonet type or expulsion type. Additional valves and indicators can also be supplied, with or without alarm contacts.

Technical Specifications

As transformers designed in accordance with ANSI/IEEE C57 and NEMA standards, the typical technical ranges for this product family are as follows. The rated power typically ranges from 15 kVA to 5,000 kVA. The high voltage side covers levels of 5 kV, 15 kV, 25 kV, and 35 kV, while the low voltage side is typically 120/240 V, 208Y/120 V, or 480Y/277 V depending on the required configuration. The operating frequency is 60 Hz in accordance with the North American market. The standard cooling type is ONAN (oil natural air natural). The off-load tap changer allows typical adjustments of ±2×2.5% or ±4×2.5% on the rated voltage. Efficiency levels comply with U.S. Department of Energy (DOE 2016) requirements where applicable.

For power ratings, voltages, or configurations outside these standard ranges, it is recommended to consult the specific project datasheet.