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The 25 kVA single phase pole mounted transformer serves a village distribution spur or a row of small commercial units along a rural road. It commonly supplies a few shop units, a workshop, a water booster and a bank branch from one overhead position. Because it hangs on the cross-arm, the footprint at ground level stays clear for traffic and drainage.
Windings on the 25 kVA single phase pole mounted transformer are wound from aluminium or copper conductor over a grain-oriented electrical steel core, with insulation rated to the impulse level of the primary class. Impedance voltage falls between 1.1 and 5.75 percent, the tank is mild or stainless steel, and the paint finish is matched to the utility colour scheme.
Rated Capacity | 25 kVA |
Type | CSP Type / Conventional Type |
Rated Primary Voltage | 2.4-34.5 kV or Customized |
Secondary Voltage | Customized |
Frequency | 50/60 Hz |
Vector Group | Ii0, Ii6 |
HV Tap Changer | ± 2×2.5% HV taps |
BIL | 30-150kV |
Efficiency | DOE 2016/CSA/IEEE/GB |
Impedance Voltage | 1.1-5.75% |
Cooling Method | ONAN/ KNAN |
Operation | Step Down |
Standards/Certificate | IEEE, ANSI, IEC, CSA, NEMA, ISO, CE |
Application | Residential/commercial/small industry/power distribution systems |
Altitude | ≤1,000 m, 1000–2000 m, 2000–3000 m, >3000 m |
Transformer Oil | Mineral Oil or FR3 |
Winding Material | Aluminum/Copper |
Core Material | Grain-Oriented Electrical Steel |
Color | Customized |
Tank Material | Mild Steel / Stainless Steel |
The core is stacked from grain-oriented electrical steel and clamped into a closed magnetic circuit. Mitered joints and a single-point core ground hold no-load loss and sound level down, which matters on a pole where the unit runs unattended for years.
The low-voltage winding carries the service current, so it is wound as aluminium or copper foil or strip. A uniform distribution of ampere-turns keeps stray loss and hot spots low and gives the winding a high short-circuit withstand capability.
The high-voltage winding is built as a multilayer cylinder with oil ducts between layers, insulated for primary voltages from 2.4 kV to 34.5 kV and for a basic impulse level of 30 kV to 150 kV.
The tank is filled with mineral oil or a natural ester such as FR3. Besides insulating the windings, the fluid carries heat from the active part to the tank walls and keeps moisture away from the paper insulation.
A mild steel or stainless steel tank with external radiators dissipates the heat by natural oil circulation and ambient air, the ONAN cooling that is standard for this family. A KNAN arrangement is available where the load profile requires it.
Primary connections are brought out through porcelain or polymer bushings sized for the system voltage. Cable or arrester connections are made on the primary side without opening the tank, so the sealed oil space is never exposed in service.
The tank is fitted with a mounting bracket and lifting provisions so the transformer can be hoisted and bolted directly to a pole cross-arm. No pad, vault or fenced compound is needed, which is what makes this family the standard choice for overhead distribution.
Two arrangements are built: a completely self-protected (CSP) unit with internal primary protection, or a conventional unit that relies on external cutouts and arresters. The choice follows the utility practice of the network the transformer is going into.
Off-circuit taps give plus or minus 2 x 2.5 percent above and below the rated voltage, so the secondary voltage can be trimmed on site to the actual primary level. Taps are changed with the unit de-energised.
The secondary leads are brought out to clearly marked terminals for the service connection. A stainless nameplate records the rated capacity, voltages, vector group Ii0 or Ii6, impedance and the standard the unit was tested to.
Every pole mounted transformer is tested before shipment against the applicable standards and the customer specification — from incoming raw material to the final routine test on the factory floor.
Quality starts with what comes through the gate. Tank steel, core laminations, winding conductor and insulating oil are checked against the approved specification for each batch, and supplier records are kept so that every component can be traced back to its heat number.
Progress checks are carried out at the winding, core stacking, tanking and oil-filling stages, so that every 25kVA single-phase pole mounted transformer is verified against its design before it reaches final assembly.
Each unit then goes through routine testing in accordance with IEEE / ANSI, IEC and CSA practice — insulation resistance, winding resistance, voltage ratio and polarity, no-load loss and current, load loss and impedance, applied and induced voltage withstand, and oil tightness and pressure testing. Efficiency is verified to DOE 2016 levels.
The finished transformer leaves the factory with a routine test report and a certificate of conformity, recording the measured values against the rated data on the nameplate.
25kVA Single Phase Pole Mounted Transformers are configured to the distribution practice of the project. Primary voltage, secondary voltage and vector group are selected first, then the protection and material options are added on top.
Primary windings can be built from 2.4 kV up to 34.5 kV, or to a customized primary voltage where the network requires it, and the secondary winding is wound to the project requirement. Vector group Ii0 or Ii6 is available, and the unit can be supplied for 50 Hz or 60 Hz operation.
The active part can be wound in aluminium or copper, on a core of grain-oriented electrical steel, and the tank can be supplied in mild steel or stainless steel with a customized finish. Insulation fluid is chosen as conventional mineral oil or as a natural ester such as FR3 where fire risk or environmental sensitivity calls for it.
Protection and mounting options cover the CSP or conventional arrangement, HV taps at plus or minus 2 x 2.5 percent, and the bracket and terminal layout needed for the pole hardware already in service on the line.
Every single-phase pole mounted transformer is packed, documented and shipped ready for pole installation.
Secure Packaging: Weather-resistant crating protects the tank, bushings and radiators against moisture, vibration and impact during transport and storage.
Oil-Tight Preparation: Units are shipped with the oil level and sealing checked after the routine tests, and the tank is sealed for the journey.
Reliable Transport: Road, rail or sea freight is arranged according to the project schedule and destination.
Complete Documentation: Routine test report, certificate of conformity, nameplate data, installation instructions and shipping documents travel with the unit.
Installation Support: Guidance on pole mounting, primary and secondary connections, earthing and energisation is available for smooth commissioning.
Impedance voltage is between 1.1 percent and 5.75 percent across the range, and the value for the ordered unit is recorded in the routine test report.
A pole mounted transformer is a distribution transformer designed to be mounted directly on a pole cross-arm, usually single phase, with overhead primary and secondary connections. It steps the line voltage down to the service voltage at the point where the customer is connected, so no ground-level enclosure is required.
Losses are controlled to the efficiency levels that apply to overhead distribution transformers in the destination market.
