2025-08-14
The parameters of the three-phase pole type distribution transformer are provided below. We are a Chinese manufacturer and can provide you with the transformer model parameters you need for price consultation.
1. Rated Capacity (kVA):
Standard Ratings: 15, 25, 37.5, 50, 75, 100, 167 kVA (common); up to 500 kVA (less common on poles).
2. Voltage Ratings (V):
Primary (HV): Common: 11,000V (11kV), 13,200V (13.2kV), 13,800V (13.8kV), 22,000V (22kV), 33,000V (33kV). Range: Typically 6.35kV to 34.5kV.
Secondary (LV): Common: 120/240V (US Split-Phase), 208Y/120V, 240/120V (4-wire Delta), 480Y/277V, 400Y/231V (EU).
3. Vector Group / Connection:
Common HV: Delta (Δ) - Provides a path for third-harmonic currents. Label: `D` (e.g., Dyn).
Common LV: Wye (Y) - Provides a neutral point for grounding and single-phase loads. Label: `y` or `yn` (neutral brought out).
Most Common: Dyn11 (Delta HV, Wye LV with neutral, 30° phase shift - LV lags HV by 30°). Other possibilities: Dyn1, Yyn0, Yzn11 (zig-zag for ground fault current limiting).
4. Impedance (%Z):
Typical Range: 2% to 6% (Most common: 3-4%).
Purpose: Limits fault current; impacts voltage regulation. Higher %Z = lower fault current but worse regulation.
5. Voltage Regulation (%):
Typical: 2% to 5% (from no-load to full-load at rated power factor).
Depends on load, power factor, %Z, and transformer design.
6. No-Load Losses (Core Losses / Iron Losses):
Measured in Watts (W) at rated voltage and frequency.
Constant loss (independent of load). Key for energy efficiency (24/7 loss).
7. Load Losses (Copper Losses / Winding Losses):
Measured in Watts (W) at rated current and reference temperature (usually 75°C or 85°C).
Loss proportional to load current squared (I²R). Dominates at full load.
8. Efficiency (%):
Output Power / (Output Power + Total Losses) 100%.
Maximized near 35-50% load for most distribution transformers. Modern units prioritize low no-load loss.
9. Frequency (Hz): 50 Hz or 60 Hz.
10. Cooling Type:
ONAN: Oil Natural, Air Natural (Most common for pole-mounts). Oil circulates by convection; air cools tank.
ONAF: Oil Natural, Air Forced (Fans added for higher kVA ratings).
Coolant: Mineral oil (most common), Natural/Synthetic Ester fluid (less flammable, "less flammable" or "safety" transformers), Silicone fluid, FR3 (vegetable-based ester).
11. Enclosure / Tank:
Weatherproof, sealed tank (often with expansion space/diaphragm).
Materials: Corrugated steel (common for natural convection), finned steel, sometimes aluminum.
12. Bushings:
HV: Usually porcelain or polymer (3 or 4 - 3 phase + ground lug).
LV: Usually porcelain or polymer (4 - 3 phases + Neutral).
Often include test points (e.g., TPTs - Test Point Terminals) for metering/protection.
13. Taps (Tap Changer):
Type: Usually off-circuit (de-energized operation only).
Location: Typically on HV winding (± 2.5% or ± 5% in 2.5% steps - e.g., 2ANFC = Above Normal 2 taps, Below Normal 2 taps, Full Capacity).
14. Mounting:
Designed for mounting on a utility pole via bolts through integral lugs or brackets.
Weight: Critical for pole strength assessment. Ranges from ~250 kg (500 lbs) for 25kVA to over 1500 kg (3300 lbs) for 500kVA.
Dimensions (L x W x H): Varies significantly with kVA and design.
15. Insulation Class / Temperature Rise:
Standard System: A (105°C), B (130°C), F (155°C), H (180°C). Most common: 55°C or 65°C average winding temperature rise over ambient (usually 30°C or 40°C) using Class A insulation. Higher temp rise allows smaller core for same kVA rating.
16. Sound Level (dBA):
Measured at rated voltage and frequency under no-load conditions at a specified distance (e.g., 0.3m or 1m). Important for residential areas.
17. Lightning Impulse Withstand Level (BIL):
HV: Common: 95kV, 110kV, 125kV, 150kV (e.g., 110kV BIL for 15kV class).
LV: Common: 60kV, 75kV, 95kV.
Specifies ability to withstand voltage surges (like lightning).
18. Short-Circuit Withstand:
Ability to withstand mechanical/thermal stresses during a short-circuit for a specified duration (e.g., 2 seconds) without damage.
19. Lightning Arresters: Often mounted directly on transformer tank or structure.
20. Protective Devices:
Primary Fuse Cutout: Most common protection.
Internal/Secondary Fuses: Sometimes used on LV side.
Pressure Relief Device: Vents excess pressure safely.
21. Monitoring:
Temperature Gauge: Oil temperature indicator.
Smart Features: (Increasingly common) - Remote monitoring of load, voltage, temperature, fault detection (e.g., DGA sensors). Requires communication port (e.g., cellular modem).
22. Grounding:
Tank Ground: Robust connection to pole ground.
LV Neutral Ground: Solidly grounded (common) or impedance grounded.
Load Profile: Peak demand, diversity factor, future growth.
Voltage Profile: Source voltage, feeder length, required secondary voltage under load.
Fault Current: Coordination with upstream protection.
Environment: Ambient temperature, altitude (derating), corrosion (coastal), seismic zone.
Efficiency Standards: MEPS (Minimum Energy Performance Standards) like DOE 2016 (US), EU Ecodesign.
Safety: Less flammable fluids in high-risk areas.
> 75 kVA, 3-Phase, Pole Mounted Distribution Transformer
> HV: 13,200Y/7620 V (Delta connected internally)
> LV: 480Y/277 V
> Connection: Dyn11
> % Impedance: 4.0% @ 75kVA
> BIL: HV - 110kV, LV - 60kV
> Taps: HV 2ANFC (± 2x2.5%)
> No-Load Loss: 150 W
> Load Loss: 1150 W @ 75°C
> Cooling: ONAN
> Temperature Rise: 65°C
> Fluid: Mineral Oil
> Weight: ~ 600 kg
> Standards: IEEE C57.12.00, C57.12.20
