2025-06-19
three phase pad mounted distribution transformers are custom-made as per requirements.Daryuan Electric is a well-known manufacturer in China. They provide transformer specifications and sizes. Their transformer technology is mature and they are the original manufacturers for many large enterprises.
I. Core Electrical Parameters:
1.Rated Power (kVA): The apparent power output the transformer can deliver continuously at rated secondary voltage and frequency without exceeding temperature limits. Common Ratings: 25 kVA, 50 kVA, 75 kVA, 100 kVA, 167 kVA.
2.Primary Voltage (kV): The nominal line-to-line voltage applied to the HV winding. Common Values: 11 kV, 22 kV, 33 kV (Region/Utility specific).
3.Secondary Voltage (V): The nominal line-to-line voltage delivered by the LV winding under full load. Standard Value: 400V (415V) / 230V (240V) (3-phase 4-wire).
4.Insulation Level: Specified by Basic Insulation Level (BIL) and power frequency withstand voltage.
HV BIL: e.g., 95 kV for 11kV class, 170 kV for 33kV class.
LV BIL: e.g., 10 kV.
5.No-Load Loss (Iron Loss / Core Loss) (W): Power loss when energized at rated voltage and frequency with no load. Crucial for energy efficiency (24/7 loss). Minimized using high-grade CRGO steel.
6.Impedance Voltage (%Z): The percentage of primary voltage required to circulate full-load current in the secondary winding when short-circuited. Typical Range: 4% to 6% for distribution transformers. Affects fault current, voltage regulation, and parallel operation.
7.Load Loss (Copper Loss / I²R Loss) (W): Power loss due to load current flowing through the winding resistance at rated current and reference temperature (usually 75°C or 85°C). Minimized using appropriate conductor size/material.
8.Vector Group / Connection: The winding connection and phase displacement.
Common HV: Delta (D) - Provides a path for triplen harmonics.
Common LV: Star with neutral (y or Yyn) - Provides neutral for single-phase loads.
Common Group: Dyn11 (Delta HV / Star LV with 30° LV lagging HV). Dyn5 and Yzn are also used (esp. for lightning prone areas).
9.Frequency (Hz): 50 Hz or 60 Hz (Region specific).
10.Tapping Range (%): Allows adjustment of the HV turns to compensate for voltage variations on the primary network. Common: ± 2.5% or ± 5% in 2.5% steps (Off-Circuit Tap Changer - OCTC).
11.Total Loss (W): Sum of No-Load Loss and Load Loss.
12.Core Material: Grain-Oriented Electrical Steel (CRGO - Cold Rolled Grain Oriented) - Minimizes core loss and magnetizing current.
13.Insulation System: Oil-impregnated paper/cellulose for windings and barriers. Class A (105°C) insulation is standard.
14.Cooling Medium & Type: Mineral oil (or less commonly, ester fluid) cooled. Cooling type is typically ONAN (Oil Natural, Air Natural) - relies on natural convection.
15.Winding Material:
HV Winding: Copper or Aluminum.
LV Winding: Copper or Aluminum. Copper generally offers lower losses and better mechanical strength.
16.Tank Construction: Weatherproof, welded steel tank. Corrugated fins or radiators for heat dissipation. Often painted grey or utility-specific color.
17.Efficiency (%): (Output Power / Input Power) x 100% at specific loads (often 50% and 100% load). Governed by standards like IS 1180, DOE (USA), EU Ecodesign.
18.Voltage Regulation (%): The percentage change in secondary voltage from no-load to full-load (at constant primary voltage and power factor). Depends on %Z and load PF. Reg% ≈ (%R * cosφ) + (%X * sinφ).
19.Temperature Rise Limit (°C): Maximum allowable average winding temperature rise over ambient (usually 40°C or 50°C). Standard Limit: 65°C (for ONAN cooling, Class A insulation).
20.Sound Level (dB(A)): Audible noise level measured at a specified distance (e.g., 0.3m) under no-load conditions. Lower is better, especially in residential areas.
21.Weight:
Oil Weight (kg/liters): Significant portion of total weight.
Core & Coil Weight (kg):
Total Weight (kg): Ranges from ~300kg for 25kVA to ~1500kg for 167kVA.
22.Dimensions (L x W x H) (mm): Compact design is essential for pole mounting.
23.Mounting: Designed for vertical mounting on a utility pole using sturdy brackets.
24.Oil Volume (liters):
25.Terminations:
HV: Bushings (Porcelain or Polymer) for cable connection (e.g., 11kV/22kV class).
LV: Bushings (Porcelain or Polymer) or a terminal chamber/box for outgoing cables.
26.Conservator Tank (Yes/No): Small transformers (< ~100kVA) often use a "sealed tank" design without a conservator. Larger ones may have one.
27.Oil Level Indicator: Sight glass or gauge.
28.Pressure Relief Device: Rupture disc or valve to relieve excessive internal pressure.
