The 50kVA Three-Phase Fully Sealed Oil-Immersed Transformer is designed for distribution networks where maintenance access is limited and environmental exposure is high (humidity, dust, salt spray). Unlike conservator-type units, the sealed design prevents dielectric strength degradation caused by oil oxidation and moisture ingress.
Competitive Positioning: S11 Sealed vs Alternatives
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Feature
|
S11 Sealed (This Model)
|
S9 Open Type
|
Low-cost Aluminum Winding
|
|
Core material
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Hi-B grain-oriented silicon steel
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Conventional silicon steel
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Lower grade steel
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|
Winding conductor
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Oxygen-free copper
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Copper
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Aluminum
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Oil maintenance interval
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None (sealed)
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3–5 years
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3–5 years
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|
No-load loss (50kVA)
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0.13 kW
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0.18 kW
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≥0.20 kW
|
|
Typical lifespan
|
25–30 years
|
15–20 years
|
10–15 years
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Total Cost of Ownership Comparison (10 years, 50kVA)
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Cost component
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Sealed S11
|
Conventional open type
|
|
Initial purchase
|
$2,800
|
$2,400
|
|
Energy loss (10 yrs @ $0.12/kWh)
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$1,366
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$1,892
|
|
Oil testing/filtering (10 yrs)
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$0
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$800
|
|
Downtime risk cost
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Low
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Medium
|
|
10-year TCO
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~$4,166
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~$5,092
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50kVA Three-Phase Fully Sealed Oil-Immersed Transformer Savings: Approximately 18% lower TCO over 10 years.
Technical Parameters
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Rated capacity
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50 kVA
|
|
Voltage ratio
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10(6/11/20) / 0.4 kV
|
|
Tap range
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±2×2.5% (HV side)
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|
Frequency
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50 Hz
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|
No-load loss (guaranteed)
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0.13 kW
|
|
Load loss @75°C
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0.87 kW
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|
Impedance voltage
|
4%
|
|
No-load current
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1.8%
|
|
Total weight
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420 kg (oil: ~90 kg)
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Oil type
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Mineral oil (IEC60296)
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Temperature rise limit
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60K winding / 55K oil
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|
Cooling type
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ONAN
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Installation & Transport Requirements
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Minimum clearances: 600mm from walls (ventilation)
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Foundation: Level concrete pad, oil containment pit recommended
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Lifting: 4-point top lifting lugs (max lifting angle 30°)
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Transport: Standard 20ft container fits 1 unit + accessories
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Oil filling: Factory-filled, ready for connection
Environmental Ratings
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Condition
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Specification
|
|
Ambient temperature
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-25°C to +40°C
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|
Altitude
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≤1000m (derating above)
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|
Humidity
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≤95% non-condensing
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|
Enclosure protection
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IP54 (tank), IP00 (terminals)
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|
Sealing pressure test
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30 kPa positive, 24h no drop
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Core Engineering Differences
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Magnetic circuit: Step-lap core joints reduce magnetizing current by 12% compared to butt-lap designs used in standard S11 units.
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Winding structure: Layer-wound LV and HV with interlayer insulation paper, not randomly wound. This improves short-circuit withstand by distributing electromagnetic forces evenly.
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Sealing method: Welded tank body with bolted cover + oil-resistant NBR gasket. No weld porosity acceptance. Factory leak test at 0.05 MPa helium detection.
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Bushing type: Porcelain or epoxy resin (optional). Creepage distance: HV ≥ 240mm, LV ≥ 150mm (pollution class III).
Quality Verification Points
Instead of a generic test list, here are specific pass/fail criteria used in production:
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Partial discharge: ≤10pC at 1.3 × rated voltage (background noise ≤3pC)
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No-load loss tolerance: +0% / -10% of guaranteed value (IEC allows +15%)
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Sealing: 0.03 MPa compressed air submerged test – no bubbles for 30 seconds
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Lightning impulse (type test only): Full wave 75kV, chopped wave 85kV (for 10kV class)
Batch sample type tests available upon request at accredited labs (KEMA/CEPRI).
Application Decision Guide: When to Specify Fully Sealed
Choose fully sealed design when:
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Site has no regular maintenance staff (unattended substations)
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Ambient humidity exceeds 80% for >6 months/year
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Transformer is located in coastal or desert environment
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Oil disposal/replacement is logistically difficult
Choose conservator-type design when:
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Budget is extremely limited (saving ~15% upfront)
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Site has trained maintenance personnel
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Transformer is installed indoors with climate control
Warranty & Support Summary
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Warranty period: 12 months (manufacturing defects)
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Extended coverage: Additional 12 months available (invoiced separately)
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Technical documentation: Provided within 48 hours of shipment
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Remote support: Email/WeChat/WhatsApp with 24-hour response (excluding weekends)
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Field service: Available but quoted per trip (typically $1,500–3,000 plus travel)
FAQ
Q: What is the actual oil volume for shipping customs declaration?
A: Approximately 90 kg of mineral oil (K125X). HS code for transformer: 8504.22. Oil separate declaration not required if factory-filled.
Q: Can I mount this transformer on a pole?
A: No. 420kg total weight exceeds standard pole-mounted limits (typically ≤200kg). Pad-mounted or platform installation only.
Q: Do you provide a CAD drawing for substation layout?
A: Yes. 2D DWG and 3D STEP files available upon request after NDA or order confirmation.
Q: What is the expected lifespan before core insulation paper replacement?
A: Under rated load and ambient conditions, insulation paper retains >80% tensile strength for 25+ years (based on Arrhenius aging model with 6°C average hotspot margin).
Q: Is this transformer compliant with DOE 2016 efficiency standards (US)?
A: No. US DOE standards require 60Hz and specific loss limits. This is an IEC 50Hz unit. For US projects, request custom design.
Other available ratings (same S11 sealed series)
|
Model
|
Capacity (kVA)
|
No-load loss (kW)
|
Weight (kg)
|
|
S11-M-80/10
|
80
|
0.18
|
540
|
|
S11-M-100/10
|
100
|
0.20
|
605
|
|
S11-M-160/10
|
160
|
0.27
|
790
|
|
S11-M-250/10
|
250
|
0.40
|
1100
|
With a fully sealed oil system, high-permeability silicon steel core, and controlled manufacturing process, SGOB delivers a distribution transformer platform optimized for long-term grid stability. The SGOB 50kVA Three-Phase Fully Sealed Oil-Immersed Transformer ensures consistent performance, reduced maintenance dependency, and reliable operation in modern industrial and utility power systems.
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