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WENFEI ELECTRICAL
WENFEI ELECTRICAL
EFFICIENT POWER DISTRIBUTION

Low-Voltage Transformers

Reliable power conversion for industrial, commercial and residential applications.

Precision-engineered low-voltage transformers delivering safe, efficient power distribution. Designed for 50/60Hz systems with voltage ratings from 380V to 690V, featuring copper or aluminum windings, epoxy resin encapsulation, and comprehensive protection against overload and short circuits.

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380-690V
Voltage Range
>98%
Efficiency
IP00-IP54
Protection Class
Low-Voltage Transformer Unit
Model -- LVT-1000/380

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Comprehensive range of low-voltage transformers for diverse power distribution requirements

Low-Voltage Transformers
HIGH EFFICIENCY

Low-Voltage Transformers

Precision-engineered low-voltage transformer designed for reliable power distribution in demanding industrial and commercial applications.

Capacity 50-2500 kVA
Voltage 380-690V
Efficiency > 98%
Insulation Class F / H
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Capacity
Calculator

Determine the optimal transformer capacity for your power distribution needs

Client
Testimonials

Real-world performance in critical applications

"We've installed 12 SCB13 transformers across our manufacturing facilities in Vietnam. Zero failures in 3 years of operation. The low-loss design has reduced our energy costs by 18%. Wenfei's technical support during installation was exceptional."
MN
Michael Nguyen
Facilities Manager, TechParts Vietnam
"Our data center required precise voltage regulation for sensitive server equipment. Wenfei's SCB10 series delivered exactly what we needed. The compact design saved valuable floor space, and the ultra-low noise level was crucial for our operations."
SA
Sarah Al-Mansoori
Infrastructure Director, CloudHub UAE
"Working in remote mining locations across Africa, reliability is everything. Wenfei transformers have operated flawlessly in harsh desert conditions for over 4 years. The moisture-proof design and robust construction are unmatched. Highly recommended."
JM
James Mwangi
Operations Manager, AfriMine Resources
"For our hospital expansion, we needed transformers that could handle critical life-support systems without any risk of failure. Wenfei's medical-grade transformers exceeded all expectations. The installation team was professional and thorough."
RC
Dr. Rosa Cardoso
Chief Engineer, Hospital São Paulo
10,000m²
Production Base
120+
Employees
ISO 9001
Certified
CE
EU Approved

Frequently Asked
Questions

Technical answers to common inquiries about low-voltage transformers

What is the difference between dry-type and cast resin transformers?
Dry-type transformers use air as the cooling medium and insulation system (Class F or H), suitable for general indoor applications. Cast resin transformers feature windings encapsulated in epoxy resin through vacuum pressure impregnation (VPI), providing superior moisture resistance, flame retardancy (self-extinguishing within 30 seconds), and partial discharge levels below 10pC. Cast resin types excel in harsh environments, coastal areas, and applications requiring enhanced safety (tunnels, hospitals, data centers).
How do I determine the correct transformer capacity for my facility?
Calculate total connected load in kW, convert to kVA using power factor (typically 0.8-0.9 for industrial, 0.9-0.95 for commercial), apply diversity/load factor (0.7-0.8), and add safety margin (1.15-1.25×). Formula: Transformer kVA = (Total kW ÷ PF) × Diversity Factor × Safety Factor. For facilities with motor loads, add 25-30% for inrush current. For future expansion, consider 20-30% additional capacity. Use our calculator above for quick estimates, or contact our engineers for detailed load analysis.
What are the advantages of copper vs aluminum windings?
Copper windings: Higher conductivity (60% better than aluminum), smaller physical size, better overload capacity, longer lifespan (30+ years), easier to repair. Aluminum windings: Lower cost (40-50% less), lighter weight (beneficial for rooftop installations), larger conductor cross-section required. For critical applications (data centers, medical facilities), copper is recommended. For cost-sensitive projects with adequate space (warehouses, general industrial), aluminum is acceptable. All Wenfei transformers use high-purity materials (99.95%+ copper or 99.7%+ aluminum) with proper connection technology to prevent oxidation.
What protection class (IP rating) do I need?
IP00: Open terminals, clean indoor electrical rooms only. IP20: Touch-protected terminals, standard indoor installations (most common). IP23: Drip-proof, suitable for areas with occasional moisture or condensation. IP44: Splash-proof, outdoor covered areas or high-humidity environments. IP54: Dust-protected and splash-proof, harsh industrial environments or outdoor enclosures. Higher IP ratings increase cost and reduce cooling efficiency. Most indoor commercial/industrial applications use IP20. Outdoor or coastal installations require minimum IP44. Consult local electrical codes for specific requirements.
How often do low-voltage transformers require maintenance?
Dry-type transformers are virtually maintenance-free. Recommended schedule: Monthly visual inspection (check for dust accumulation, unusual odors, loose connections). Quarterly thermographic scan (identify hot spots). Annual comprehensive inspection (tighten connections to specified torque, measure insulation resistance > 1000MΩ, verify cooling system operation, check for moisture ingress). Every 3 years: Partial discharge testing for cast resin types. Expected lifespan: 25-30 years with proper maintenance. Unlike oil-immersed transformers, no oil sampling or filtration required. Keep ventilation paths clear and ambient temperature below 40°C for optimal performance.
Can transformers handle harmonic loads from VFDs and LED lighting?
Standard transformers can handle up to 15% total harmonic distortion (THD). For facilities with significant non-linear loads (> 30% VFDs, switch-mode power supplies, LED lighting), specify K-factor rated transformers: K-4 (5-10% non-linear loads), K-13 (10-30% non-linear loads), K-20 (> 30% non-linear loads). K-rated transformers feature oversized neutrals (200% for K-13), increased conductor cross-sections, and enhanced cooling to handle harmonic heating. Alternatively, install harmonic filters upstream. Wenfei offers K-rated options for all standard capacities--specify requirements during quotation.
What certifications and standards do Wenfei transformers comply with?
All Wenfei low-voltage transformers comply with: IEC 60076 (power transformers general requirements), IEC 61558 (safety of power transformers), ISO 9001:2015 (quality management), CE marking (EU directives), RoHS (hazardous substance restriction). Optional certifications available: UL/cUL (North America), CCC (China compulsory), SASO (Saudi Arabia), SONCAP (Nigeria), EAC (Eurasian Customs Union). Each transformer undergoes factory testing per IEC standards: no-load loss, load loss, impedance voltage, temperature rise, insulation resistance, partial discharge (cast resin types), and impulse voltage withstand. Test reports provided with shipment.
What is the typical lead time and what does the warranty cover?
Lead time: Standard ratings (50-1000 kVA, 380-690V): 3-4 weeks. Large capacity (1000-3150 kVA): 4-6 weeks. Custom voltage/special requirements: 5-8 weeks. Express production available for urgent projects (contact sales). Warranty: 24 months from commissioning or 30 months from shipment date (whichever comes first). Coverage includes manufacturing defects, material failures, workmanship issues. Excludes damage from improper installation, operation beyond ratings, natural disasters, or unauthorized modifications. Extended warranty up to 5 years available. Spare parts guaranteed available for 15 years. Global service network provides technical support and on-site assistance.

The Definitive
Guide

Comprehensive technical reference for low-voltage transformers

What Are Low-Voltage Transformers?

Low-voltage transformers are electrical devices that convert alternating current (AC) from one voltage level to another within the low-voltage range (typically defined as ≤ 1000V AC per IEC standards). They step down medium-voltage distribution (6kV, 10kV, 35kV) to utilization voltages (220V, 380V, 400V, 415V, 480V, 690V) for industrial machinery, commercial buildings, and residential complexes. Unlike high-voltage power transformers, low-voltage units prioritize compact design, safety features, and installation flexibility for end-user applications.

Core Technologies & Construction

Core Design

High-grade cold-rolled grain-oriented (CRGO) silicon steel laminations, 0.23-0.35mm thickness, stacked and clamped with precision. Step-lap or mitred joints minimize magnetic flux leakage. Core loss typically 1.0-1.3 W/kg at 1.5T, 50/60Hz. Three-limb core for three-phase units, shell-type construction available for special applications requiring enhanced short-circuit strength.

Winding Technology

Concentric cylindrical windings (LV inside, HV outside) for optimal cooling and insulation. Copper or aluminum conductors with Class F (155°C) or Class H (180°C) insulation. Continuous disk winding for HV, layer winding for LV. Axial and radial spacers ensure proper oil/air flow. Transposition of parallel conductors minimizes circulating currents and eddy losses.

Insulation Systems

Dry-type: Nomex paper, polyester film, or glass fiber reinforced insulation. Cast resin: Epoxy resin vacuum pressure impregnation (VPI) encapsulates windings, providing mechanical strength and moisture resistance. Insulation withstand voltage: 2.5-3.0 kV AC for 1 minute (routine test). Partial discharge levels < 10 pC for cast resin types ensure long-term reliability.

Cooling Methods

AN (Air Natural): Free convection cooling for small units (< 500 kVA). AF (Air Forced): Fan-assisted cooling for medium/large units, improves capacity by 25-40%. Temperature rise: 100K (Class F) or 125K (Class H) above 40°C ambient. Thermostats and PT100 sensors monitor winding temperature. Optional IP54 enclosures for harsh environments.

Technical Specifications

Parameter Dry-Type Cast Resin Isolation Type
Capacity Range 50-2500 kVA 100-3150 kVA 10-1000 kVA
Voltage Ratings 380-690V 380-690V 220-480V
Efficiency > 98% > 98.5% > 98%
Impedance Voltage 4-6% 4-6% 3-5%
Insulation Class F (155°C) / H (180°C) F (155°C) / H (180°C) F (155°C)
Noise Level < 60 dB(A) < 55 dB(A) < 58 dB(A)
Protection Class IP00-IP54 IP20-IP44 IP20-IP44
Operating Temp -25°C to 40°C -25°C to 45°C -10°C to 40°C

Selection Guidelines

1. Load Analysis & Capacity Calculation

Identify all connected loads with their rated power (kW) and power factor. For motor loads, consider starting current (5-7× rated current for DOL, 2-3× for soft starters). Calculate: Transformer kVA = Σ(Load kW ÷ PF) × Diversity Factor × Safety Factor. Diversity factor accounts for non-simultaneous operation (0.7-0.9 typical). Safety factor provides headroom for future expansion (1.15-1.25). For cyclic loads (welders, cranes), use duty cycle to determine thermal equivalent load. Always round up to next standard rating.

Example: Factory with 500 kW motors (PF=0.85), 200 kW lighting (PF=0.95), 100 kW HVAC (PF=0.9). Diversity=0.8, Safety=1.2. Required kVA = [(500÷0.85 + 200÷0.95 + 100÷0.9) × 0.8 × 1.2] ≈ 850 kVA → Select 1000 kVA transformer.

2. Voltage System & Connection Configuration

Match transformer secondary voltage to load requirements: 380V (China, most Asia), 400V (Europe, Middle East), 415V (Australia, parts of Asia), 480V (North America industrial), 690V (heavy industrial motors). Specify connection group: Dyn11 (most common for LV distribution), Yyn0 (neutral earthing required), Dzn0 (zigzag for harmonic mitigation). For unbalanced loads, use four-wire system with properly sized neutral. Verify grounding system compatibility (TN-S, TN-C-S, TT, IT).

3. Environmental Conditions & Enclosure Selection

Assess installation environment: Indoor clean electrical room (IP20 adequate), Indoor dusty/humid (IP23-IP44), Outdoor covered (IP44 minimum), Outdoor exposed (IP54, weatherproof enclosure). For coastal/corrosive atmospheres, specify epoxy-coated enclosures and stainless steel hardware. Altitude > 1000m requires derating (1% per 100m). Ambient temperature > 40°C requires derating or enhanced cooling. Seismic zones may require special mounting provisions per IEC 60068-2-57.

4. Special Requirements & Options

K-factor rating for harmonic loads (VFDs, UPS, LED lighting): Specify K-4, K-13, or K-20 based on non-linear load percentage. Off-load tap changer (OLTC) for voltage adjustment: ±2.5%, ±5% typical. Temperature monitoring: PT100 RTDs embedded in windings, digital display, alarm contacts. Surge protection: Built-in MOV arresters for lightning/switching transients. Sound attenuation: Acoustic enclosures reduce noise by 10-15 dB(A). Parallel operation capability: Matching impedance and connection group for redundancy.

Installation Best Practices

  1. 1. Foundation & Mounting: Concrete pad or structural steel base, level within ±3mm per meter. Vibration isolation pads for noise-sensitive areas. Anchor bolts torqued to 80-120 Nm (M16). Maintain minimum clearances: 1.0m front (access), 0.5m rear/sides (ventilation), 2.5m overhead (arc flash). Floor load capacity must exceed transformer weight plus 50% (account for lifting equipment during maintenance).
  2. 2. Electrical Connections: Cable sizing per IEC 60364 or NEC: Ampacity ≥ 125% of transformer rated current, voltage drop < 3%. Use compression lugs, torque to manufacturer specification (typically 40-60 Nm for M12 terminals). Apply anti-oxidant compound on aluminum connections. Maintain phase sequence (L1-L2-L3 or A-B-C). Verify cable entry IP rating matches transformer enclosure. Install cable glands with proper strain relief.
  3. 3. Grounding & Bonding: Connect transformer frame and enclosure to facility ground grid using minimum 25mm² copper conductor (or per local code). Ground resistance < 1Ω for TN systems, < 4Ω for TT systems. Bond neutral point per system type: TN-S (separate PE), TN-C-S (combined PEN upstream, separate downstream), TT (neutral earthed at source and transformer). Install residual current devices (RCDs) if required by local regulations.
  4. 4. Protection Coordination: Primary protection: HRC fuses or circuit breaker rated 1.5-2.0× transformer FLC. Secondary protection: MCCB or ACB with adjustable thermal-magnetic trip, rated 1.25× transformer FLC. Set overcurrent protection to coordinate with upstream and downstream devices--use time-current curves. For motor loads, consider delayed tripping (10-30 seconds) to ride through starting inrush. Install differential protection for transformers > 1000 kVA.
  5. 5. Commissioning Tests: Visual inspection: Verify all connections tight, no shipping damage, cooling fans operational. Insulation resistance: Megger test at 1000V DC, reading > 1000 MΩ (new), > 100 MΩ (in-service). Turns ratio test: Verify within ±0.5% of nameplate. Polarity and phase sequence: Confirm correct connections. No-load test: Energize at rated voltage, measure no-load current (< 5% rated) and losses. Load test: Apply 25%, 50%, 75%, 100% load, verify voltage regulation and temperature rise. Protective device testing: Simulate fault conditions, verify trip settings.

Maintenance Schedule

Monthly
  • • Visual inspection for damage/overheating
  • • Check ventilation paths clear
  • • Verify cooling fans operational
  • • Monitor load levels and balance
  • • Record temperature readings
  • • Check for unusual noise/vibration
Quarterly
  • • Thermographic scan (infrared)
  • • Clean ventilation openings/filters
  • • Inspect electrical connections
  • • Verify protection device settings
  • • Check grounding system integrity
  • • Test temperature alarms/monitors
Annually
  • • Insulation resistance test (megger)
  • • Retorque all electrical connections
  • • Measure voltage regulation
  • • Power quality analysis (harmonics)
  • • Partial discharge test (cast resin)
  • • Comprehensive inspection report

Why Choose Wenfei?

Since 2019, Wenfei Electrical has specialized in low-voltage transformer design and manufacturing for critical power distribution applications. Our 10,000m² production facility in Liushi, Wenzhou--China's electrical equipment manufacturing hub--combines advanced CNC winding machines, vacuum pressure impregnation systems, and comprehensive testing laboratories. Every transformer undergoes 100% factory testing including no-load loss, load loss, impedance voltage, temperature rise, insulation resistance, and impulse voltage withstand tests per IEC 60076 standards.

Our engineering team provides application-specific design support, helping customers optimize transformer specifications for their load profiles, environmental conditions, and efficiency requirements. With ISO 9001:2015 certification, CE compliance, and a global service network spanning Southeast Asia, Middle East, Africa, and South America, Wenfei transformers deliver reliable performance in the world's most demanding power distribution environments--from high-rise buildings to heavy industrial facilities, data centers to renewable energy projects.

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Quote

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Direct Line
+86 577 6277 6688
Global Headquarters

Liushi Town, Wenzhou, Zhejiang, China