350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise
Presenting the high-performance 350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise, a cutting-edge, eco-friendly power distribution solution ideal for indoor applications demanding superior safety and quiet operation. This three-phase dry-type transformer utilizes premium epoxy resin vacuum casting on high-conductivity copper windings and low-loss grain-oriented silicon steel cores, achieving outstanding energy efficiency (typically 98%+), minimal no-load/load losses, and exceptional partial discharge suppression (<10pC). With natural air (AN) cooling, Class F/H insulation, fire-retardant self-extinguishing properties, and robust short-circuit withstand, it offers maintenance-free reliability in harsh or sensitive environments. Fully compliant with IEC 60076-11, this compact unit steps down 6.6kV primary (with ±2×2.5% off-circuit taps) to 0.4kV secondary (Dyn11 vector group), supporting sustainable grids with overload capability and zero oil risks.
- Primary Voltage Ratings 6.6 kV (6600 V) delta or grounded wye
- Secondary Voltage Ratings 0.4 kV (400/230 V) wye
- H.V. Tap Range ± 2×2.5% HV taps or others
- Type Dry type transformer
- BIL 30/95kV
- Standards IEEE, ANSI, NEMA,IEC,GB
- Application office buildings, retail centers, schools, hospitals
- Power Rating 350kVA
- Certificate IEC 60076-11, IEC 60076-1, IEC 60076-3, UL 1561
- Cooling Method OA/OF
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise
Technical Specifications
Accessories
| Rated Power | 350 kVA | |
| Rating Primary Voltage | 2.4-35kV | |
| Secondary Voltage | 480/277V 400/230V 380/220V Customized |
|
| Frequency | 50/60Hz | |
| Vector Group | Dyn11,Yyn0,Dyn5 | |
| Winding Material | Aluminum/Copper | |
| Efficiency | As IEEE,Doe 2016,CAS Std or Customized | |
| Impedance Voltage | Nominal 2% or Customized 1.1-5.75% | |
| Altitude | ≤1,000m or Customized | |
| Enclosure material | 304 Stainless Steel | |
|
Insulation system |
Class F (155°C) or Class H (180°C) rise |
|
|
Winding materia |
Full high-conductivity copper (HV & LV) for maximum efficiency and lowest hot-spot temperatures |
|
| HV Bushing |
| LV Bushing |
| Tap changer connector |
| Lifting hook for complete transformer |
| Name plate |
Customization Optional
350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise
The 350kVA three-phase cast resin dry type transformer supports comprehensive customization to precisely match project voltage needs, acoustic limits, installation constraints, load profiles, and regional efficiency regulations. Primary voltage is centered on 6.6 kV (6600 V) in delta or grounded wye configuration, while secondary voltage can be configured as 400/230 V, 415/240 V, 480Y/277 V, or any custom low-voltage output. Vector groups include Dyn11 (standard), Dyn1, Yyn0, or special configurations for phase shift and harmonic mitigation. Full copper windings are standard for maximum efficiency, lowest hot-spot temperatures, and superior short-circuit strength; aluminum windings are available for cost-sensitive applications. Insulation system options are Class F (155°C) or Class H (180°C) using advanced cast-resin (epoxy) encapsulation for excellent resistance to moisture, dust, chemicals, and thermal cycling.
Enclosure choices include IP23 ventilated (indoor standard), IP54/IP55 totally enclosed (dust-tight/outdoor), or forced-air cooled (AF) for 133–150% overload capacity in high-ambient or confined spaces. Temperature rise can be specified as 100°C or 120°C. Additional features include forced-air cooling packages with fan controls, digital temperature monitoring with alarm/trip relays, surge arresters, electrostatic shielding for noise-sensitive locations, K-factor rating (K-4 to K-13) for harmonic-rich loads (data centers, EV charging, variable frequency drives), seismic bracing, ultra-low-noise execution (<50 dB with special core clamping and fan design), and special finishes for corrosive or cleanroom environments. All variants are fully validated to IEC 60076-11, CE marking, UL 1561 (if requested), local efficiency standards, and client specifications.
Packing and Shipping
350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise
Packaging the 350kVA Epoxy Resin Cast Dry Type Transformer focuses on protecting the vacuum-cast windings and core from transit stresses. The unit is anchored to a sturdy wooden pallet with rubber anti-vibration pads, corner protectors, and lifting eyes for safe maneuvering. Terminals, sensors, and exposed parts receive foam padding and rigid shields, while the assembly is wrapped in multi-layer moisture-barrier film and breathable covers. A robust, ISPM 15-treated wooden crate fully encloses it, reinforced with internal supports, desiccant bags, humidity indicators, and shock/tilt recorders to verify gentle handling and preserve the dry-type integrity.
Shipping options deliver secure, timely transport worldwide for this low-noise cast resin unit. Sea freight in 20ft/40ft containers provides economical global movement with secure bracing, averaging 20-50 days to ports. Air freight handles urgent deliveries in 5-10 days. Domestic/regional trucking uses enclosed trailers with weather shielding and secure fastenings for compliant overland transit. Full-value insurance safeguards the investment end-to-end.
Export paperwork includes invoices, packing lists, origin certificates, test reports, and IEC compliance docs for smooth customs. Sustainable practices use recyclable crates and optimized routes to cut emissions. Clients get real-time GPS tracking with alerts and dedicated logistics coordination.
Arrival services offer optional unpacking guidance, insulation checks, and eco-disposal of packaging to accelerate setup. Multi-unit orders enable consolidated loading and sequenced delivery. This rigorous process ensures flawless arrival, boosting SEO for "reliable low-noise dry type transformer shipping."
Domestic shipping uses enclosed trailers or flatbeds with secure blocking and tie-downs to minimize vibration. International shipments typically utilize 20ft/40ft containers (palletized and shrink-wrapped) or flat-rack loading, with professional lashing using chains and timber dunnage for sea and road stability. Upon arrival, detailed handling and installation manuals are provided, covering lifting procedures (via integrated lifting eyes), foundation placement with ventilation clearances, electrical connections, grounding, and pre-energization checks (insulation resistance, turns ratio, temperature sensor calibration).
Shipping options deliver secure, timely transport worldwide for this low-noise cast resin unit. Sea freight in 20ft/40ft containers provides economical global movement with secure bracing, averaging 20-50 days to ports. Air freight handles urgent deliveries in 5-10 days. Domestic/regional trucking uses enclosed trailers with weather shielding and secure fastenings for compliant overland transit. Full-value insurance safeguards the investment end-to-end.
Export paperwork includes invoices, packing lists, origin certificates, test reports, and IEC compliance docs for smooth customs. Sustainable practices use recyclable crates and optimized routes to cut emissions. Clients get real-time GPS tracking with alerts and dedicated logistics coordination.
Arrival services offer optional unpacking guidance, insulation checks, and eco-disposal of packaging to accelerate setup. Multi-unit orders enable consolidated loading and sequenced delivery. This rigorous process ensures flawless arrival, boosting SEO for "reliable low-noise dry type transformer shipping."
Domestic shipping uses enclosed trailers or flatbeds with secure blocking and tie-downs to minimize vibration. International shipments typically utilize 20ft/40ft containers (palletized and shrink-wrapped) or flat-rack loading, with professional lashing using chains and timber dunnage for sea and road stability. Upon arrival, detailed handling and installation manuals are provided, covering lifting procedures (via integrated lifting eyes), foundation placement with ventilation clearances, electrical connections, grounding, and pre-energization checks (insulation resistance, turns ratio, temperature sensor calibration).
32
32 years of industry experience
Manufacturer Test
350kVA Epoxy Resin Cast Dry Type Transformer 3 Phase 6.6kV/0.4kV Low Noise
Progress Test
Progress tests for the 350kVA three-phase cast resin dry type transformer are conducted at every critical manufacturing stage to ensure material quality and specification conformance. Core lamination stacking is inspected for precise alignment, clamp pressure uniformity, and inter-lamination insulation integrity to minimize no-load losses and audible noise. Winding fabrication progress verifies exact turn counts using automated counters, consistent conductor tension, correct transposition, and adequate insulation thickness between layers for balanced impedance and thermal distribution. After core-coil assembly, preliminary DC resistance, turns ratio, polarity, and inductance measurements are taken to confirm correct phasing, no shorted turns, and electrical symmetry before encapsulation. Cast resin encapsulation progress monitors resin mixing ratios, vacuum pressure levels, curing temperature profiles, and partial discharge testing during cure to ensure void-free insulation. Enclosure assembly checks verify fit-up, ventilation openings (if ventilated), grounding continuity, and surface preparation for paint adhesion. These incremental checks enable early identification and correction of nonconformities, ensuring the finished transformer meets efficiency, dielectric, and reliability targets.
Design Tests
All transformer will be test after finished the production, test items as below:
♦ Insulation Power Factor
♦ Winding Resistance
♦ Impulse Tests
♦ On load Loss Test
♦ No Load Loss Test
♦ Leak Test
♦ DC Insulation Resistance Test
♦ Transformer Turns Ratio/TTR (All Tap Voltages)
♦ Impedance Voltage & Load Loss (Rated Voltage)
♦ Excitation & No-Load Loss (Rated Voltage)
♦ Applied Voltage
♦ Insulation Resistance (Rated Voltage)
♦ Temperature Rise
Transformer Factory Acceptance Test
Factory acceptance testing (FAT) for the 350kVA three-phase cast resin dry type transformer strictly follows IEC 60076-11, IEEE C57.12.91, and UL 1561 protocols to confirm full compliance before shipment. Routine visual and mechanical inspections verify enclosure finish, weld quality (if applicable), nameplate data accuracy, accessory mounting, and terminal tightness. Winding resistance is measured across all tap positions at reference temperature to confirm conductor uniformity and match calculated loss values. Turns ratio (TTR) testing is performed on every tap to ensure ratio accuracy within 0.5% and correct vector group alignment. Polarity and phase relation checks confirm proper connection. Insulation resistance (megger at 2500–5000 V) evaluates winding-to-winding and winding-to-ground paths for multi-gigohm readings. Applied potential withstand test applies one-minute power-frequency voltage to HV and LV separately per insulation class without breakdown or excessive corona.
Routine Test - DC Insulation Resistance Test
Purpose of Testing
The purpose of DC insulation resistance testing is to measure the insulation resistance of a device by applying a DC voltage, thereby evaluating the health of the insulation material and the voltage withstand capability of the electrical device. This test helps detect potential insulation aging, moisture or damage, preventing electrical failures in the device.
Testing Equipment
Insulation resistance tester (e.g. Megger, Fluke, Hioki, Klein Tools, etc.)
Voltage source (usually 500V, 1000V, 2500V, or customized according to customer requirements)
Temperature and humidity meter (used to record the ambient temperature and humidity during the test to ensure that the test conditions meet the standard requirements.)
Voltage source (usually 500V, 1000V, 2500V, or customized according to customer requirements)
Temperature and humidity meter (used to record the ambient temperature and humidity during the test to ensure that the test conditions meet the standard requirements.)
Pre-Test Preparation
Make sure the device is properly grounded and fully discharged to prevent residual charge in the device from affecting the test results.
Perform the test under suitable environmental conditions. It is recommended to have a relative humidity below 75%, no rain, and a temperature range of 20-30°C to avoid moisture or temperature fluctuations affecting the test results.
Perform the test under suitable environmental conditions. It is recommended to have a relative humidity below 75%, no rain, and a temperature range of 20-30°C to avoid moisture or temperature fluctuations affecting the test results.
Test Progress
Connect the Test Instrument:
Connect an insulation resistance tester to the high voltage terminal of the device under test and to ground.
Apply Test Voltage:
Select an appropriate test voltage based on the rated voltage of the equipment .
Connect an insulation resistance tester to the high voltage terminal of the device under test and to ground.
Apply Test Voltage:
Select an appropriate test voltage based on the rated voltage of the equipment .
Measure and Record
Start the test and record the following parameters:
Insulation resistance value (MΩ)
Applied voltage
Ambient temperature and humidity during testing
Insulation resistance value (MΩ)
Applied voltage
Ambient temperature and humidity during testing
Temperature Correction
The measured insulation resistance values are corrected to a reference temperature (usually 20°C) for accurate evaluation.
Repeat Testing (if necessary)
Measure different windings (high voltage, medium voltage, low voltage) or each bushing separately, and conduct comparative analysis to ensure the insulation status of all parts.
Evaluation Criteria (Reference)
nsulation resistance ≥ 1000 MΩ (excellent)
500 MΩ ≤ Insulation resistance < 1000 MΩ (good)
100 MΩ ≤ Insulation resistance < 500 MΩ
Insulation resistance < 100 MΩ
500 MΩ ≤ Insulation resistance < 1000 MΩ (good)
100 MΩ ≤ Insulation resistance < 500 MΩ
Insulation resistance < 100 MΩ
Test standard
IEEE C57.12.01 & IEEE C57.12.91 (Dry-Type)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
Widely deployed in commercial office buildings, retail centers, schools, hospitals, and high-rise residential towers for safe indoor step-down from 10 kV medium-voltage to 400/230 V low-voltage distribution. Perfect for fire-sensitive or space-constrained locations where oil-filled transformers are restricted by building codes, insurance requirements, or environmental regulations.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
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