7MVA 22kV to 6.6kV Power Transformer ONAN Cooling Low Loss
The 6kV Three-Phase Oil-Immersed Power Transformer is designed for stable and efficient voltage conversion in industrial and commercial power distribution systems. With a durable oil-immersed insulation structure and high-quality copper windings, it offers excellent thermal performance, strong dielectric strength, and reliable operation under varying load conditions. Its compact design, robust core materials, and advanced cooling system ensure low losses, reduced noise, and long service life. This 6kV transformer is suitable for factories, mining sites, distribution stations, and utility networks requiring consistent and safe electrical power supply. Engineered to meet international standards, it provides dependable performance and high efficiency across diverse low-to-medium voltage applications.
- Primary Voltage Ratings 22kV, 6.6kV or others
- Secondary Voltage Ratings 13.8kV 6kV 10kV or others
- H.V. Tap Range ±8×1.25% or others
- Type Oil-immersed power transformer
- BIL 22kV, 6.6kV
- Standards IEEE, ANSI, NEMA, IEC, CE
- Application mining operations, oil & gas facilities
- Power Rating 7MVA
- Certificate UL, CESI, IEEE
- Cooling Method ONAN/ONAF
- Oil Mineral Oil or FR3
- Opeartion Step Down & Step Up
Technical Specifications
Customization Optional
Packing and Shipping
Manufacturer Test
Routine Testing
Application
Technical Specifications
7MVA 22kV to 6.6kV Power Transformer ONAN Cooling Low Loss
Technical Specifications
Accessories
| Rated Power | 7MVA | |
| Rating Primary Voltage | 6.6kV, 22kV | |
| Secondary Voltage |
6.6kV 10kV 13.8kV 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 | |
| Color | ANSI 70 Light gray/Munsell 7GY3.29/1.5 or customized, etc | |
| Tank material | Mild Steel, 304 Stainless Steel | |
| HV Bushing |
| LV Bushing |
| Tap changer |
| Oil level gauge |
| Oil temperature indicator |
| Pressure relief device |
| Pressure vacuum gauge |
| Lifting hook for complete transformer |
| Name plate |
| Radiators |
| Oil upper filtering valve |
| Oil drain valve with 3/8" sampler |
Customization Optional
7MVA 22kV to 6.6kV Power Transformer ONAN Cooling Low Loss
The 7MVA 22kV/6.6kV Power Transformer offers comprehensive customisation to perfectly align with specific project requirements and enhance performance in diverse medium-voltage applications. Customers can choose between high-conductivity copper or aluminium windings to balance cost and efficiency, with options for enhanced insulation classes (up to Class F or H) for operation in extreme temperatures ranging from -40°C to 55°C. Voltage tapping configurations include off-circuit or on-load tap changers (±5% to ±10% in 2.5% steps) for precise voltage regulation under fluctuating loads. Cooling enhancements such as forced air (ONAF) upgrades or corrugated fins increase capacity by up to 30% for high-ambient installations. Additional protective features like Buchholz relays, pressure relief devices, and fibre-optic temperature monitoring enable advanced fault detection and integration with SCADA systems, ensuring optimal reliability and remote management for modern smart grids.
Further personalization includes vector group selections (Dyn11, YNd1, or custom) for seamless parallel operation and harmonic mitigation in non-linear load environments. Tank designs can be specified as conservator-type or fully sealed bellows for maintenance-free operation in polluted areas. Accessories such as HV/LV cable boxes, surge arresters, neutral grounding resistors, and digital smart sensors for oil quality and dissolved gas analysis (DGA) provide tailored protection and predictive maintenance capabilities. Special paint finishes for coastal or corrosive environments, along with noise-reducing enclosures below 65dB, make this low-loss ONAN transformer highly adaptable. These bespoke options ensure the transformer meets unique site constraints while maximizing energy efficiency and longevity, positioning it as a top choice in searches for "customizable high-efficiency medium-voltage power transformers."
Packing and Shipping
7MVA 22kV to 6.6kV Power Transformer ONAN Cooling Low Loss
To guarantee safe delivery of the 7MVA 22kV/6.6kV Power Transformer, we employ heavy-duty export-grade packaging designed to withstand long-distance transport and harsh conditions. The transformer is securely mounted on reinforced steel skids with shock-absorbing pads to minimize vibration damage. A robust wooden crate or open-top steel frame, treated per ISPM 15 standards, encases the unit, while protective coverings shield bushings, radiators, and accessories from dust and moisture. Desiccant bags and nitrogen blanketing inside the tank prevent internal condensation during transit. Impact recorders and tilt indicators are affixed to monitor handling, enabling immediate claims if mishandling occurs.
We offer versatile global shipping solutions tailored to project timelines and budgets for this medium-voltage power transformer. Sea freight in dedicated 40ft high-cube containers provides cost-effective delivery for international orders, with full lashing and securing per IMO regulations for oil-filled equipment. Transit times range from 25-50 days, depending on destination ports, including options for FCL or LCL consolidation on bulk orders. Air freight is available for urgent spares or smaller components, achieving delivery in 5-10 days. Overland transport utilizes specialized low-bed trailers with escort services for oversized loads, ensuring compliance with road weight and height restrictions.
All shipments include detailed documentation packages to streamline customs clearance, featuring commercial invoices, packing lists, certificates of origin, and factory test reports optimized for "low-loss power transformer export logistics." Hazardous material declarations for mineral oil are prepared in advance, with UN-approved labeling. Eco-conscious practices incorporate recyclable crating materials and optimized routing to reduce carbon emissions. Real-time GPS tracking and dedicated logistics coordinators provide updates from factory loading to site unloading, maintaining transparency throughout the journey.
Upon arrival, our team supports smooth unpacking and positioning with detailed guidelines and optional supervision services. Debris removal and recycling of packing materials are arranged to minimize site impact. For multi-unit projects, phased deliveries synchronize with installation schedules, reducing storage needs. This end-to-end packing and shipping service underscores our commitment to delivering your 7MVA ONAN cooling transformer in perfect condition, enhancing satisfaction in searches for "reliable heavy power transformer transportation."
We offer versatile global shipping solutions tailored to project timelines and budgets for this medium-voltage power transformer. Sea freight in dedicated 40ft high-cube containers provides cost-effective delivery for international orders, with full lashing and securing per IMO regulations for oil-filled equipment. Transit times range from 25-50 days, depending on destination ports, including options for FCL or LCL consolidation on bulk orders. Air freight is available for urgent spares or smaller components, achieving delivery in 5-10 days. Overland transport utilizes specialized low-bed trailers with escort services for oversized loads, ensuring compliance with road weight and height restrictions.
All shipments include detailed documentation packages to streamline customs clearance, featuring commercial invoices, packing lists, certificates of origin, and factory test reports optimized for "low-loss power transformer export logistics." Hazardous material declarations for mineral oil are prepared in advance, with UN-approved labeling. Eco-conscious practices incorporate recyclable crating materials and optimized routing to reduce carbon emissions. Real-time GPS tracking and dedicated logistics coordinators provide updates from factory loading to site unloading, maintaining transparency throughout the journey.
Upon arrival, our team supports smooth unpacking and positioning with detailed guidelines and optional supervision services. Debris removal and recycling of packing materials are arranged to minimize site impact. For multi-unit projects, phased deliveries synchronize with installation schedules, reducing storage needs. This end-to-end packing and shipping service underscores our commitment to delivering your 7MVA ONAN cooling transformer in perfect condition, enhancing satisfaction in searches for "reliable heavy power transformer transportation."
32
32 years of industry experience
Manufacturer Test
7MVA 22kV to 6.6kV Power Transformer ONAN Cooling Low Loss
Progress Test
In-process quality checks for the 7MVA 22kV/6.6kV transformer begin with core stacking verification, measuring core loss at rated flux density to confirm low-loss silicon steel performance below specified watts/kg. Winding resistance and turns ratio tests ensure precise copper coil fabrication and uniform voltage distribution. Tank welding integrity is validated through dye penetrant and radiographic inspections, followed by vacuum leak tests at 0.01 mbar. Partial oil filling allows early dielectric tests between windings and ground, targeting insulation resistance above 2GΩ. These staged evaluations, supported by digital traceability records, guarantee progressive compliance with high-efficiency standards during manufacturing.
Design Tests
All transformer will be tested after finishing the production, test items as follows:
♦ Insulation Power Factor
♦ Ratio, Polarity, and Phase Relation
♦ 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)
♦ Polarity, 1-Ph / Phase Relation, 3-Ph (Rated Voltage)
♦ Excitation & No-Load Loss (Rated Voltage)
♦ Applied Voltage
♦ Induced Voltage
♦ Lightning Impulse
♦ Insulation Resistance (Rated Voltage)
♦ Temperature Rise
♦ Dielectric Withstand (Hipot)
Transformer Factory Acceptance Test
Comprehensive FAT continues with temperature rise testing under rated load, monitoring oil and winding hotspots to stay within 60K/65K limits for ONAN cooling. Sound level measurement in semi-anechoic conditions confirms acoustic performance below the specified dB(A). Chopped impulse tests on both HV and LV windings simulate lightning surges, verifying BIL ratings. The operation cycling of tap changers and accessories demonstrates mechanical endurance. Zero-sequence impedance and auxiliary circuit checks complete the protocol, delivering a fully validated low-loss power transformer ready for shipment.
Routine Test - Applied Voltage
Purpose of Testing
The purpose of testing the applied voltage is to verify the insulation strength of the transformer by applying a voltage higher than its normal operating level, ensuring it can withstand potential electrical stresses. This test helps identify any weaknesses or defects in the insulation system before the transformer is put into service.
Testing Equipment
Test equipment: High voltage tester (e.g. TTR, Hipot, etc.)
Voltage source: usually 1 kV, 5 kV, 10 kV, or customized according to customer needs
Temperature and humidity meter: used to record environmental conditions
Voltage source: usually 1 kV, 5 kV, 10 kV, or customized according to customer needs
Temperature and humidity meter: used to record environmental conditions
Pre-Test Preparation
Disconnect the device from the power supply and make sure it is properly grounded and discharged.
Check the connection terminals and wiring to ensure that they are not loose or contaminated.
Test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C).
Check the connection terminals and wiring to ensure that they are not loose or contaminated.
Test under suitable environmental conditions: relative humidity below 75% and no rain (recommended temperature: 20-30°C).
Test Progress
Connect the Test Instrument:
Properly connect the test equipment to the bushings or terminals of the device under test and ensure that all connection points are properly grounded.
Selecting the test voltage:
Select the appropriate applied voltage based on the rated voltage of the equipment.
Properly connect the test equipment to the bushings or terminals of the device under test and ensure that all connection points are properly grounded.
Selecting the test voltage:
Select the appropriate applied voltage based on the rated voltage of the equipment.
Measure and Record
Start the test and record the following parameters:
Measuring leakage current
Applied voltage
Current stability
Any possible voltage fluctuations
Measuring leakage current
Applied voltage
Current stability
Any possible voltage fluctuations
Temperature Correction
If necessary, the measured data is temperature corrected to ensure that it corresponds to standard temperature conditions (usually 20°C).
Repeat Testing (if necessary)
Multiple tests were conducted on different windings (high voltage, medium voltage, low voltage) and bushings, and comparative analysis was performed.
Evaluation Criteria (Reference)
The test was normal and the equipment performed well (qualified)
The current value exceeded the allowable range and the equipment needs to be inspected or maintained (pending repair)
There was a serious fault or instability and the equipment could not continue to operate (unqualified)
The current value exceeded the allowable range and the equipment needs to be inspected or maintained (pending repair)
There was a serious fault or instability and the equipment could not continue to operate (unqualified)
*These comprehensive tests ensure that each transformer meets performance standards and operates
reliably under various conditions.
Application
Perfect for heavy industrial plants, this 7MVA transformer reliably supplies medium-voltage power to steel mills and chemical facilities with minimal energy losses.
Technical Advantages
● 30+ years of manufacturing experience
● ISO and UL certified production
● Customized cable and transformer solutions
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What is a Transformer?A transformer is an electrical device used to change the voltage of alternating current (AC). It works on the principle of electromagnetic induction, converting high-voltage current into low-voltage current or low-voltage current into high-voltage current. Transformers are widely used in power transmission, distribution systems, and various electronic devices.
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What are the main uses of a transformer?The main use of a transformer is voltage conversion. Transformers are used in power transmission systems to help transfer electricity from power plants to consumers. In addition, transformers are also used in electronic devices such as chargers, televisions, power adapters, etc., to adjust the voltage to meet the requirements of different devices.
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Do you have UL listed?Yes, our transformer has UL listed. We have exported to America many pad mounted transformer,substation transformer and HV.
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