HUARUI 
Dry Type isolation Transformer
A dry-type isolation transformer is a safety power supply device in which the input and output windings are completely electrically isolated, featuring air cooling and solid insulation as core technologies, and combining safety protection and interference suppression functions. It is widely used in power transmission and distribution locations that require safety isolation and clean power, such as high-speed railways, subways, high-rise buildings, airports, stations, hospitals, industrial and mining enterprises, CNC machine tools, and data centers.
Can be designed as 1:1 isolation for equal voltage, or step-up/step-down transformation as needed to meet different load voltage requirements while improving power supply imbalance issues.
Uses solid insulation materials such as epoxy resin casting or NOMEX paper, completely avoiding the use of flammable insulating oil, eliminating leakage and fire hazards, and producing no toxic smoke during operation, complying with fire protection and environmental requirements. Meanwhile, the input and output windings are completely electrically isolated, effectively preventing electric shock risks and ensuring personal safety.
Adopts a vacuum-cast solid insulation structure with high dielectric strength of the insulating material. There is no liquid medium between windings or between windings and the core, eliminating the risk of insulation failure caused by oil leakage. The primary and secondary windings feature extremely high insulation withstand voltage levels, ensuring the reliability of electrical isolation.
Eliminates the need for regular maintenance work such as oil sampling, oil filtration, and oil regeneration. The windings and core are completely encapsulated by solid insulation materials, isolating them from external dust and moisture. There is no need to replace the insulating medium during operation, significantly reducing operation and maintenance costs and workload.
Utilizes Air Natural (AN) or Air Forced (AF) cooling, requiring no auxiliary components such as radiators or oil conservators. The simple structure adapts to various installation environments.
Solid insulation materials age slowly under normal operating conditions, maintaining stable performance throughout their service life. The overall design life can reach 20-30 years, ensuring reliable long-term operation.
|
Parameter |
Specification |
|
Rated Capacity |
30kVA ~ 5000kVA (customization supported) |
|
High Voltage Rating |
6 ~ 10kV (customizable voltage levels) |
|
Low Voltage Rating |
400V (customizable as required) |
|
Cooling Method |
Air Natural (AN), Air Forced (AF) |
|
Insulation Class |
Class F (155℃) |
|
Impedance Voltage |
4 ~ 10% (depending on capacity and voltage level) |
|
Losses Compliant |
GB/T 19212.5-2025, UL, CSA, IEC, DOE2016, IEEE, ANSI, EN60076, etc.; low-loss optimization available |
|
Connection Group |
Dyn11, Yyn0, YNd11, Yy0, etc. (optional) |
|
Number of Phases |
Three-phase |
|
Rated Frequency |
50Hz / 60Hz |
|
Protection Level |
IP20 ~ IP65 |
|
Temperature Rise Limit |
Winding maximum temperature rise ≤ 100K |
|
Ambient Temperature |
Maximum: +40℃; Minimum: Indoor -5℃, Outdoor -25℃ (typically requires special design or enclosure) |
Core
Made of high-permeability grain-oriented silicon steel sheets laminated together to form the main magnetic circuit. Stepped lap or mitered joint processes effectively reduce eddy current losses and hysteresis losses, improving equipment operation efficiency. The core surface is coated with anti-rust insulating varnish, and the grounding plate is reliably led out.
Primary/Secondary Windings
Wound with high-quality copper or aluminum conductors (foil), divided into primary winding (input side) and secondary winding (output side). Solid insulation structure is adopted, using epoxy resin vacuum casting (encapsulated type) or NOMEX paper/glass fiber (non-encapsulated type). Enhanced insulation layer is provided between primary and secondary windings to ensure complete electrical isolation.
Input/Output Terminal Leads
Using copper busbars, copper terminals, or cable junction boxes to achieve internal and external electrical connections. Input side and output side terminals are clearly marked and distinguished. Closed busway interfaces, cable plug-in connectors, or terminal boxes can be selected according to customer requirements.
Cooling Components
Including cooling fans (axial or centrifugal fans), air deflectors, etc. Cooling methods AN (Air Natural) or AF (Air Forced) are adapted according to power specifications to ensure temperature rise is controlled within specified limits.
Protective Enclosure (Optional)
Made of stainless steel, aluminum alloy, or galvanized steel sheet, providing different protection levels from IP20 to IP65. The enclosure is equipped with ventilation louvers, dust filters, and access doors to adapt to different installation environment requirements.
Shielding Layer (Optional)
An electrostatic shielding layer made of copper foil or aluminum foil is provided between primary and secondary windings and reliably grounded, effectively suppressing common-mode interference and high-frequency noise, improving power quality.
Insulation Support Components
Including insulating pads, insulating cylinders, and insulating barriers, made of DMC/SMC or epoxy glass cloth board materials, fixing the winding ends and ensuring that electrical clearances and creepage distances meet isolation requirements.
Base and Lifting Components
Welded from channel steel or I-beam, providing overall support for the transformer. The base is equipped with lifting rings, grounding bolts, and fixing holes, facilitating transportation, installation, positioning, and grounding connection.
1. Core Product Advantages
① Excellent Safety and Environmental Protection: Completely oil-free design eliminates the risk of oil leakage and fire hazards, and no toxic smoke is produced during operation.
② Flexible Voltage Transformation: Can be designed as 1:1 isolation for equal voltage, or step-up/step-down transformation as needed to meet different load voltage requirements while improving power supply imbalance issues.
③ Maintenance-Free Operation: Eliminates the need for regular maintenance work such as oil sampling, oil filtration, and oil regeneration.
④ Strong Environmental Adaptability: Protection levels (IP20 to IP65) and climate/environmental classes (C2/C3, E2/E3) can be selected according to the application scenario. With the addition of a protective enclosure, it can operate reliably outdoors or in highly polluted environments, adapting to special environmental requirements such as high altitude, salt spray, and humidity.
2. Service Life
The standard design life of a dry-type isolation transformer is typically 20 to 30 years, depending on the insulation class (Class F or Class H). With high-quality manufacturing processes and reasonable operating conditions, it can reach over 30 years. Its service life is primarily affected by operating temperature, insulation quality, overvoltage surges, and environmental factors. For every 8 to 10℃ the temperature exceeds the rated limit, the service life is approximately halved. Sustained overvoltages accelerate electrical aging and damage turn-to-turn insulation. Harsh environments such as high temperature, humidity, dust, and corrosive gases also significantly reduce reliability.
1. Daily Maintenance
① Regular Dust Cleaning: Use a vacuum cleaner or dry compressed air to clean dust from windings and core surfaces every quarter to half a year to prevent dust accumulation that may lead to reduced heat dissipation and degraded insulation performance.
② Check Operating Parameters: Daily observe whether the three-phase winding temperatures displayed on the temperature controller are balanced and whether there is any abnormal rise. Listen for uniform and normal operating sounds. Address any abnormalities promptly.
③ Tighten Connection Components: Every six months, check whether the winding pressing devices, core clamps, inlet/outlet terminal connections, and grounding wires are loose. Tighten immediately to the specified torque if looseness is found.
④ Test Insulation Performance: Annually measure insulation resistance using a 2500V megger (insulation resistance between high voltage side and ground/low voltage side should be >300MΩ). Test insulation before commissioning if the transformer has been out of service for more than 72 hours to prevent moisture-related faults.
2. Safety Regulations
1. Power-Off Operation: Maintenance must be carried out only after all isolating switches on both the high-voltage and low-voltage sides are completely disconnected. Strictly follow the procedures of power cut, voltage verification, discharge, and grounding wire installation.
2. Voltage Verification and Grounding: Only after performing three-level voltage verification and reliable grounding can work begin. Hang a "Do Not Close" warning sign.
3. Residual Charge Release: After the transformer is powered off, residual charge must be fully discharged before maintenance can be carried out. Special attention should be paid to the capacitive energy storage effect of the isolation transformer windings.
1. Rail Transportation: Signal systems, communication systems, station lighting, and power supply systems in stations.
2. Medical Facilities: Hospital operating rooms, ICUs, medical imaging equipment (CT, MRI), and life support systems.
3. Data Centers: Server rooms, communication base stations, and cloud computing centers.
4. Industrial Manufacturing: CNC machine tools, automated production lines, and PLC control systems.
5. Building Facilities: High-rise buildings, airports, stations, and commercial complexes.
6. New Energy Sector: Photovoltaic inverters and energy storage systems.
7. Industrial and Mining Enterprises: Petroleum, chemical, mining, and other locations with high safety requirements.
1. Environmental Risks
1. Dust Contamination Risk: The winding surface of a dry-type isolation transformer is exposed or the cast body is in a high-dust environment for a long time. Dust accumulation will reduce heat dissipation efficiency and shorten creepage distance, which may cause surface flashover or intensified partial discharge.
2. Moisture and Condensation Risk: In a high-humidity environment for a long time or in places with large temperature differences between day and night, the surface of solid insulation easily absorbs moisture and forms condensation, resulting in a significant decrease in insulation resistance and a reduction in the partial discharge inception voltage, and in severe cases, surface flashover occurs.
3. High-Temperature Overheating Risk: When installed in poorly ventilated enclosed spaces, basements, or near heat sources, the ambient temperature exceeds the design reference value of 40℃, causing the winding temperature rise to exceed the standard, accelerating the thermal aging of insulation materials and significantly shortening the service life.
4. Noise and Vibration Impact: The magnetostriction of the iron core generates electromagnetic noise of 100Hz~400Hz, which may exceed the standard (e.g., ≤45~50dB at night) in quiet places such as residential areas, hospitals, and data centers, affecting people's work and rest.
5. Corrosive Gas/Salt Spray Risk: Corrosive gases or salt spray in chemical plants and coastal salt spray environments will corrode metal components such as core clamps, copper busbars, and enclosures, and may also corrode the cast body surface, reducing insulation reliability.
6. Overvoltage and Resonance Risk: The capacitance between windings is relatively large. Under the impact of switching overvoltage or lightning overvoltage, winding resonance may occur, leading to turn-to-turn insulation breakdown. At the same time, it is prone to ferroresonance with system capacitance.
2. Installation Restrictions
Dry-type isolation transformers shall be installed indoors in a well-ventilated, dry, clean environment free from corrosive media, with a safety clearance of at least 600mm reserved. For high-altitude or harsh environments, corresponding models or additional protective enclosures shall be selected.
This product supports full-dimensional personalized customization, enabling precise adaptation based on project operating conditions, environmental factors, industry standards, and customer requirements. The customization scope is as follows, with the main dimensions listed below:
|
Customization Dimensions |
Available Range |
|
Capacity & Voltage |
30 kVA ～ 5000KVA，6kv～10 kv |
|
Connection Group (Vector Group) |
Dyn11、Yyn0、YNd11、Yy0、ZNyn11 etc. |
|
Tap-Changer Type |
Off-circuit (No-load) (±2×2.5% or ±5%) / On-load (±8×1.25%, etc.) |
|
Cooling Method |
AN、AF |
|
Winding Material |
All-copper, all-aluminum, high-voltage aluminum / low-voltage copper, copper-aluminum composite, etc. |
|
Protection & Anti-Corrosion |
IP20 ～ IP65； |
|
Installation Environment |
Dry-type transformers shall be installed indoors in a well-ventilated, dry, clean environment, with ambient temperature -5℃ ~ +40℃, altitude ≤1000m, free from conductive dust, corrosive gases, and explosion hazards, with surrounding clearance reserved for heat dissipation and maintenance. |
|
Accessory Configuration |
Optional add-ons: intelligent temperature controller (winding temperature monitoring), partial discharge online monitoring, remote data transmission, over-temperature alarm/trip, automatic fan start/stop control, intelligent protective enclosure (with electromagnetic lock), temperature & humidity controller (anti-condensation), etc., adaptable to unattended intelligent power distribution systems and smart substations. |
|
Applicable Standards |
UL / EN 60076 / GB 1094 / IEC 60076 / ANSI C57.12 / CSA / DOE Energy Efficiency Levels |
|
Marking / Labeling |
Chinese/English or bilingual nameplate and warning labels |
