Dry Type Encapsulated Power Distribution Transformer Sizes, Applications and Maintenance

Transformers are the “traffic cops” regulating the flow of energy along power lines. They step-up or step-down voltage for power distribution, directing electricity safely to your home or business. There are different types of transformers, like those with oil insulation for cooling, or Dry-Type power Transformers which use air to cool their electrical core. Transformers come in various sizes and are used in industries, commercial buildings, and even in renewable energy systems like wind or solar farms. You may hear dry-type transformers called by other names including: cast resin transformer, solid-state transformer, air-cooled transformer, non-liquid-filled transformer, resin-filled transformer, non-oil-filled transformer.

In this post we’re focusing on Dry-Type power Transformers as they gain in popularity for their safety features, environmental friendliness, and reduced maintenance requirements. Now let’s continue our learning with Encapsulated Dry Power Transformers.

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Encapsulated Versus Non-Encapsulated Dry Power Transformers

Encapsulated (non-exposed) dry-type power distribution transformers, also known as cast-resin transformers, provide better protection, environmental friendliness, and require less maintenance, while non-encapsulated transformers offer flexibility, cost-effectiveness, and potentially higher efficiency. You may also hear them called non-oil filled transformers, a reference to Oil-filled transformers which use liquid for cooling.

A contributing factor for encapsulated transformers needing less maintenance is their windings aren’t exposed to external conditions, while non-encapsulated dry-type transformers typically have windings and insulation materials exposed to the air without encapsulation. This post will focus on Encapsulated Transformers.

When to Choose Encapsulated Dry-Type Transformers

When it comes to construction, encapsulated dry-type transformers use insulation materials made of resin that surround the windings. This helps protect them from moisture, dust, and contaminants. The resin insulation is also great at resisting fire and reducing the risk of oil leaks.

If you’re looking for an environmentally friendly solution, encapsulated dry-type transformers have an edge over non-encapsulated transformers. They don’t contain oil or other hazardous substances. This means they don’t pose a risk of oil spills or leaks. Plus, when it’s time to dispose of them, it’s relatively easier and safer.

When choosing a dry-type transformer, you’ll either want a single phase or three-phase transformer. “Phase” refers to the number of conductors or windings used in the transformer’s primary and secondary circuits. It represents the number of separate electrical paths through which current can flow.

Single-Phase Transformers are commonly used in residential applications and small commercial setups. Three-Phase Transformers are used in industrial and commercial for large motors, machinery, and heavy loads.

Dry Transformer Maintenance and Safety Considerations

Maintenance-wise, you’ll require less upkeep with the encapsulated dry-type. Their sealed construction means you don’t have to monitor oil levels or do regular oil changes. This makes them ideal for installations where maintenance access is limited or where managing oil can be challenging.

In terms of safety, encapsulated dry-type transformers stand out. The transformer’s resin insulation used is self-extinguishing for high fire resistance. In the event of over-heating or fire, they give off low levels of toxic gases and smoke, making them ideal for indoor installations.

5 Applications for Dry-Type LV and MV Transformers

Commercial Buildings: Offices, shopping centers, hotels, and hospitals. For lighting, HVAC systems, elevators, and other electrical loads.

Industrial Facilities: manufacturing plants, refineries, mining operations, and warehouses. For powering machinery, equipment, motors, and control systems, giving efficient and safe operation.

Renewable Energy Systems: examples included wind farms and solar power installations. For converting and distributing electricity into the grid or local distribution networks.

Renewable Energy Systems: examples included wind farms and solar power installations. For converting and distributing electricity into the grid or local distribution networks.

Data Centers: for power distribution and voltage conversion in IT servers, network equipment, cooling systems, and other key infrastructure. Fire-resistance and enviro-friendly, dry-type transformers are common in data center environments.

Residential Buildings: In urban settings, for safe and reliable power for lighting, appliances, and household electrical settings especially where low maintenance is needed.

“Electricity is the greatest gift to human kind, making it equally important to understand how to use it safely.” – Unknown

General Maintenance Procedures for Power Distribution Transformers

Start by visually inspecting your transformer, look for damage like cracks, loose connections, or overheating indicators. Next, clean transformer surfaces, remove dust, dirt, debris. Use a soft brush or compressed air to clear cooling vents and openings for best airflow.

After cleaning transformer surfaces, do an insulation resistance test (using Megohmmeter tool). This identifies any potential issues with insulation breakdown or moisture coming in. Next, tighten electrical connections. Loose connections lead to excess heat generation and possible transformer failure.

Finally, Operate and monitor your transformer temperature. See OEM documentation for the recommended temperature monitoring tool. Do a dielectric strength test to verify the insulation’s performance with high voltages. Keep detailed records of all maintenance activities, including test results, inspections, and replacement. Remember to consult the manufacturer’s guidelines and work with a qualified transformer maintenance and testing service while performing maintenance on dry-type transformers. Safety first!

Power Ranges, Voltage Levels and Voltage Classes for Choosing Low and Medium Voltage Transformer Sizes

Transformer Power RangeTransformer Voltage LevelTypical Voltage Classes
Up to 1,000 kVALow Voltage208V, 240V, 480V, 600V
Medium Voltage2.4 kV, 4.16 kV, 6.6 kV, 7.2 kV
High Voltage11 kV, 13.8 kV, 22 kV, 33 kV
1,000 kVA – 5,000 kVALow Voltage208V, 240V, 480V, 600V
Medium Voltage2.4 kV, 4.16 kV, 6.6 kV, 7.2 kV
High Voltage11 kV, 13.8 kV, 22 kV, 33 kV
Above 5,000 kVALow Voltage208V, 240V, 480V, 600V
Medium Voltage2.4 kV, 4.16 kV, 6.6 kV, 7.2 kV
High Voltage11 kV, 13.8 kV, 22 kV, 33 kV

Voltage levels shown above represent common instances and can vary based on the needs of your project and local regulations. Depending on the manufacturer and application, there can be multiple voltage levels available within each power range. A trained engineer can identify the correct voltage for your specific purpose.

Transformer Anatomy: Know What’s Inside Your Equipment

The Core: The core is like the heart of the transformer. Typically made of laminated steel, the transformer core provides a magnetic path for the flow of energy within the transformer.

Transformer Windings:  Veins and arteries of the transformer. Transformer windings are made of copper or aluminum conductors and carry electrical current. The primary winding receives input voltage, while the secondary winding delivers output voltage.

Insulation: Insulation is the protective armor of the transformer. In dry type transformers, typically made of resin or epoxy. Keeps windings insulated from each other, provides resistance against moisture, dust, and contaminants.

Enclosure: Outer shell of the transformer. Protects internal components from physical damage. The enclosure is made of materials like steel or aluminum and may have cooling fins or ventilation openings for heat dissipation.

Terminals: Connection points to power sources and loads, the bridge between the transformer and the electrical system it serves.

Cooling System: Dry type transformers often have a cooling system to dissipate heat. This includes natural convection cooling, forced air cooling, or heat sinks.

Protective Devices: Some dry type transformers have built-in protective devices, like temperature sensors or overcurrent protection. They safeguard against overheating or excessive currents.

See your manufacturer’s documentation for detailed information on your specific transformer model before doing maintenance or testing.

Regulating Power with Transformer Safety and Reliability

The next time you see a transformer in your facility, think of it as the traffic cop of the electrical world, where Safety and Reliability keeps power flowing smoothly. If you’re planning to replace a transformer, need maintenance or testing, Relectric can help. Contact one of our sales and service consultants today at 844.944.7372