Dry Type Transformers Guide: Key Features, Types, and How to Choose

 

Dry type transformers play a crucial role in modern electrical infrastructure, especially where safety, environmental protection, and low maintenance are key priorities. After reading this article, you will have a clear understanding of what are dry type transformers.

This article will focus on three core dimensions:

Key features: Analyze parameters that directly affect reliability, such as fire protection level (such as F/H grade insulation), cooling method (natural air cooling/forced air cooling), and noise control.

Mainstream types: Compare the applicable scenarios and cost differences of different structures (such as CRT vs VPI);

Selection strategy: From the load requirements, installation environment (such as high humidity/dust areas), and full life cycle costs (procurement + operation and maintenance), provide a feasible selection framework.

Through systematic sorting, it helps you avoid the risks of “over-configuration” or “insufficient performance” and accurately match project requirements.

Definition

Dry-type transformers are electrical equipment that do not use liquid (such as transformer oil) for insulation and cooling, but use air, gas or solid insulating materials (such as epoxy resin) for insulation and heat dissipation. Compared with traditional oil-immersed transformers, they have significant advantages in safety, environmental protection and maintenance convenience.

Typical Application Scenarios

Advantages and limitations of Dry Type Transformers

Core advantages

Adaptable to complex environments

The design without insulating oil makes it fireproof and explosion-proof, eliminating the risk of oil leakage, combustion or explosion, and is suitable for places with strict fire protection requirements such as high-rise buildings, subways, and data centers; the epoxy resin encapsulated winding can resist moisture, dust and chemical corrosion, and is suitable for harsh environments such as high-humidity coastal areas and dusty factory workshops.

Low maintenance cost

There is no need to regularly replace or test the insulating oil, which greatly saves long-term maintenance time and costs; there are no auxiliary equipment such as oil pillows and oil pumps in the structure, and the failure rate is low. Only daily cleaning and wiring inspection are required.

Flexible installation layout

Compared with oil-immersed transformers of the same capacity, dry-type transformers are smaller in size, lighter in weight, and occupy less space, which effectively reduces installation costs, and are especially suitable for installation scenarios with limited space.

 

High efficiency and energy saving

Using high-quality silicon steel sheets and amorphous alloy cores (high-end models), the no-load energy consumption is 10% – 30% lower than that of oil-immersed transformers.

Limitations

• High initial cost: Due to the use of epoxy resin casting or amorphous alloy core, its manufacturing cost is much higher than that of oil-immersed transformers, and the price is 30% – 50% higher at the same capacity. The cost-effectiveness is acceptable in small and medium capacity scenarios (such as ≤1600kVA), but the cost will rise sharply in ultra-large capacity scenarios (such as ≥2500kVA).

• Capacity and voltage limitations: The maximum capacity of a single dry-type transformer usually does not exceed 2500kVA, while the oil-immersed type can reach more than 100MVA. In high-power scenarios, multiple units need to be connected in parallel, increasing the complexity of the system; its mainstream product voltage level is concentrated in 10kV-35kV, and oil-immersed transformers are still the main ones in the ultra-high voltage field (such as 110kV and above).

• Limited heat dissipation capacity: The heat dissipation efficiency of dry-type transformers is lower than that of oil-immersed oil circulation cooling. It is easy to trigger overheating protection under long-term overload or high temperature environments, and often requires additional fans to assist in heat dissipation.

• Noise problem: During operation, the magnetostriction of the core and the electromagnetic force of the winding will generate 65-75dB of noise, which is higher than the 55-65dB of the oil-immersed type. When used in noise-sensitive areas such as hospitals and residential areas, sound insulation measures must be taken.

What are the classifications of dry-type transformers?

Classification by insulation method

Comparison of CRT and VPI features

 Classification by cooling method

Air Natural (AN)

Air natural relies on the natural air flow around the transformer to dissipate heat, and is suitable for dry-type transformers with small capacity and low voltage. This method is simple and reliable, but the heat dissipation effect is relatively weak.

Air Forced (AF)

Air forced is based on natural air cooling, and adds fans to force air flow to improve the heat dissipation effect. It is suitable for dry-type transformers with medium and large capacity and medium and high voltage. The fan is controlled by the transformer temperature and can effectively improve the cooling efficiency.

Purchasing guide for full life cycle cost 

Clear load requirements

1. Load capacity calculation: Calculate the required rated capacity (kVA) based on the total power of the equipment, the simultaneous coefficient and future expansion requirements to avoid insufficient or over-configuration of capacity. Reference formula: Transformer capacity = total power of the equipment × simultaneous coefficient/power factor (usually 0.8 – 0.9).

2. Voltage level matching: The input/output voltage must be consistent with the power grid and power-consuming equipment (such as 10kV/0.4kV), and special scenarios (such as photovoltaic grid connection) require customized design.

Environmental adaptability

1. Temperature, humidity and protection level: High temperature and high humidity environments (such as coastal areas) require H-level insulation (temperature resistance 180℃) and IP54 or above protection level; dust-intensive areas (such as cement plants) are recommended to match dust covers or fully enclosed cabinets.

2. Space limitation: For narrow distribution rooms, compact designs (such as SCB13 series) or split layouts are preferred.

Energy efficiency and cost

1. Priority on energy efficiency level: Select products that meet GB 20052 energy efficiency level 1 standard. The no-load loss is 20% – 30% lower than that of ordinary models, which can significantly save electricity costs in the long run.

2. Life cycle cost (LCC): Compared with the initial purchase price, maintenance costs and scrap recovery costs, high-end models (such as amorphous alloy dry transformers) have high initial investment, but the comprehensive cost over 10 years is lower.

Safety and certification

1. Fire protection and insulation level: Confirm that the product has passed the F-level (155℃) or H-level (180℃) heat resistance certification, and the flame-retardant epoxy resin casting process can meet the fire protection requirements of high-rise buildings.

2. International standard certification: Certification includes IEC, ANSI/IEEE, NEMA, CSA, etc.

Noise control

Office areas, hospitals and other scenes require noise ≤55dB. It is recommended to choose a low magnetic density core (such as below 1.3T) and a shock-absorbing base design; forced air-cooled models need to be equipped with a silent fan to avoid high-frequency noise interference.

Summary: Scientific investment to ensure stable operation

Dry-type transformers have unparalleled safety, reliability and energy saving in indoor or safety-critical scenes. However, when purchasing transformers, you should not only look at the price, but also pay attention to performance and quality.

SCOTECH Dry Type Transformer Features

Dry Type Transformer Workshop Photos

Whether you’re seeking a dry-type transformer for a demanding environment or a fully customized power solution, SCOTECH is your trusted partner for quality, reliability, and engineering excellence.

Contact our engineering team today for expert support and tailored quotations.