A comprehensive guide to the selection and technical parameters of dry-type transformers: 10 key points that engineers and procurement are most likely to overlook

In practical projects, the problem of selecting the wrong model for dry-type transformers is very common.

The capacity is sufficient, but the temperature rise exceeds the standard;
Voltage matching, but noise is not qualified;
Parameter compliance, but overseas acceptance failed.

This article will delve into the most critical but easily overlooked technical details of dry-type transformers from the perspective of engineering selection.

1.Capacity selection: You cannot just look at kVA

1.1 Continuous load and intermittent load

Dry-type transformers are highly sensitive to ambient temperature and require appropriate derating in the following scenarios:

• high altitude
• high temperature environment
• Closed computer room

1.2 Overload Capacity Assessment

The short-term overload capacity of epoxy cast dry-type transformers is significantly weaker than that of oil immersed transformers, and the load curve needs to be evaluated in advance.

2.Voltage level and wiring group

Common combinations:

• 10kV / 0.4kV
• 20kV / 0.4kV

The wiring group should match the system protection logic, such as:

• Dyn11
• Yyn0

3.Insulation level and temperature rise design

Insulation Class	Typical Temperature Rise
Class F	100K
Class H	125K

When choosing, consider long-term operating temperature rather than short-term limits.

4.Selection of cooling method

AN: Natural cooling, low noise
AF: Forced air cooling, capacity can be increased by 30-40%

But the reliability and maintenance of the fan also need to be taken into consideration.

5.Partial discharge level

High quality dry-type transformers typically require:

• Partial discharge ≤ 10 pC

This is one of the core indicators for overseas project acceptance.

6.Noise control

Noise often becomes a veto in data center and commercial building projects.
Attention should be paid to:

• core structure
• Shock absorption design
• Installation foundation

7.Protection level and environmental adaptability

Common levels:

• IP00 (indoor)
• IP23/IP31 (anti drip, anti foreign object)

8.Energy efficiency and loss indicators

Critical loss parameters:

• no-load loss
• load loss

The EU and North American markets have particularly strict requirements for this.

9.Standards, certifications, and documents

Common requirements:

• IEC / IEEE
• CE
• ISO system documents

10Hidden risks of export projects

Wooden crate packaging standard
Shipping moisture prevention
Technical document language

Dry-type transformers are not necessarily “the better the parameter table, the safer it is”, but rather highly coupled system equipment with application scenarios.
The truly professional selection is a comprehensive reflection of technical understanding, engineering experience, and standard awareness.

Luoyang Datang Energy Technology Co., Ltd. is a high-tech enterprise integrating R&D, manufacturing and supply of power equipment such as transformers, new energy components, distribution cabinets and inverters. With technological innovation as the core, we focus on creating high-reliability and high-performance power solutions to serve global customers. With a strict quality control system and international standard certification, we continue to output excellent products and enable customers to build safe and stable power systems.