Transformer Basics: Complete Guide to Power Transformers

1. What is a Transformer?

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It converts voltage levels while maintaining the same frequency, enabling efficient long-distance power transmission and distribution.

2. Transformer Types

• Dry-Type Transformer: Uses air cooling, fire-resistant, safe for indoor use. Common models: SCB10, SCB11, SCB12, SCB13.
• Oil-Immersed Transformer: Uses mineral oil for cooling, high efficiency for outdoor use. Common models: S11, S13, S22.
• Instrument Transformer: Current transformers (CT) and potential transformers (PT) for measurement and protection.

3. kVA Sizing Guide

• Standard range: 30kVA – 3150kVA for dry-type; up to 10MVA for oil-immersed.
• Formula: kVA = (V × I × √3) ÷ 1000 (3-phase)
• Rule of thumb: Size at 80% load for optimal efficiency; add 20% for future expansion.

4. Cooling Methods

• AN (Air Natural): Natural air circulation — standard for dry-type.
• AF (Air Forced): Fans for forced air cooling — higher capacity.
• ONAN (Oil Natural Air Natural): Oil circulation with natural air — standard for oil-type.

5. IEC Standards

Ziyao transformers comply with IEC 60076 series (Power Transformers), IEC 62271 (Switchgear), and IEC 61439 (Low-voltage Switchgear). Certification: ISO 9001, ISO 14001.