1. By cooling method

● Oil-immersed transformer

● Dry-type transformer

2. By number of phases

● Single-phase transformer

● Three-phase transformer

3. By voltage regulation mode

● Off-circuit tap changer transformer

● On-load tap changer transformer

4. By application

● Power transformer

● Rectifier transformer

● Isolation transformer

● Distribution transformer

5. By core structure

● Core-type transformer

● Shell-type transformer