Introduction
This article explains why silicon steel sheets are used for transformer cores, covering loss and magnetization. Transformers are the equipment that steps voltages up and down in power systems, and their design determines efficiency, reliability and maintenance cost. This article explains the main transformer types and the operating and maintenance points that engineers must control.
Transformer Types
Distribution transformers are commonly oil-immersed, with the windings and core immersed in insulating oil that cools and insulates. Hermetically sealed transformers use a sealed tank that breathes through a membrane or gas cushion, reducing oil oxidation and moisture ingress. Instrument transformers, current and voltage types, feed metering and protection circuits, and pole-mounted transformers supply single and three phase loads from overhead lines.
Core and Winding Materials
The core is built from grain-oriented silicon steel laminations that conduct magnetic flux with low loss, and the windings are copper or aluminum conductors insulated for the system voltage. Core losses and copper losses are the two components of transformer losses, and the grade of the silicon steel directly affects the no-load loss of the unit.
| Type | Function | Feature |
|---|---|---|
| Distribution | Step voltage for use | Oil-immersed cooling |
| Hermetically sealed | Isolated from air | Low oil oxidation |
| Instrument CT/VT | Feed metering | Ratio accuracy |
| Pole-mounted | Overhead supply | Single/three phase |
Operation and Maintenance
Regular patrol inspection covers oil level and temperature, leakage, noise, and the condition of bushings and connections. Oil sampling and dissolved-gas analysis detect developing faults such as overheating and partial discharge, and transformer oil leakage is repaired by sealing the gasket or weld while the oil is drained and handled safely.
Selection of a Transformer
Select the transformer by the required kVA rating, the primary and secondary voltages, the connection group, the impedance and the loss level. The load profile and the ambient temperature determine the rating, and the efficiency class is chosen by the capitalized cost of losses over the service life.
Verification and Documentation
Confirm the rated data, the test certificates for ratio, impedance, losses and insulation, and the oil test results on delivery. The routine tests and the type tests should be documented for the unit.
