1. Overview

Mining transformers are used to supply power to underground and surface mining equipment. These transformers must withstand harsh environmental conditions such as high dust levels, mechanical vibrations, moisture, and temperature fluctuations.

2. Applications

• Powering underground drills, conveyors, crushers, and lighting systems
• Supplying voltage to mobile mining equipment
• Step-down transformation from medium voltage (MV) to low voltage (LV) for equipment use
• Portable substation applications in open-pit and underground mines

3. Design Considerations

a. Electrical Parameters

• Primary Voltage: Typically 3.3 kV, 6.6 kV, 11 kV, 22 kV (MV range)
• Secondary Voltage: 415 V, 690 V, or other LV values depending on mining equipment
• Frequency: 50 Hz or 60 Hz
• Power Ratings: Typically ranges from 500 kVA to 5 MVA
• Impedance: Customized to suit system protection coordination

b. Duty Type

• Designed for continuous or cyclic duty under load
• Must accommodate frequent starts and stops of mining equipment

4. Construction Features

• Type: Oil-immersed or dry-type (cast resin for fire-prone zones)
• Cooling: ONAN or AN (dry type); forced air (OFAF or ANAF) for higher capacities
• Core: Laminated CRGO silicon steel for low core losses
• Windings: High-conductivity copper or aluminum, vacuum impregnated or resin cast for durability
• Insulation Class: F or H class insulation for high-temperature operation

5. Mechanical and Safety Features

• Explosion-proof or flameproof enclosures (for hazardous underground zones)
• Ingress Protection (IP): IP55 or higher, suitable for dust and water exposure
• Vibration and shock resistance
• Portable skid-mounted versions for mobility
• Earthing and shielding to protect against stray voltages

6. Protection and Monitoring

• Buchholz relay (for oil-filled types)
• Temperature sensors and thermostats
• Overcurrent and earth fault protection
• Pressure relief devices
• Oil temperature indicators (OTI) and winding temperature indicators (WTI)

7. Standards and Certifications

• IS 2026 / IEC 60076: General transformer standards
• IEC 61378-1: For industrial converter transformers (if used with mining drives)
• MSHA / DGMS / ATEX: Certification requirements for explosion-proof units in hazardous zones
• IEEE C57: For transformer application and testing

8. Environmental Considerations

• Humidity resistance: For underground and tunnel operations
• Corrosion protection: Special coatings or stainless-steel enclosures in high-moisture or coastal regions
• Compact design: To fit through shafts and narrow underground tunnels

9. Common Configurations

10. Summary

Mining transformers are rugged, customized solutions engineered for high-reliability in harsh industrial conditions. They emphasize safety, portability, insulation resilience, and mechanical robustness. Selection depends on the mining method, equipment load, location (surface or underground), and national safety regulations.