Technical Details – High-current Transformer
1. Overview
A High-Current Transformer is a specially designed transformer that delivers very high current at low to moderate voltage levels. These transformers are typically used for industrial processes like electrolysis, arc furnaces, welding, and testing laboratories.
2. Applications
- Electric arc furnaces (EAF)
- Induction heating systems
- Electroplating and electrolysis
- High-current test benches (e.g., for circuit breakers, cables)
- Resistance welding
- Short-circuit testing in labs
3. Electrical Specifications
|
Parameter
|
Typical Range
|
|---|---|
|
Primary Voltage
|
400 V to 33 kV (based on input supply)
|
|
Secondary Voltage
|
1 V to 1000 V (application-specific)
|
|
Secondary Current
|
Several kiloamperes (1 kA to 100 kA or more)
|
|
Frequency
|
50 Hz / 60 Hz (or lower for special cases)
|
|
Power Rating
|
100 kVA – 10 MVA+ depending on load
|
4. Design Features
- Low secondary voltage, high current output
- Massive cross-section copper windings to handle high currents
- Robust insulation system for high thermal stress
- Often equipped with air or water-cooled busbars on secondary side
- Impedance carefully controlled to match application (e.g., furnace, test load)
5. Cooling Methods
- ONAN – Oil Natural Air Natural
- OFAF – Oil Forced Air Forced (for higher loads)
- Water-cooled secondary terminals (especially in arc furnace transformers)
- Dry-type with forced air for indoor high-current test labs
6. Transformer Types by Application
|
Application
|
Transformer Type
|
Output Current
|
|---|---|---|
|
Arc Furnace
|
Oil-immersed, heavy-duty
|
10 kA – 100 kA
|
|
Electrolysis
|
Rectifier-coupled transformer
|
5 kA – 50 kA
|
|
Welding
|
Dry type, air-cooled
|
1 kA – 10 kA
|
|
Test Lab
|
Dry/oil type, precision
|
0.1 kA – 10 kA
|
7. Protection and Instrumentation
- Overcurrent relays
- Temperature sensors (OTI, WTI)
- Cooling system interlocks
- Current and voltage monitoring
- Buchholz relay (for oil-filled types)
8. Mechanical Considerations
- Reinforced terminals for heavy current conductors or busbars
- Compact winding layout to minimize leakage reactance
- Often mounted on skids or base frames for stability
- Secondary terminals may be flexible braided copper or bolted lugs
9. Standards
- IEC 60076 – General transformer standard
- IEC 60146 – Semiconductor converters (for rectifier units)
- IEEE C57 series – Power and furnace transformers
- IS 2026 – Indian Standard for Power Transformers
10. Advantages
- Supports extremely high-current industrial processes
- Rugged design with high thermal endurance
- Customizable voltage/current outputs
- Can be integrated with rectifiers or power electronics
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