Heavy Industry Process Transformers: Electric Arc Furnace (EAF) & Green Hydrogen Rectifiers

Electrodynamic short-circuit forces from 100 kA arc furnace currents, cyclic thermal stress, OFWF water cooling, and 24-pulse phase-shifting rectifier bridges f

1. Extreme Process Duty in Steelmaking & Hydrogen Production

Process transformers endure severe mechanical and electrical stresses far exceeding standard distribution equipment:

  • EAF Transformers: Low secondary voltage (400 - 1200 V) with massive currents up to 120 kA.
  • Green Hydrogen Electrolysers: Continuous high-current DC supplies via multi-pulse rectifiers.

2. Technical Comparison: EAF vs Hydrogen Electrolyser Transformers

ParameterElectric Arc Furnace (EAF) UnitGreen Hydrogen Rectifier Unit (PEM / Alkaline)
Secondary Current60 kA - 120 kA AC10 kA - 40 kA DC per bridge
Short-Circuit Frequency10 to 20 dead short-circuits per heatSmooth continuous DC load
Cooling MethodForced Oil-Water Heat Exchangers (OFWF)Forced Oil-Air (ONAF / OFAF)
Pulse ConfigurationDirect furnace electrodes24-Pulse (± 7.5° phase-shifted)

3. Electrodynamic Short-Circuit Force Formulation

Electrodynamic radial and axial forces on transformer windings scale with current squared (I2):

Fradial = (μ0) / (2) · ((N · Isc) / (hw))2 · 2π Rw

To withstand 120 kA short-circuit forces, EAF coils use hardened copper conductors clamped under 10 MPa hydraulic pressure.

4. 24-Pulse Harmonic Cancellation in Electrolysers

Electrolyser transformers split secondaries into four phase-shifted systems (+22.5°, +7.5°, -7.5°, -22.5°), canceling all harmonic currents up to the 23rd harmonic and achieving THD-I < 4.0%.

*Reference: IEEE Std C57.18.10-2021; IEC 61378-1:2011.*