Converter Duty Transformer
High-Performance Converter Duty & Rectifier Transformers
Urja Techniques (India) Pvt. Ltd. is an established ISO-certified transformer manufacturer engineering specialized converter duty transformers (CDT), inverter duty transformers (IDT), and multi-pulse rectifier transformers rated up to 20 MVA in the 33 kV voltage class. Tailored explicitly for non-linear industrial loads, our transformers provide dynamic short-circuit strength and thermal stability across harsh operating conditions.
Modern electrical conversion systems—including silicon-controlled rectifiers (SCR), IGBT/thyristor converters, and variable frequency drives (VFD)—generate non-sinusoidal currents and steep voltage wavefronts (dv/dt). Standard distribution units experience severe hotspot overheating and insulation degradation under such harmonics. URJA's converter duty transformers are purposely constructed to withstand elevated eddy current losses, stray magnetic fields, and repeated mechanical stresses caused by continuous multi-pulse switching cycles.
Comprehensive Technical Specifications
Designed and manufactured in accordance with IEC 61378-1 (Converter Transformers), IEEE C57.18.10, and IS standards, each transformer is verified with comprehensive routine testing before dispatch.
| Rated Power Capacity | Up to 20 MVA (Custom design based on K-factor / Harmonic spectrum) |
| Rated Primary Voltage Class | Up to 33 kV (Class 11 kV, 22 kV, 33 kV) |
| Pulse Configurations | 6-Pulse, 12-Pulse, 18-Pulse, 24-Pulse Systems |
| Vector Groups & Phase Shift | Extended Delta, Star-Delta dual output (0°/30° phase shift for harmonic cancellation) |
| Winding Material | Electrolytic Copper / High-Conductivity Aluminium Foil-Wound with transposed conductors |
| Core Construction | High-permeability, cold-rolled grain-oriented (CRGO) silicon steel in step-lap mitered joints |
| Cooling Methodology | ONAN, ONAF, OFAF or Dry-Type (Cast Resin CRT / VPI) |
| Harmonic Derating Consideration | Calculated K-factor up to K-20; customized electrostatic shielding between windings |
| Standard Compliance | IEC 61378-1, IEC 60076, IEEE C57.18.10, IS 2026 |
| Protection & Instrumentation | WTI & OTI with contacts, Magnetic Oil Level Gauge (MOG), Buchholz Relay, PRV, Current Transformers |
Specialized Engineering & Key Design Highlights
Our converter duty configurations address the severe dielectric and electrodynamic stresses inherent in semiconductor rectification:
Harmonic Eddy Loss Mitigation
Employs continuously transposed conductors (CTC) and optimized foil winding topologies to limit proximity effects and stray losses induced by high-order current harmonics (5th, 7th, 11th, 13th).
Electrostatic Shielding
Fitted with grounded electrostatic copper screens between primary and secondary windings to block capacitive coupling, high-frequency transients, and DC voltage offsets from passing onto the supply grid.
Reinforced Mechanical Withstand
Rigid core-and-coil clamping designed to endure cyclic electromechanical forces during DC short circuits, dynamic commutation notches, and severe load swings.
Superior Thermal Margins
Engineered with directed cooling ducts and class-H / class-C thermal endurance margins ensuring low localized hotspot temperatures even under heavy continuous non-linear loadings.
Primary Applications Across Global Industries
URJA converter duty and drive duty transformers are operating reliably across demanding sectors globally:
- Solar Photovoltaic Inverter Duty: Multi-winding step-up transformers (split-inverter inputs) synchronizing central solar inverters to MV utility transmission lines.
- Variable Frequency Drives (VFD): Multi-pulse isolation and phase-shifting transformers for high-power motors in rolling mills, pumps, mining, and compressors.
- Electrochemical & Electrolysis: High-current DC rectifier transformers for chlor-alkali, zinc/copper electrowinning, aluminium smelters, and green hydrogen electrolyzers.
- Electric Arc & Induction Furnaces: Specialized supply units providing reliable stepping down with rapid tap-changing flexibility.
International Export Capabilities & Quality Approvals
Headquartered in Mumbai with a full-scale manufacturing complex in MIDC Rabale, Navi Mumbai, URJA Techniques serves global EPC contractors, industrial end-users, and public utilities. Our transformers are delivered to leading markets across the United Arab Emirates, Saudi Arabia, Kenya, Nigeria, Tanzania, South Africa, Vietnam, and Indonesia. Every unit undergoes strict routine and dielectric testing, verified by type testing at CPRI & ERDA laboratories.
Frequently Asked Questions
What makes a converter duty transformer different from a standard distribution transformer?
Unlike standard distribution units that experience sinusoidal loads, converter duty transformers are exposed to high harmonic currents, DC bias, and sharp voltage transients (dv/dt) caused by power electronics. URJA engineers these units with electro-static shields between windings, reinforced insulation, step-lap magnetic cores, and minimized eddy losses to resist overheating.
What configurations are available for multi-pulse drive operations?
We manufacture 6-pulse, 12-pulse, 18-pulse, and 24-pulse multi-winding configurations. For a 12-pulse converter, our dual secondary designs incorporate phase shifts (typically 30 degrees between Star and Delta LV windings) to eliminate the 5th and 7th harmonic orders directly at the source.
What is URJA's maximum manufacturing rating for converter duty units?
URJA manufactures converter duty, solar inverter step-up, and rectifier transformers up to 20 MVA capacity within the 33 kV voltage class, with cooling options including ONAN, ONAF, and dry-type VPI / Cast Resin.