Rectifier Transformers
High Current Rectifier Transformers for AC/DC Industrial Applications
Specialtrasfo is a global leader in designing and manufacturing high current rectifier transformers specifically engineered for the toughest AC/DC industrial applications. Our oil-immersed rectifier transformers power some of the most demanding processes in aluminium smelting, graphite manufacturing, mining, hydrogen production, copper refining, and steel plants.
Our transformers are built to handle extreme high current rectifier loads with unparalleled reliability and performance. Designed for heavy industry in some of the harshest industrial environments worldwide, Specialtrasfo transformers ensure operational stability, long service life, and compliance with rigorous industrial standards.
DC Voltage up to
1000 V
DC current up to
180 kA
AC primary voltage up to
145 kV
Sectors in which the Rectifier is applied
Our Expertise
- Transformer capacity: up to 180 MVA, optimized for large-scale rectifier loads
DC voltage: up to 1000 V for industrial DC power systems
DC current handling: up to 180 kA, ideal for ultra-high current applications in mining, aluminum, and steel industries
AC primary voltage: up to 145 kV, suitable for high voltage grid connection
Maximum transformer weight: 300 tons, engineered for robust industrial environments
Configurable transformer units: including single bridge, double bridge, double star with IPT (Interphase Transformer), and two double stars with IPTs
Multi-pulse topologies: from 12-pulse to 72-pulse units to reduce harmonics and improve power quality
Integrated regulating autotransformer: for on-load coarse voltage regulation within the same tank
Saturable reactors: included for on-load fine voltage regulation, enhancing operational flexibility
We manufacture transformers for electrolytic plants. In this case both bridge and double star with interphase transformer circuits are frequently used. Coarse voltage regulation is often obtained by means of an on-load tap-changer (OLTC) operating on taps made on primary windings. We design the cooling system of a rectifier transformer with particular attention to the current harmonics arising from the rectifier operation, which can otherwise cause very high eddy current losses. This becomes very important in transformers for electrolytic plants and for SCR power circuits, where high values of delay angle determine very fast commutations.
In small oil immersed units natural cooling (ONAN) is utilized. In larger units cooling is mostly obtained by forced circulation of either oil and water (OFWF) or oil and air (OFAF) in a cooler connected by oil pipes to the transformer tank.
The cooler acts as a heat exchanger with the heat flowing from either the oil to the water (OFWF) or the oil to the air (OFAF). In the case of OFWF cooling, two coolers are usually provided. Each of them is rated for the full transformer losses, so that the transformer can be kept running at its full load in the event of a failure of either a cooler itself or its auxiliary equipment.
In conjunction with thyristor or diode rectifiers, these transformers form the link between the AC and the DC systems of the industrial plant. Their development and construction requires extensive experience as well as deep theoretical knowledge.
Case History
DC Current 105 kA
DC Current 105 kA
Secondary voltage regulation 26 V to 360 V with 33 position OLTC
Secondary voltage regulation 26 V to 360 V with 33 position OLTC
Rated power 2x26.000 kVA
Rated power 2x26.000 kVA
24 pulse reaction (12 pulse with 4 units in parallel)
24 pulse reaction (12 pulse with 4 units in parallel)
Saturable reactors
Saturable reactors
Weight 195.000 kg
Weight 195.000 kg
Case History
DC Current 105 kA
DC Current 105 kA
Secondary voltage regulation 26 V to 360 V with 33 position OLTC
Secondary voltage regulation 26 V to 360 V with 33 position OLTC
Rated power 2x26.000 kVA
Rated power 2x26.000 kVA
24 pulse reaction (12 pulse with 4 units in parallel)
24 pulse reaction (12 pulse with 4 units in parallel)
Saturable reactors
Saturable reactors
Weight 195.000 kg
Weight 195.000 kg
Combined Tests
Our facilities are equipped to test all transformer-rectifier combined systems within our production range.
15 MVA supply power for the test
15 MVA supply power for the test
Combined Tests
Our facilities are equipped to test all transformer-rectifier combined systems within our production range.
15 MVA supply power for the test
15 MVA supply power for the test
Combined tests
15 MVA supplied power for the test
15 MVA supplied power for the test
Equipped to test transformer + rectifier combined systems with all type of cooling: ONAN - ONAF - OFWF - OFAF
Equipped to test transformer + rectifier combined systems with all type of cooling: ONAN - ONAF - OFWF - OFAF