Marine Air-cooled Resin Cast Rectifier Transformer

The Marine Air-cooled Resin Cast Rectifier Transformer converts the input three-phase AC power into two three-phase AC lines with a phase difference of 3n degrees electrical angle, which are used to power the inverter's rectifier section, resulting in 12-pulse rectification. When both propulsion branches operate simultaneously, the transformer front-end grid achieves virtual 24-pulse rectification, significantly reducing harmonics introduced by the inverter. Similarly, multi-pulse rectification, such as 6, 18, and 24 pulses, can be achieved.

The Marine Air-cooled Resin Cast Rectifier Transformer primarily consists of a housing, the transformer body, and a water-cooled cooling device.

1. Transformer Body
1) High-Voltage Winding
The winding utilizes a segmented cylindrical structure, with 100% oxygen-free copper conductors. The intersegments and interlayers are fully insulated with insulating material. The formed coil is placed in a heated mold and cast in a specially formulated resin within a vacuum chamber. This vacuum process effectively removes gases from the winding, ensuring the transformer exhibits low partial discharge characteristics. Because the thermal expansion coefficients of the conductor and the casting resin are very similar, thermal stress differences caused by load changes are minimized, significantly enhancing the winding's crack resistance. Ultimately, the winding solidifies into a fiberglass-like structure, providing excellent short-circuit and lightning surge resistance.
2) Low-Voltage Winding:
The low-voltage coil is wound with copper foil (or aluminum foil), with interlayer and end insulation using epoxy resin prepreg. Heat dissipation ducts are placed in the center as needed. After winding, the coil undergoes a high-temperature curing process according to a predetermined curve, tightly bonding the prepreg and foil to form a solid, integrated structure. The coil ends are then sealed with epoxy resin to enhance moisture resistance. This coil structure features high turn-to-turn capacitance, balanced ampere-turn distribution, and uniform axial temperature distribution, facilitating heat dissipation and improving short-circuit and lightning surge resistance. It also exhibits excellent dynamic stability in high-capacity, low-voltage transformers.
3) Vacuum Casting
The winding is manufactured in automated vacuum casting equipment, strictly adhering to a predetermined curing temperature curve throughout the process to ensure molding quality. The vertical casting process facilitates smoother gas discharge from the windings, reducing residual bubbles. During the casting process, the equipment precisely controls the ratio of the resin components in real time. Static mixing technology ensures uniform mixing of the resin and curing agent, while continuously controlling the vacuum level in the casting environment, fundamentally eliminating potential casting defects. This process significantly improves the mechanical strength and overall density of the windings. Compared to traditional impregnation products, it offers greater mechanical resistance and excellent short-circuit resistance, ensuring stable operation of the transformer under harsh operating conditions.
4) Core Structure
The core is constructed from high-quality cold-rolled, grain-oriented silicon steel sheets, sourced from Baowu Group or imported high-permeability cold-rolled electrical steel strip. Precision-machined using advanced automated shearing lines, the core ensures precise sheet dimensions and minimal burrs. The core structure features a seven-step, 45° fully beveled joint, with positioned laminations and a non-stacked yoke process, effectively reducing no-load losses and current. The core surface is bonded with a high-temperature-resistant resin to enhance overall structural strength. It is also treated to resist moisture and corrosion, resulting in excellent low-loss and low-noise performance.
2. Housing
The housing meets IP44 protection, isolating the inside and outside of the housing, making the transformer's internal environment virtually unaffected by external influences.
The housing utilizes a frame structure, integrating the transformer and housing into a single unit for shock resistance.
3. Water-Cooled Cooling System
The water cooler consists of a water-cooling system chamber, a centrifugal fan, and a heat exchanger. The heat exchanger has water inlets and outlets, and the water cooler is equipped with a water leak detector.

1. Compact overall structure, excellent ventilation and heat dissipation, simple installation, easy replacement, and easy maintenance;
2. Dual-winding, double-split structure; the high-voltage winding is cast with epoxy resin, which is moisture-resistant and suitable for marine environments;
3. The two sets of secondary windings have a 30-degree electrical angle offset between the in-phase windings, enabling 12-pulse rectifier circuit power supply. Similarly, multi-pulse rectifier circuits such as 6-pulse, 18-pulse, and 24-pulse circuits can be powered;
4. If equipped with a water-cooling device, it can quickly and effectively dissipate heat generated by the transformer during operation, significantly reducing heat dissipation in the cabin.

Implementation Standards: IEC60146, IEC60076
Voltage Levels:
Grid Side: 6, 6.3, 6.6, or custom-made
Valve Side: 1 kV or less, or custom-made
Capacity Range: 1000–5000 kVA
Voltage Regulation Range and Method: ±5%, ±2 x 2.5%, Off-Excitation Voltage Regulation
Frequency: 50 Hz
Transformer Combination: Two units for 12-phase, 24-pulse operation
Connection Group: Dy11d0 (+7.5°) and Dy1d2 (+7.5°) or customizable
Cooling Method: AN/AF
Load Rating: Class VI (customizable)
Insulation Thermal Resistance Class: Class F, Class H
Partial Discharge: ≤10pC

3kV and below: Power frequency withstand voltage 10kV, impulse withstand voltage 20kV
10kV: Power frequency withstand voltage 35kV, impulse withstand voltage 75kV
35kV: Power frequency withstand voltage 70kV, impulse withstand voltage 170kV