Reconditioned transformers

Reconditioned transformers

Reconditioned transformers (also called remanufactured transformers) are refurbished transformers that undergo a thorough inspection, testing, and repair process to restore them to optimal working condition. As key players in electrical systems, transformers transfer energy between circuits at different voltage levels. Over time, wear and tear can lead to decreased performance. Reconditioning aims to extend a transformer’s lifespan by replacing worn-out components, repairing damage, and conducting tests to meet specified standards. This cost-effective alternative is particularly useful when existing transformers have remaining operational life but require maintenance. It aligns with sustainability goals by maximizing the use of resources.

Initial inspection

The initial inspection involves a thorough visual examination and a comprehensive review of historical records. Experts scrutinize external components, such as bushings and tap changers, for signs of wear, corrosion, or damage. The inspection extends to insulating materials and core and winding surfaces, with a focus on identifying any issues that may impact the transformer’s performance. Efficient cooling systems are also assessed for blockages or malfunctions. Detailed inspection forms the basis for a targeted reconditioning strategy, ensuring that specific issues are addressed, and contributing to the restoration of the transformer to optimal operational condition


The next step is precise disassembly of the unit to access internal components. Utilizing specialized tools, components such as bushings, tap changers, and insulation are systematically removed, with each part documented for a thorough evaluation. Attention is focused on the core and winding assembly, checking for signs of damage or degradation. The phase also allows for an assessment of mechanical integrity, highlighting any structural abnormalities or wear. This detailed disassembly sets the stage for targeted interventions and repairs, ensuring the transformer can be seamlessly reassembled to restore optimal performance and reliability.


The cleaning phase is a process following dismantling, aiming to restore the unit to optimal condition. Utilizing specialized cleaning agents and techniques, it focuses on eliminating contaminants and outdated insulation materials from both the core and winding surfaces. Beyond enhancing aesthetics, this step is crucial for improving the transformer’s efficiency and performance. The process also includes a detailed inspection of insulating materials to address any signs of wear or deterioration. Overall, the cleaning phase prepares the transformer for subsequent testing.


The testing stage involves comprehensive electrical assessments to ensure the unit’s integrity and performance. Tests measure parameters like winding resistance, insulation resistance, and dielectric strength, identifying potential short circuits or anomalies developed during the transformer’s operational life. The turns ratio test confirms output consistency and adherence to specified standards. Post-reconditioning, a repetition of these tests verifies the success of repair and replacement interventions, serving as a final checkpoint for safety, efficiency, and reliability. This phase not only confirms compliance with standards but also provides valuable data for ongoing performance analysis, reinforcing the commitment to delivering a reconditioned transformer that exceeds expected benchmarks.

Repair and Replacement

In this step, damaged or worn-out components, such as bushings, tap changers, and insulation materials, undergo targeted repair or replacement. This process not only addresses visible issues but also enhances the transformer’s overall reliability. Measures include repairing damaged winding surfaces, treating corroded parts, and reinforcing structural elements. Replacement parts are chosen in adherence to industry standards to ensure compatibility and optimal performance. The focus on safety and performance standards underscores the importance of this phase in extending the transformer’s lifespan and ensuring its sustained contribution to a reliable electrical system.

Oil Processing

Oil processing begins with purifying the insulating oil, eliminating moisture, gases, and contaminants using specialized filtration units. In cases of irreparable oil quality, replacement with high-grade insulating oil may be necessary. Vacuum treatment is often employed to remove dissolved gases, enhancing the oil’s dielectric properties and overall insulation performance. 

Vacuum and Pressure Impregnation

The vacuum and pressure impregnation phase is a crucial step focused on enhancing insulation properties. By subjecting the transformer to a vacuum, air and moisture are efficiently removed from the winding and core structures. Subsequently, the unit is immersed in a specially formulated insulating varnish or resin under pressure, ensuring comprehensive penetration of the material into every crevice. This process reinforces insulation, reduces the risk of electrical discharges, and enhances the transformer’s ability to withstand environmental stress. Serving as a preventive measure, it offers a durable shield against issues like moisture ingress and mechanical vibrations, contributing significantly to the overall resilience and longevity of the remanufactured transformer.

Testing (Post-Reconditioning)

The final testing phase ensures the reconditioned transformer meets or exceeds industry standards for safety and performance. Repeating initial electrical assessments, including winding resistance, insulation resistance, and dielectric strength measurements, reaffirms the success of repair and replacement efforts. The turns ratio test is reiterated to confirm consistent output and compliance with specified standards. This comprehensive testing serves as the ultimate checkpoint, providing assurance that the transformer is not only in line with safety and efficiency standards but also offering valuable data for ongoing performance analysis. 

Painting and Finishing the reconditioned transformers

Following the repairs and testing, a high-quality protective coating is applied to safeguard the transformer from corrosion and environmental elements. Carefully chosen for durability, this coating not only enhances the unit’s longevity but also revitalizes its external appearance. The painting completes the reconditioning journey, ensuring the transformer is not only functionally robust but also visually renewed.


Reconditioning transformers is a complex process that requires numerous steps to finish as well as meet specific standards and regulations. On the other hand, remanufactured transformers are a cost-effective solution for many businesses and organizations.

If you’re looking for top-class transformer solutions at reasonable pricing, at TTES, we have over 100 combined years of experience manufacturing, maintaining, and repairing transformers of all types. If you’re looking for industry-leading lead times of just 20 weeks on average, don’t hesitate and reach out to us for a free quote!

Categories :

Share This Article :

Satisfaction guarantee

With our OEM network and 100+ years experience, we ship in 20 weeks. Transparency and satisfaction guaranteed on every projects.

Get your transformer at an unrivaled speed