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Traction transformer repairs

The onboard traction transformer as a crucial part of the traction chain adapts the electrical voltage coming from the overhead power lines to the lower voltage levels needed within the traction chain. It also feeds auxiliary converters for other electrical systems like lighting, heating, and or onboard information systems. If the traction transformer fails, the planned train traffic schedule may be disturbed and leading to passenger inconvenience, and even costly penalties may be incurred.


Scope of work

A traction transformer is highly reliable and designed to perform under harsh conditions. However, to prevent unpredicted failure and ensure a long lifetime, some services are advised during the whole life cycle. The operating conditions of a traction transformer differ highly from power transformers. Therefore the interpretation of condition checks has to be done by traction experts, otherwise misleading results may occur.

Regular oil analysis gives a good image of the actual health. Additionally, basic and advanced diagnostic tests can provide further information.

If an onboard traction transformer gets damaged by an accident or due to other reasons, we are able to fully repair the traction transformer by replacing damaged parts of the core, winding reclamping, partial or full winding replacement, and repair of the tank. At the end of such work, all electrical routine tests are done.

During the long life of a vehicle may some operational conditions change. An upgrade or replacement of some parts of the traction transformer can help to ensure further operation.

A midlife overhaul is recommended to ensure reliability in the second half of the lifetime. Here all traction transformers are systematically checked and maintained by replacing parts with lower life expectancy.

Distribution transformer repairs

Distribution transformers ranging from 315 kVA to 5 MVA are readily distributed across the distribution networks, forming an integral part of the overall distribution network.

Power transformer repairs

Few transformers fail due to old age per se, but rather as a consequence of external faults, short circuit faults, insulation failure (dielectric failure), local overheating (causing gassing) or accessory failure (e.g. bushings, tap changers, coolers, surge-arresters).

On-site repairs

Thanks to our TrafoSiteRepair offering we can refurbish, repair or upgrade your transformer directly at site avoiding transportation risk and time thus bringing your unit back on-line in weeks or even months faster than a workshop repair or a new transformer delivery.


Repairing a transformer instead of replacing it can substantially reduce investment costs and provide a faster turnaround than buying a new transformer.

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Transformer service

Aging assets, rising energy demand and the critical need to avoid unplanned outages are challenging utilities and industrials around the world. Hitachi Energy is the largest transformer service organization, Global expertise close to our customers.
Hitachi Energy Power Transformers


Hitachi Energy offers distribution and power transformers, Dry-type and EconiQ™ Transformers as well as services, for industrial and commercial applications.

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