Start with the decision you need to make
These resources help buyers turn an initial transformer requirement into a specification that can be discussed with a manufacturer. They distinguish confirmed OSTL facts from general technical guidance and identify the details that still need project-specific confirmation. They are not substitutes for an electrical design or a signed technical offer.
Dry type or oil filled?
Compare the installation, cooling, environmental and maintenance questions before choosing.
↗BUYER DUE DILIGENCEChoosing a manufacturer
Check scope, documents, design fit and quotation exclusions—not a headline claim alone.
↗RFQ WORKSHEETPrepare a useful quotation brief
A practical technical and commercial checklist, plus a copyable/downloadable template.
↗GENERAL TECHNICAL GUIDANCEUnderstanding routine tests
Learn what to ask about test scope and reports without assuming an unverified facility capability.
↗Choose a product line
Power Transformers
A project-specific starting point for power transformers up to 10 MVA and up to 66 kV.
↗PRODUCT LINEDistribution Transformers
Specify the load, voltage and site. Start a clearer distribution-transformer enquiry with OSTL.
↗PRODUCT LINEDry-Type Transformers
A confirmed OSTL product line. Define the installation and performance requirements before selecting the configuration.
↗Rating and location are separate questions
Use the 63 kVA to 10 MVA ratings enquiry guide for rating interests, and the existing regional pages for destination context. Include the delivery destination, site conditions and requested timeline alongside the electrical specification. The regional pages provide the right contact and project context.