China Unit Auxiliary Transformer Manufacturers
Subian Electric manufactures unit auxiliary transformers (UAT) for power plants, substations and large industrial stations. The UAT supplies the station’s own auxiliary network from the generator or main transformer terminals, so its reliability directly affects plant availability.
Built and tested at our 50,000-square-metre factory in Xuzhou with 350+ employees, these units are engineered to plant duty – continuous loading, through-fault capability and robust documentation for project approval, backed by export to more than 50 countries since 2019.
Send the plant’s auxiliary load schedule and system voltage, and our engineers will confirm the rating, impedance and quotation.
Since 2019 · 50,000m² · 350+ Staff
Power Plant & Station Transformers
Unit auxiliary transformers and station transformers for power plant auxiliary networks, from medium ratings upward, engineered to plant availability standards.
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10kV Dry-Type Transformer-SCBH series Amorphous Alloy
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20-35KV Dry-Type Transformer
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20-35KV SCB Series Epoxy Resin Dry-Type Transformer
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20KV Oil-immersed Distribution Transformer
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35KV Oil-immersed Power Transformer
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6-10KV Oil-Immersed Power Distribution Transformer
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Current Transformer –10KV Indoor High Voltage
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Current Transformer–LMZK Wound Current Transformer300/5a
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Current Transformer–LSY-10 transformer Integrated CT
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current transformer–LXK high voltage zero sequence
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dry type distribution transformer-6-10 KV SCB series epoxy resin cast
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Electrical Transformers–JDZ – 10 Power Voltage
What Is a Unit Auxiliary Transformer?
A unit auxiliary transformer (UAT) supplies the auxiliary systems of a power plant or large station – the loads that keep the plant running, such as pumps, fans, control systems and lighting. It is fed from the generator or main transformer terminals, so it must keep supplying the auxiliary network even during plant events and through-fault conditions.
Because the UAT is part of the plant’s availability chain, it is engineered with specific attention to through-fault strength, overload capability, cooling and protection coordination with the auxiliary switchgear. Its rating is set by the auxiliary load schedule, typically a fraction of the main unit rating.
- Auxiliary network duty – continuous supply to plant systems.
- Through-fault strength – designed for system fault conditions.
- MV auxiliary voltages – engineered to plant system levels.
- In-house manufacture – core, winding and testing controlled.
- Documentation for approval – type tests and drawings for plant projects.
- Project support – impedance and protection coordination.
Auxiliary Transformer Arrangements
Plant practice varies; we build the two common arrangements plus their variants:
Unit auxiliary transformer
fed from the generator or unit terminals to supply the unit’s auxiliary network.
Station (common) auxiliary transformer
fed from the station bus to serve shared and start-up auxiliary loads.
Start-up / reserve transformers
providing backup auxiliary supply when the unit is out of service.
Unit Auxiliary Transformer Technical Data (Typical)
| Parameter | Specification |
|---|---|
| Duty | power plant / station auxiliary supply |
| Primary source | generator or HV bus terminals |
| Auxiliary voltage | 6.3 kV / 10 kV class and related levels |
| Rating | per auxiliary load schedule |
| Cooling | ONAN / ONAF |
| Through-fault | designed per plant fault study |
| Standard | IEC 60076 / GB 1094 |
Specifying a UAT: What the Factory Needs
The essential inputs are the auxiliary load schedule (connected and running loads with diversity), the auxiliary system voltage, the source connection (generator terminals or station bus), and the fault study values used for the plant’s protection design.
Cooling and enclosure follow the plant environment – outdoor units near the generator transformer need weatherproofing, while indoor installations may require specific clearances. Impedance is selected with the auxiliary switchgear’s fault rating in mind.
With those inputs we confirm the rating, impedance, cooling and test scope, and issue the design on drawings for the consultant’s review.
Engineering and Testing for Plant Duty
Plant auxiliary units follow a controlled build with additional mechanical and electrical checks, reflecting their role in plant availability.
Unit Auxiliary Transformer Quotation
Send the auxiliary load schedule, system voltage and fault study data, and our engineers will confirm the rating, impedance and factory quotation with the documentation list for your plant project.
OEM / ODM & Project Supply
Plant EPC contractors and OEMs take auxiliary transformers as part of complete power station packages.
OEM / ODM
Factory-Direct
Plant-specific designs with project documentation.
Factory direct · Test docs · Export support
Project Supply
Bundled Supply
Coordinated delivery with main transformers and switchgear.
Factory direct · Test docs · Export support
Distributor Support
Channel Partners
Technical support and tender documentation.
Factory direct · Test docs · Export support
Unit Auxiliary vs Main (Generator) Transformer
The main transformer steps the generator voltage up to the transmission level and carries the full unit output. The unit auxiliary transformer is smaller and feeds only the plant’s own systems, but it must be exceptionally reliable because losing the auxiliary supply can trip the whole unit.
Designing the two together – or at least confirming the UAT against the plant’s auxiliary scheme – avoids mismatches in impedance and protection. Our engineers coordinate the UAT rating and settings with the auxiliary switchgear specification.
Choosing a Unit Auxiliary Transformer Manufacturer
For a plant-critical unit, compare the through-fault capability evidence, the overload and cooling design, and the manufacturer’s type-test and reference record for similar units. Documentation quality matters as much as the hardware in plant projects.
Subian manufactures transformers under ISO9001, ISO14001, ISO45001, CE and UL certified systems, with a 110 kV type-test report and export experience across power, industrial and infrastructure projects in more than 50 countries.
Confirm the supplier can support the plant’s approval process – drawings, loss certificates and test formats are typically reviewed by the consultant before the unit is accepted.
Certifications & Quality Assurance
Our transformer production runs under ISO9001, ISO14001 and ISO45001 systems with CE and UL certification and type-test evidence to 110 kV class.
Product Certifications
10 kV Dry-Type Transformer Certificate
35 kV Transformer CB Certificate
35 kV Transformer CE Verification
Transformer CE Certificate
Dry-Type Transformer Test Verification
ISO 14001 Environmental Management
ISO 45001 Health & Safety
ISO 9001 Quality Management
110 kV Transformer Type Test Report
UL Certificate of Compliance
Unit Auxiliary Transformer Manufacturers FAQ
Questions about unit auxiliary transformers and their role in power plant supply.
What is a unit auxiliary transformer?
What is the difference between a unit auxiliary transformer and a main transformer?
How is the rating of a unit auxiliary transformer decided?
What voltages do unit auxiliary transformers use?
Why is through-fault strength important for a UAT?
Contact Subian
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