Transformers
Electrical Power & Distribution Transformers
Oil-immersed three-phase transformers, typically 25–2,500 kVA.
- Voltage ratio
- 11 kV / 433 V (typical)
- Cooling
- ONAN (oil natural, air natural)
- Vector group
- Dyn11 (typical)
Have a different requirement? Share your application and preferred configuration.
Made for the application.
Invitrona manufactures three-phase, oil-immersed transformers with natural oil and air cooling for distribution and industrial power duties, typically from 25 to 2,500 kVA. The usual arrangement steps 11 kV down to 433 V with a Dyn11 vector group and off-circuit tapping; other voltage ratios and fittings are agreed per project. The principal electrical, loss and installation parameters are fixed together so that a project team can move from a requirement to a focused specification.
Typical application contexts
- Industrial plant power distribution
- Commercial and institutional campuses
- Residential developments and townships
- Pumping stations and utilities
- Dedicated supplies for large machinery
Agreed electrical schedule
Rating, voltage ratio, vector group, impedance and tapping are fixed together in one schedule for the project.
Off-circuit tapping
Taps allow the secondary voltage to be adjusted to the actual supply level after installation, with the transformer isolated.
Oil-immersed construction
Natural oil and air cooling suits outdoor installation without auxiliary fans or pumps.
Protection fittings
Oil level, temperature and pressure fittings give the site the indications its protection scheme needs.
Project terminations
Bushings or cable boxes are arranged to suit the incoming and outgoing connections.
Technical specifications
Typical values for the product class. The ratings, options and operating conditions for your equipment are confirmed during engineering review and stated in the quotation.
| Parameter | Value | Condition |
|---|---|---|
| Rating range | Typically 25–2,500 kVA | Continuous duty, three phase |
| High-voltage winding | 11 kV class (typical) | 22 kV and 33 kV classes by assessment |
| Low-voltage winding | 433 V, three phase with neutral | Other secondary voltages by assessment |
| Frequency | 50 Hz | |
| Vector group | Dyn11 (typical) | Other groups to suit parallel operation or the system |
| Tapping | Off-circuit, typically ±5% in 2.5% steps | On-load tap changer by assessment |
| Cooling | ONAN (oil natural, air natural) | Mineral insulating oil |
| Impedance | Typically 4.5–6.25% | Depends on rating; stated in the quotation |
| Efficiency | Typically 98–99% | At rated load and unity power factor; depends on rating and loss level |
| Windings and core | Copper or aluminium windings; CRGO steel core | Selected for the rating and loss requirement |
| Fittings | Conservator, oil level indicator, breather, thermometer pocket, pressure relief device | Buchholz relay and winding temperature indicator by rating or project |
| Ambient and altitude | Up to 50 °C ambient; up to 1,000 m altitude | Derating for higher altitude |
| Installation | Outdoor plinth mounted; pole mounted for small ratings | Cable boxes or bushings as agreed |
Documents & next steps
PDFElectrical Power & Distribution Transformers datasheetTypical specifications · Typically 25–2,500 kVADrawings and documents for a specific order are agreed during engineering review.
For a useful first conversation
- System voltage, fault level, load schedule and connection requirements
- Installation environment, cooling, access and enclosure constraints
- Protection, termination, indication and interface expectations
- Applicable project, inspection and documentation requirements
Common questions
A little context before you enquire.
What decides the transformer rating?
The maximum demand of the connected load, its diversity, expected growth and the ambient conditions. Motor starting and harmonic-producing loads are reviewed separately because they can need a higher rating.
Which voltage ratio and vector group should I specify?
Most low-voltage distribution in India uses 11 kV to 433 V with Dyn11. Where a transformer will run in parallel with existing units, the vector group, ratio and impedance must match them.
Do I need on-load tap changing?
Off-circuit tapping suits supplies with a steady level. An on-load tap changer is considered where the supply varies during operation and the load cannot be interrupted for tap changes.
Which standards apply to distribution transformers?
In India the standard for oil-immersed distribution transformers is IS 1180, and IS 2026 covers power transformers. The standards and tests that apply to an order are stated in the quotation.
What site information is needed?
Supply voltage and fault level, load schedule, installation location, access for delivery and lifting, and the cable or busbar connection arrangement.
Where it is used
Application pathways that commonly start with this product class.
- IndustrialProduction facilities and process equipment
- Commercial & multi-siteOffices, retail and distributed operations
