Reliable Power Transformers
Manufacturer of high-efficiency dry-type and oil-immersed transformers for industrial projects.
Transformers are divided into two main types by insulation and cooling method: dry type transformers, which use epoxy resin or air for insulation, and oil immersed transformers, which use mineral oil. Dry type units suit indoor, fire-sensitive installations from 30 kVA to 2500 kVA, while oil immersed units suit outdoor grids and higher power up to 31500 kVA and beyond. Choosing the right type depends on fire safety rules, environment, voltage class, and maintenance budget.
What Is a Transformer and Its Main Characteristics?
A transformer transfers electrical energy between circuits through electromagnetic induction, changing voltage levels without changing frequency. The characteristics of transformers that matter most for selection are:
- Rated power (kVA) — from 30 kVA pole-mounted units to 31500 kVA distribution classes
- Voltage class — 10 kV, 20 kV, 33 kV, 35 kV primary windings are the most common distribution levels
- Insulation medium — epoxy resin (dry type) vs mineral oil (oil immersed)
- Losses — no-load loss and load loss determine lifetime operating cost
- Impedance and noise level — critical for indoor installations near occupied spaces
Dry Type Transformer Types
Dry type transformers use epoxy resin cast coils or vacuum pressure impregnation instead of oil. Common dry type transformer types include:
- SCB10 series — epoxy resin cast, 100–2500 kVA, 10 kV class, standard indoor choice
- SCB11 / SCB12 series — lower losses, improved noise for commercial buildings
- SCB13 series — high-efficiency amorphous-core option, up to 2500 kVA
- SCB14 / SCB18 series — special designs for harsh or high-altitude environments
- SCZB10 / SCZB12 series — dry type with on-load tap changing for voltage regulation
Explore the full dry type transformer manufacturer lineup or the SCB13 dry type transformer series for detailed specifications.
Oil Immersed Transformer Types
Oil immersed transformers circulate mineral oil for insulation and cooling, enabling higher voltage classes and outdoor service. Main oil immersed transformer types:
- S11 series — standard oil immersed distribution transformer, 30–31500 kVA
- S13 series — low-loss upgrade of S11, popular for utility retrofits
- S18 / S20 / S22 series — progressively lower no-load losses for energy-efficiency projects
- SZ11 / SZ18 / SZ20 / SZ22 series — oil immersed with on-load tap changer (OLTC) for stable output under varying load
See the complete oil immersed transformer manufacturer range and the S11 oil immersed transformer series.
Dry Type vs Oil Immersed Transformer: Comparison
| Feature | Dry Type | Oil Immersed |
|---|---|---|
| Insulation | Epoxy resin / air | Mineral oil |
| Fire safety | Excellent — self-extinguishing | Requires oil pit & fire walls |
| Typical location | Indoor: malls, hospitals, data centers | Outdoor: substations, pole/ground mounting |
| Power range | 30–2500 kVA typical | 30–31500 kVA and above |
| Voltage class | Up to 35 kV | Up to 220 kV and beyond |
| Maintenance | Minimal — visual inspection | Oil sampling, DGA tests, sealing checks |
| Cost trend | Higher unit price, lower install cost | Lower unit price, higher civil works |
How to Choose Between the Two Types
Choose a dry type transformer when the unit sits inside or near occupied buildings, fire codes demand it, or maintenance access is limited. Choose an oil immersed transformer for outdoor substations, higher power ratings, and the lowest lifetime cost per kVA. For mixed projects, many plants pair an oil immersed main substation with dry type distribution units near load centers.
Frequently Asked Questions
What are the two main types of transformers?
The two main types by insulation are dry type transformers (epoxy resin or air) and oil immersed transformers (mineral oil). By function they further divide into power, distribution, isolation, and autotransformers.
What is an oil immersed transformer?
An oil immersed transformer winds its coils in a tank filled with mineral oil, which insulates and carries heat away to radiators — enabling outdoor use and power ratings up to 31500 kVA and above in distribution classes.
Which transformer type is safer for indoor use?
Dry type transformers are safer indoors: epoxy resin is flame-retardant, emits no oil mist, and needs no oil containment pits, making them standard in malls, hospitals, and data centers.
How long does each type last?
Both designs routinely serve 20–30 years. Dry type units avoid oil degradation, while oil immersed units depend on oil quality — annual DGA sampling keeps them healthy.
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