When selecting a servo voltage stabilizer, one of the most important decisions is choosing between oil cooled and air cooled variants. Both use the same servo motor and variac mechanism for voltage regulation, but their cooling systems differ significantly — affecting performance, capacity, installation, and cost.
How Air Cooled Servo Stabilizers Work
An air cooled servo stabilizer uses forced air circulation via built-in fans to dissipate heat from the transformer and variac windings. The air flows over the windings and exits through ventilation slots in the enclosure.
Advantages of Air Cooled Stabilizers
- Compact and lightweight design
- Lower upfront cost
- Easy installation — no oil filling required
- Low maintenance — no oil level checks or replacement
- Ideal for indoor, dust-free environments
- Available from 1 kVA to ~300 kVA
Best Applications
Homes, offices, clinics, small workshops, server rooms, retail shops — any indoor installation where loads are moderate and ambient temperatures are controlled.
How Oil Cooled Servo Stabilizers Work
An oil cooled servo stabilizer submerges the transformer and variac in high-grade insulating transformer oil. The oil absorbs heat from the windings and dissipates it through the tank walls and cooling fins (ONAN — Oil Natural Air Natural cooling).
Advantages of Oil Cooled Stabilizers
- Superior heat dissipation for continuous heavy-duty operation
- Higher capacity range: 50 kVA to 2000+ kVA
- Better electrical insulation — oil provides additional insulation
- Suitable for outdoor and harsh environments
- Handles high ambient temperatures without derating
- Longer transformer lifespan under sustained loads
Best Applications
Factories, manufacturing plants, hospitals, large commercial buildings, cold storage, data centres — any installation with heavy continuous loads or outdoor placement.
Comparison Table
| Feature | Air Cooled | Oil Cooled |
|---|---|---|
| Cooling Method | Forced air (fans) | Transformer oil (ONAN) |
| Capacity Range | 1 kVA – 300 kVA | 50 kVA – 2000+ kVA |
| Installation | Indoor only | Indoor or outdoor |
| Maintenance | Fan cleaning, dust removal | Oil level check, periodic oil testing |
| Cost | Lower for small capacities | More economical at high capacities |
| Ambient Temperature | Up to 45°C | Up to 55°C+ |
| Noise Level | Fan noise present | Very quiet (no fans) |
| Weight | Lighter | Heavier (oil mass) |
How to Choose
Choose air cooled if: your load is under 300 kVA, installation is indoors, and you want lower upfront cost. Choose oil cooled if: your load exceeds 50 kVA with continuous duty, installation may be outdoors, or ambient temperatures are high.
ServoKai System manufactures both oil cooled and air cooled servo voltage stabilizers at our Delhi factory. Request a free consultation to determine the best type for your application.